Editor’s note: This article was originally published in the June 2022 issue of The Horse: Your Guide to Equine Health Care.

Biologic, or regenerative, therapies have altered the way many equine veterinarians treat problematic joints. Some of the most mainstream and popular modalities they currently use to manage osteoarthritis (OA) in horses are autologous conditioned serum, autologous protein solution, platelet-rich plasma, and mesenchymal stem cells.

Most biologic therapies involve collecting and concentrating the horse’s natural anti-inflammatory and regenerative proteins or cells so they can be injected into an area of pathology (disease or damage) in the same horse.

Autologous Conditioned Serum (ACS)

Autologous conditioned serum is a cell-free extract of whole blood that has been processed to contain high concentrations of interleukin-1 receptor antagonist protein (IRAP), a naturally occurring anti-inflammatory protein within the body. It is marketed under the trade names IRAP and IRAP II.

When preparing ACS, veterinarians collect venous blood in a proprietary syringe system that encourages porous glass beads to bind with white blood cells. During an incubation process the bound white cells release high concentrations of IRAP. The veterinarian then draws the serum off into small portions and freezes it for future injection into arthritic joints. In clinical studies of ACS, researchers have reported improved synovial membrane (joint surface lining) health, stimulation of natural IRAP production, and improved lameness.

Platelet-Rich Plasma (PRP)

Platelet rich plasma is blood plasma that’s been centrifuged or filtrated to have a higher concentration of platelets than whole blood. Many horse owners are familiar with PRP and its use in tendon and ligament injuries; however, veterinarians are using it more regularly for treating joint disease.

One of platelets’ roles in the body is to modulate tissue healing. They do so by releasing growth factors and signaling molecules that initiate repair and promote anabolic (supporting tissue growth) effects. Veterinarians have capitalized on this ability by injecting high concentrations of platelets directly into damaged or inflamed regions. Because many PRP systems allow for stallside preparation, it is a convenient option for immediate treatment without the hassle of incubation or culturing in the lab, as is the case with ACS and stem cell preparation, respectively.

Historically, equine veterinarians have primarily used PRP to help treat soft tissue injuries. More recent work has led to intra-articular (in the joint) use with promising results. Although researchers have demonstrated how platelet-derived products work in vitro (in the lab) and veterinarians have seen promising anecdotal results in vivo (in the live horse), they’ve yet to produce evidence-based confirmation of its clinical efficacy.

Mark Revenaugh, DVM, owner of Northwest Equine Performance, in Mulino, Oregon, says the main factors standing between researchers’ ability to gather objective data and establish a consensus on PRP’s efficacy are the high variability among preparation systems, individual patient reactivity to the product, and an unknown ideal concentration of platelets for particular injuries.

“Most practitioners can’t always check how many platelets are being used,” he says. “Depending on the system, one veterinarian may be using 100,000 platelets/milliliter and another veterinarian may be using 1 billion platelets/milliliter. These are not the same treatments, even though both are called PRP. I would love to see an industry standard develop.”

Overall, PRP’s positive anecdotal results and relatively easy preparation make it a useful option for treating osteoarthritis (OA) in horses.

Autologous Protein Solution (APS)

Autologous protein solution (marketed under the trade name Pro-Stride) is essentially a hybrid of ACS and PRP. Its two-step stallside preparation process involves separating whole blood and sequestering white blood cells and platelets in a small fraction of plasma. The veterinarian then concentrates the separate blood components by filtration, leaving a solution of white blood cells, platelets, and serum proteins that provides the anti-inflammatory mediators of IRAP and the platelet-derived growth factors of PRP.

In a 2014 study out of The Ohio State University, researchers revealed that an intra-articular APS injection can significantly improve lameness, weight-bearing symmetry, and range of joint motion in horses that don’t have severe lameness or significant compromise to the joint structure.

Mesenchymal Stems Cells (MSCs)

Mesenchymal stems cells are adult stem cells that can direct regeneration and repair of damaged tissue. Veterinarians have used this type of stem cell as a treatment strategy for equine soft tissue injury for some time; it’s only recently that veterinarians have begun using them to treat OA, and it’s not fully clear how they work in this capacity. Researchers working on early stem cell studies hoped to establish evidence that stem cells injected into regions of injury would develop into the respective tissue. While this hypothesis proved to be incorrect, continued research has revealed that these cells might instead have anti-inflammatory effects and the ability to recruit other stem cells to the area that could, in fact, heal damaged tissue.

The two most common forms of mesenchymal stem cells are adipose (fat)-derived and bone-marrow-derived. Some study results have shown that bone marrow sources yield smaller concentrations than–but are superior to–adipose sources in their ability to differentiate into musculoskeletal tissue. Some encouraging data supporting the use of mesenchymal stem cells for treating OA exists, but researchers have only published a small number of studies with promising results. Equine veterinarians have used MSCs to treat intra-articular soft tissue injury (meniscal and cruciate damage—cartilaginous tissues and ligaments that support the stifle), with successful anecdotal results. They’ve reported more variable outcomes when using it for primary intra-articular injuries.

Carter Judy, DVM, Dipl. ACVS, staff surgeon at Alamo Pintado Equine Medical Center, in Los Olivos, California, says he currently prefers to use PRP and APS for OA treatment over MSCs. However, he admits there is much to be discovered. “What will be interesting to see is how manipulating the cells and providing them with different signals and markers can make their efficacy much more potent and focused,” he says.

Take-Home Message

When weighing treatment options for horses with OA, veterinarians should base their decision to use a certain biologic modality on its cost, availability, and how a horse has responded previously.

“Our knowledge base of how the biologics work is improving, but we are in the infancy of understanding,” Judy says. “Much of the use is based on the clinical response as much as is it on the scientific data.”

Enteroliths are a type of foreign body that can be found in horses’ intestines and are one possible cause of colic, or abdominal pain. Unlike sand or gravel, which horses ingest when they are grazing or eating outside, enteroliths develop when mineral deposits form in concentric layers around a central nidus, such as a piece of wire, small stone, twine, etc., in the large colon (the stretch of intestine between the cecum and the transverse colon). Horses can either have one enterolith (usually round and large) or multiple (often tetrahedral in shape, meaning they have angles or corners).

What Causes Enteroliths?

The cause behind enteroliths—and, especially, why some horses develop them but not others—is still not fully understood. Feeding high levels of alfalfa hay, particularly in California or other locations out west, has been associated with enterolith formation. Decreased turnout and limited access to pasture also have been linked to their development, possibly because of decreased intestinal motility or increased ingestion of alfalfa when stalled. Certain horse breeds (Arabians, Morgan horses, American Miniature horses, and Saddlebreds) have been shown to be more at risk for forming enteroliths.

Enteroliths cause problems when they get large enough that they begin to pass into the transverse or small colon. The diameter of the transverse and small colon is much smaller than the adjacent large colon, so the enteroliths become wedged. Once wedged they block food and gas from traveling out of the intestine, causing abdominal pain and signs of colic.

Some horses with enteroliths could have a history of recurrent colic (repeated colic episodes) due to enteroliths intermittently blocking the intestine and then other times allowing food and gas to pass normally. When the enterolith becomes completely wedged the horse will show signs of severe colic due to gas distension. If the enterolith is large enough and puts pressure on the intestine, it can cause necrosis of the intestinal wall in that area and lead to leakage of feces into the abdomen and secondary infection. In these cases horses show lethargy, decreased appetite, and fever, eventually progressing to signs of sepsis (a life-threatening systemic inflammatory response to infection) and shock. Due to how firmly enteroliths become lodged in the intestines, the treatment for enteroliths is always surgery.

Diagnosis

Veterinarians usually diagnose enteroliths at the time of colic surgery, when the colic signs do not respond to medical treatment, and/or the horse’s colon becomes distended with gas due to blockage by the enterolith. Abdominal X rays can be performed, but in most cases enteroliths are hidden by the large amount of tissue in the horse’s abdomen, making them difficult to detect.

Prevention

If your horse has had enteroliths before, veterinarians recommend taking preventive measures, because there is some evidence they can form again. In these cases, avoid feeding alfalfa and provide as much turnout on pasture as possible.

If at any point you see what looks like an enterolith in your horse’s manure, tell your veterinarian, because the presence of one enterolith (especially if it has a tetrahedral shape) often means there are more in your horse’s intestines. And if your horse shows signs of colic, you should always contact your veterinarian immediately.

Veterinarians routinely perform suspensory ligament branch ultrasounds during prepurchase examinations of young Thoroughbred racehorses. However, they do not have much clear data on what constitutes a normal suspensory ligament branch. Frances Peat, BVSc, PhD, Dipl. ACVSMR, of the Orthopedic Research Center, C. Wayne McIlwraith Translational Medicine Institute at Colorado State University, in Fort Collins, Colorado, collected data from 969 ultrasound exams to establish reference ranges for forelimb suspensory ligament branches. She presented the results at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida.

Studying Thoroughbred Suspensory Ligament Branches

Peat said her goal was to define the normal appearance of suspensory ligament branches, identify common pathology, and determine any association between specific lesions and racing performance as well as association with radiographic changes in the sesamoid bones. This data could help veterinarians more accurately determine which horses are at risk of future injury or poor performance.

In total, she and her colleagues performed ultrasound exams on 593 sales yearlings and 376 sales 2-year-olds. During the exams, they assessed cross-sectional area of the medial and lateral (inside and outside) suspensory ligaments, width, periligamentous (around the ligament) tissue thickness, fibrillar pattern grade (0 to 3), hyperechoic foci (dark abnormality) grade, and sesamoid bone surface grade (yes or no).

They defined Grade 0 fibrillar pattern as a ligament with homogenous echogenicity (brightness) and uninterrupted fibrillar pattern. Grade 1 showed small areas of subtle irregularity, appearing as indistinct hypoechoic (darker) regions. Grades 2 and 3 showed moderate to severe hypoechogenicity and/or disrupted fibrillar pattern.

The researchers analyzed associations between ultrasonographic changes and racing performance from 2 to 4 years of age. Key findings relative to the fibrillar pattern were:

• The cross-sectional area of the medial branch of the suspensory ligament was consistently larger than that of the lateral branch;
• Cross-sectional area increased with fibrillar pattern grade, with Grade 3 lesions having the most enlarged branches;
• The prevalence of Grade 1 (mild) fibrillar pattern was 21% in yearlings and 29% in 2-year-olds;
• Grade 2 fibrillar pattern was seen in 8% of yearlings and 10% of 2-year-olds, and Grade 3 fibrillar pattern was seen in 1% of yearlings and 4% of 2-year-olds.

In some yearlings ultrasound data was available when they re-presented as 2-year-olds. Most of those horses (93%) either remained fibrillar pattern Grade 1 or improved to Grade 0 by the 2-year-old sale. However, one-third of yearlings with Grade 2 fibrillar pattern change progressed to a Grade 3 by the 2-year-old sale.

The Effects of Suspensory Changes on Horse Performance

Peat and colleagues also evaluated the effect of fibrillar pattern on racing performance, including eight measures of performance such as starting at least one race by 5 years of age, total number of starts, earnings per start, etc.

They only considered Grade 3 fibrillar pattern clinically important in reference to racing because those horses had a 0.8 probability of racing (i.e., an 80% chance they’d race), compared to 0.9-0.92 (a 90-90% chance) for horses with Grades 0-2 fibrillar pattern. They associated the presence of Grade 1 fibrillar pattern with significantly higher earnings per start compared to those with a higher grade.

The researchers concluded Grade 1 fibrillar pattern does not seem detrimental to racing performance—a key finding given its high prevalence in yearlings (20%) and 2-year-olds (30%). However, Grade 3 fibrillar pattern has a clinically important detrimental effect on racing.

Take-Home Message

Veterinarians frequently ultrasound suspensory ligament branches during Thoroughbred prepurchase exams but, until now, they’ve lacked clear agreement on what qualifies as normal. Researchers found Grade 1 fibrillar changes common and not linked to poor outcomes—in fact, they correlated with higher earnings per start. However, horses with severe changes had a significantly lower probability of racing. This research offers context for interpreting suspensory ultrasounds, helping veterinarians identify which horses are likely to stay sound—and which might be at risk for injury or poor performance.

Influenza in horses is typically caused by the H3N8 subtype of type A influenza virus. The H3N8 subtype circulates in equids worldwide and its infection often results in mild to severe respiratory disease. In addition to the H3N8 subtype, another influenza A subtype, H7N7, was also identified in horses in the 1950s. After a more than two-decade circulation in horses, H7N7 is believed to have become extinct, probably since 1979. In this regard, equids are unique in that only a single influenza virus, H3N8, is known to currently infect them. Humans and swine are infected by multiple subtypes of influenza A virus.

Current Knowledge About Highly Pathogenic Avian Influenza Virus (HPAI) H5N1 in Equids

Despite the consensus in the equine infectious disease research field that equids are not normally a host species of highly pathogenic avian influenza (HPAI) H5N1, very rare spillover events of HPAI H5N1 in equids over the past few decades occurred in donkeys and horses, respectively. In 2009, HPAI H5N1 was successfully isolated from diseased donkeys with influenza-like symptoms in Egypt. The antibodies to HPAI H5N1 were also detected in 27 out of 105 donkeys involved in this H5N1 outbreak. The combination of seroconversion and virus isolation data provides good evidence that equids are susceptible to infection by HPAI H5N1. Furthermore, a serosurveillance study in 2020 showed low level titers of H5 specific antibodies in wild asses (Equus hemonius hemonius) in Mongolia. Most recently, a comprehensive serosurveillance study of 2,160 equine blood samples collected from July to October 2021 from Mongolian horses, confirmed two samples positive for antibodies against H5N1 by using an array of different antibody assays. This latest serology data appears to continue a theme that equids are susceptible to HPAI H5N1 infection. Considering the low prevalence, it is very likely that HPAI H5N1 may not undergo an efficient transmission in horses, and horse-to-horse transmission may not occur.

Possibly, horses infected with HPAI H5N1 may not show any clinical symptoms. If so, despite the silent infection, HPAI H5N1 virus, when replicating in horses, may encounter seasonal H3N8 virus in the same horse. Such co-infections can create an environment to facilitate swapping genetic segments between the two subtypes and generate a new variant. Such a variant might have the transmissibility of the H3N8 parent and the virulence and novelty to the immune system of the H5N1 parent, which would enable the new virus to escape vaccination-mediated immunity, readily spread among horses, and could cause severe respiratory disease in horses and, potentially, in in-contact humans as well.

To protect equine health, HPAI H5N1 research and diagnosis in horses is critically needed so a potential threat of HPAI H5N1 can be identified before it can jump and spread in horses.

Rapid Response to HPAI H5N1’s Threat in U.S. Horses by the University of Kentucky Gluck Equine Research Center

Since late March 2024, the unprecedented spread of HPAI H5N1 in U.S. dairy cows raises critical questions about the virus’s potential to cross species barriers to infect and cause disease in other agricultural animals, including horses.

To investigate whether U.S. horses are susceptible to HPAI H5N1 infection, we and our collaborators across the country conducted a nationwide serosurveillance study involving 1,462 equine serum samples that were collected between July 2024 and February 2025. Samples were obtained from diverse geographic locations, with most samples from Minnesota, Nebraska, Kansas, Indiana and Kentucky, as well as 23 other states.

Using the IDEXX influenza nucleoprotein (NP) antibody competition ELISA, we found 653 samples (45%) tested positive for NP antibodies (produced by either H5N1 or H3N8). When these NP antibody positive samples were screened in the ID Screen influenza H5 antibody competition ELISA, we identified one sample positive for H5 antibodies. Further validation of the 653 NP antibody-positive samples with the hemagglutination inhibition (HI) assay showed that 641 out of 653 NP antibody-positive samples had detectable HI antibody titers against equine H3N8 virus, indicating these horses were previously vaccinated or infected with this subtype. Finally, none of the 653 NP antibody-positive equine serum samples were positive in the H5N1 HI assay whereas bovine H5N1-positive reference sera were successfully detected.

The current data from our study that is still in progress show that only one out of 1,462 equine serum samples is positive for antibodies to H5 antibodies, indicating that the chance of HPAI H5N1 spillover to U.S. horses is very low. Nevertheless, considering an extremely expanded list of host species that can be infected by HPAI H5N1 with fatal outcomes plus the fact that the HPAI H5N1 virus is mutating rapidly, scaling up H5N1 surveillance efforts in U.S. horses especially in regions where H5N1 has extensively circulated in bovines, is critically needed towards better understanding of equine susceptibility to HPAI H5N1 infection.

Editor’s note: This is an excerpt from Equine Disease Quarterly, Vol. 34, Issue 1, funded by underwriters at Lloyd’s, London, brokers, and their Kentucky agents. It was written by Feng Li, DVM, PhD, professor, William Robert Mills Chair of Equine Infectious Diseases at the University of Kentucky’s Gluck Equine Research Center, in Lexington.

Greater awareness and ongoing research mean fewer foals are being born with this genetic skin condition

Attention stock horse owners: Have you heard of HERDA? For the past 20 years, learning about hereditary equine regional dermal asthenia (HERDA) has been a major goal of stock horse associations and HERDA researchers alike. Up to 3.8% of Quarter Horses—and specifically up to 28.3% of those in the cow horse population—are carriers for this debilitating genetic condition that causes horses’ skin to wrinkle, stretch, and slough. While HERDA horses can be maintained with specialized management, most affected animals are euthanized due to the impracticalities of that care, the inability to be ridden, and painful scarring.

With simple genetic testing, though, owners can find out if their animals are affected by or carriers of HERDA so they can make sound management and breeding decisions. As awareness increases, the industry should see fewer foals born with HERDA—and aim to eliminate clinical cases altogether.

How HERDA Happens

In 1978 scientists first described an unusual super-elastic skin condition and suspected it might have a hereditary link. They were right: In 2007 scientists discovered HERDA arises from a simple mutation on a gene called PPIB, located on Chromosome 1. If a foal inherits that same mutation from both parents, he or she will develop clinical signs of the disease, says Rebecca Bellone, PhD, Veterinary Genetics Laboratory director and a professor at the University of California, Davis.

Scientists traced the mutation back to its origin, a 1944 foundation Quarter Horse colt named Poco Bueno, who sired 405 registered foals. The stallion possessed mutated genetic codes for defective collagen processing. Collagens build connective tissues in skin as well as in cartilage, bones, tendons, ligaments, neurological membranes, and some other tissues. The most obvious effect of these defects is abnormally stretchy and wrinkly skin, with layers often detaching from each other so the skin peels away and sloughs. These gaping skin wounds—along with any other contact wounds—heal slowly and poorly, leaving disfiguring scars.

Owners might first notice frequent lacerations, cuts, or scrapes on young horses eventually diagnosed with HERDA, but the strongest clue appears when these animals are first saddled. At this point they often start to develop wounds along the back and neck. Ultraviolet rays from the sun seem to make the condition even worse, creating new lesions and exacerbating existing ones.

However, because horses have connective tissue throughout their bodies, they might also develop problems elsewhere, says Abby McElroy, DVM, MS, PhD candidate and researcher at the University of Massachusetts Chan Medical School, in Worcester. In particular, researchers know HERDA to be associated with an increased risk of corneal ulcers as well as abnormal heart valves, she says.

“If you have an affected horse, it’s obviously very serious for both the horse and the owner,” says Tammy Canida, registrar at the American Quarter Horse Association (AQHA), whose headquarters are in Amarillo, Texas. “The humane thing to do is put the horses down in most cases.”

It Just Takes Two Alleles

Early research in 2009 revealed 3-4% of Quarter Horses, Paint Horses, and other stock horses probably have the HERDA mutation. However, most of these horses show no signs of disease because they’re merely heterozygous carriers, meaning they have only one copy of the HERDA mutation.

Genetic material comes from both parents equally, as genes from the mother line up in the DNA on the chromosome with matching genes from the father, Bellone explains. Genes often exist in alternate forms, which are called alleles. If an individual gets a different allele from each parent for the same gene, he or she is heterozygous for that gene. If the alleles are the same, though, the individual is homozygous.

Because HERDA is recessive, horses must have acquired the mutated allele from both parents—meaning they’re homozygous—to show clinical signs, Bellone says. Therefore, horses that acquire the mutation from the dam or the sire alone are heterozygous and seem perfectly healthy. Meanwhile, they’re carrying the DNA for the disease. If heterozygous horses are bred to other heterozygous horses, their offspring could inherit the mutated allele from both parents, Bellone says. The resulting cross has a 25% chance of producing a homozygous individual—one with clinical HERDA.

Before 2007 breeders sometimes used trial and error to identify silent HERDA carriers in their breeding stock. But since the development of the DNA test for the HERDA allele, breeders have had a simple tool for recognizing carriers, Bellone says.

“That’s the thing about HERDA; it’s recessive,” she says. “So you can avoid producing an affected animal by knowing what the genotypes of the parents are.”

High-Performance HERDA Carriers

If there’s a DNA test for HERDA carriers, why wouldn’t we just sterilize all mutant-gene horses and eliminate the allele entirely?

The answer might be due to an ironic HERDA twist. As it turns out, there might be a link between a single HERDA allele and good athletic performance. In fact, three of today’s top cutting horse sires are HERDA carriers, says McElroy. So the demand for these genetic lines remains high. And that’s no secret to the AQHA.

“It seems to be in popular lineages that are performing well in the industry,” Canida says.

The reason for that link remains a mystery, says McElroy. “I think that’s a big question within the industry: Why are there so many super-performing carriers?” she says, adding that research is lacking.

Some people in the stock horse industry suspect the mutation might code for more joint mobility in heterozygous horses without causing the deleterious effects of the gene, she explains. “Maybe they have a little bit of the phenotype,” she says, a technical term for observable characteristics.

McElroy wonders if subtle changes in connective tissue might improve performance in athletes in general—both horse and human. “You look at swimmers and gymnasts, for example,” she says. “They’re obviously incredibly hypermobile. But they’re not ill. And for horses working in cutting and reining, that hypermobility would give them a huge athletic advantage.”

Even so, if the allele endows stock horses with a “superpower” that garners many winnings early in the horses’ careers but then leads to bone and joint conditions such as osteoarthritis later in life, it could pose a welfare issue, McElroy adds.

Thus far, scientists have neither studied these questions nor measured the degrees of equine or human joint hypermobility with regard to connective tissue quality. And there has been no research completed on bone and joint health specifically in HERDA carriers. “That’s something that really needs to be studied, in my opinion,” McElroy says. “At this point, it’s unclear if an athletic advantage truly exists. It’s also unclear if any perceived advantage comes from the HERDA mutation or another gene.”

DNA Testing: Quick, Easy, Affordable, and Important

With HERDA carriers’ successful performance careers and breeding popularity, genetic testing has never been more important, our sources say. “The number of carriers right now is astronomical,” McElroy says. “So people really need to make informed decisions before breeding.”

The AQHA and American Paint Horse Association (APHA) agree. To minimize the breeding of homozygous foals, the associations have teamed up with Bellone and other experts to create educational materials and offer easy instructions for owners to have their horses’ DNA tested. A simple HERDA DNA test requires a few strands of mane and costs $45 through the UC Davis Veterinary Genetics Laboratory, or $100 as part of the full AQHA/APHA genetic testing panel.

Since 2015 the AQHA has required that owners of all breeding stallions have their studs’ genetic HERDA information on file and accessible to mare owners. In 2018 the APHA followed suit. Foals can only be registered with the AQHA and APHA if their sires’ genetic information, including HERDA status, is on file with the association.

Being heterozygous doesn’t exclude the stallions from breeding, however. Canida explains that the goals of the test are purely informational. “We always recommend that mare owners ask stallion owners for the information that would impact their breeding choices,” she says. “But we also make it public information, so that they can always pull the record and see it on our files as well.”

The associations do not require owners to test broodmares, but they strongly encourage it—especially when considering breeding to a heterozygous stallion. “If mare owners are aware that the stallion they want to breed to is a carrier, then they need to test the mare to ensure that they don’t produce any affected animals,” Bellone says.

 “We feel that our goal is to educate the members about it so they can make the choices for their breeding barn,” says Canida. “We just want them to be aware of what a horse may or may not have.”

“And under current rules, it will not be eliminated,” she adds. The AQHA’s focus, she says, is on education so as “to avoid getting those (clinically) affected horses.”

Meanwhile, nonbreeding stock can also undergo DNA testing if their owners suspect they’re homozygous or even heterozygous for HERDA, or if they’re just curious, our sources say. Both the AQHA and APHA websites provide educational tools that help owners understand DNA test results and how to manage their horses accordingly.

Importantly, awareness—even of the tests themselves—remains key, stresses Bellone. “If the genetic test exists, but people aren’t using it, it’s not helping,” she says.

Managing (and Surviving) HERDA

While the main goal is preventing the birth of any homozygous foals, the harsh reality is such births persist, our sources say. Our sources say most affected adult horses end up being euthanized, some are shipped for slaughter, and a few are rescued by nonprofit organizations. Some homozygous mares serve as embryo transfer recipient mares. Occasionally, owners keep their own homozygous foals as well-protected pets. McElroy says she recalls the case of a homozygous horse that successfully worked cattle for eight years—although it’s possible the horse had, for reasons unknown, a milder form of the disease.

If their quality of life permits it, HERDA horses could be kept in indoor conditions during daytime hours to prevent sun rays from breaking down collagen, she says. Owners would have to ensure the environment is low-risk for contact injuries—even rubbing against surfaces—and for insect bites. “There are owners who have kept these horses going for many years, keeping them inside during the day, turned out at night with intensive fly management, staying away from … anything that’s going to traumatize the skin,” McElroy says.

Management methods for similar connective tissue disorders in humans and smaller animals have progressed in recent years because these individuals’ environments can be more easily controlled. Unfortunately, that’s not the case for horses. “We just don’t know much about keeping these horses going longer,” she says.

“At this point, we don’t have a lot of therapies or treatments,” McElroy says. “It would really just be intensive management.”

HERDA on the Horizon

In the past two decades, HERDA researchers have mostly studied the condition’s effects on the skin, but they’ve started looking into its effects elsewhere in the horse’s body. For example, homozygous horses have thinner corneas with more frequent ulcers, and they have weakened heart valves.

“Collagen is everywhere, so it affects every bodily system,” says McElroy, who studies HERDA as an equine model for Ehlers-Danlos syndrome—the general HERDA analog affecting humans, rabbits, cats, dogs, cattle, sheep, and mink. “There’s a lot we don’t know about. Do they have bone fragility? What’s going on with their GI tract? Are they more likely to colic? Are they more likely to have bladder ruptures as foals?” Her own work has focused on the nervous system and confirms—like in humans with Ehlers-Danlos Syndrome—HERDA horses have abnormal spinal cord regions in the sacrum area, although the physical implications remain unclear.

Scientists are also considering whether HERDA affects some horses more severely than others—with some, like the exceptional HERDA working cow horse, having such mild disease it might even go unnoticed. “For me the question has always been, ‘Are there some underlying genetics that can protect some horses?’ ” Bellone says. “And also, ‘Is there any hope of testing for something like that, or doing any kind of research on it?’ ” To her knowledge, at this time, there is not.

An upcoming research area for such diseases is gene therapy, which essentially involves injecting the healthy allele via a viruslike vector into newborns, effectively replacing the bad allele, McElroy says. Better yet, gene therapy could start after genetic testing of the embryo. While progress is underway for humans, the astronomical price of such therapy—reaching seven figures—is likely to preclude its commercial use in horses. “It would be more like on a research basis,” she says, adding that costs might drop over time and especially with prenatal treatment.

Meanwhile, scientists and associations are continuing to focus on awareness, making sure owners understand what HERDA is and how to prevent it through DNA testing and wise breeding. Efforts so far have been fruitful, McElroy adds, with a drop in the number of homozygous foals born.

Whether the incidence of the allele itself is dropping remains hard to say, notes Bellone. With the steep increase in testing, it’s difficult to compare today’s rates with those from the mere hundreds of horses tested 15 years ago. Even so, ongoing analyses suggest there’s a trend toward a drop in allele frequency, she explains.

“We need to continue that push for education and make sure that people really understand the genetics of a recessive disease, and make sure they understand the risk of carrier-to-carrier matings,” McElroy says.

Take-Home Message

As scientists progress in their understanding of HERDA, so must the owners and breeders managing and producing the horses that carry the alleles responsible for this recessive disorder. With improved awareness and ongoing investigation into the whole-body effects of this disease, the industry is striving toward prevention and—potentially in the distant future—a hope for therapeutic management.

With thousands of equine supplements on the market—ranging from joint support and digestive aids to calming formulas and coat enhancers—horse owners often look to veterinarians for guidance on what their animals might need. Veterinarians can help them determine when supplements are necessary for their horses, which ones are appropriate, and how to avoid ineffective or potentially harmful choices.

Start With the Forage

Carey Williams, PhD, equine extension specialist and professor at Rutgers University, in New Brunswick, New Jersey, says supplement discussions should always begin with the horse’s core diet in mind.

Forage should be the foundation, Williams says, followed by a concentrate or other commercial feed appropriate for the horse’s age, workload, and physiological status. For example, a broodmare or growing horse needs a different feed than a performance or pleasure horse. “Then you can decide—is there (a specific concern) that a supplement might help with?” she says.

If the diet is already balanced and the horse has no underlying issues, Williams says supplements might not be necessary at all.

Making Informed Equine Supplement Decisions

Once they’ve identified a need, veterinarians can help clients evaluate product options by focusing on transparency and research. “Some companies won’t be doing their own research, but they might cite published studies on ingredients in their product,” Williams says.

Veterinarians should direct owners to supplements with labels that include detailed ingredient lists, recommended dosages, and explanations of function. Vague phrases such as “proprietary blend” can be red flags. “The more specifics a company provides, the more confident I am in their product,” she says.

She also advises veterinarians to recommend ingredients rather than specific brands if they do not have a brand with which they are comfortable. “If you’re not familiar with a company, suggest functional ingredients like omega-3s from a particular source or specific antioxidants,” says Williams. “That way, the owner can do some research on their own or consult a nutritionist.”

Evaluating Equine Supplement Quality and Avoiding Risk

Quality control ranks among the most important factors to consider when choosing a supplement for your horse. Veterinarians can help clients look for companies that publish their testing protocols or quality assurance processes on their websites. “Reputable companies will show how they test their products, what methods they use, and how they ensure consistency,” Williams says.

She adds that cost can be a helpful indicator, though not a guarantee, of quality. “You do often get what you pay for,” she explains. “If a supplement is dramatically cheaper than others with similar ingredients, it should prompt questions. Is it underdosed? Has it been sitting on a shelf for years? Is the company cutting corners?”

She finds low-cost supplements from companies with limited public information or no customer support especially concerning. “Reputable companies are happy to discuss their product with you, including safety testing and research on it,” she says. “They spend a lot of money doing this, so they want everyone to know.”

Navigating Client Conversations About Equine Supplements

When a supplement serves no clear benefit or risks interfering with veterinary treatment, communication becomes essential. Williams often works alongside veterinarians during consultations to evaluate horses’ full diets and provide evidence-based recommendations.

“In cases where the vet suspects a supplement is doing more harm than good, we’ll go over the label with the client together,” she says. “Sometimes it’s not about the brand, but about the dose being too low to be effective, the supplement interacting with a medication, or they are feeding several products with overlapping ingredients.”

To help owners feel comfortable making changes to their horses’ supplement regimens, Williams recommends gradual adjustments. “I always suggest decreasing the dose first,” she says. “If they see no change, they’re usually more open to discontinuing it. It’s a good way to determine if the supplement is having an effect or not.”

Working With Equine Nutrition Professionals

Not all veterinarians are confident advising their clients about equine nutrition, which is where collaboration with a nutritionist can be helpful. Williams encourages veterinarians to contact equine extension specialists at their states’ land-grant universities, many of whom offer free or low-cost consulting.

“If a vet isn’t confident evaluating a ration, they can call someone like me,” she says. “Every state has cooperative extension, and we also have a national network. If I get a call from another state, I can help them out myself if their field is not nutrition, or I can refer them to a trusted colleague who can.”

Understanding Equine Supplement Regulation Gaps

Unlike prescription medications, equine supplements are not subject to FDA regulation, and manufacturers do not need to demonstrate efficacy before products reach the market. Veterinarians should communicate this to clients so they understand the importance of thoroughly researching supplements before purchasing them, says Williams. “That’s why it’s so important to stick with companies that are transparent, publish their ingredient lists, and explain their quality control processes,” she adds.

Williams also recommends that clients call companies directly to ask questions. “A reputable company should be able to explain what’s in their product and why,” she says. “If they avoid your questions or don’t respond at all, that’s a problem.”

Take-Home Message

Veterinarians can help clients make responsible, informed decisions about nutritional supplements for their horses. By evaluating the base diet, recommending evidence-based ingredients, and collaborating with qualified nutritionists, they can provide practical guidance grounded in science.

“There are good supplements out there,” Williams says. “But they should be used intentionally and with a clear purpose. It’s about solving a problem—not just adding something extra because they read about it online.”

Over the last two decades, West Nile virus (WNV), an orthoflavivirus transmitted by mosquitoes, has become endemic on all continents except Antarctic and continues to be a major threat to the health and well-being of both horses and humans. The virus had an explosive emergence in North America in 1999, followed by rapid expansion throughout the U.S. and parts of Canada over the first five years, which resulted in often catastrophic disease in over 25,000 U.S. horses. With the rapid deployment of vaccines, the U.S. equine caseload decreased dramatically by 2006.  

Once established in a new area, reported cases in humans and horses, depending on vaccine status, will occur yearly but can vary in intensity from year to year. The virus can also cause explosive outbreaks in new locations or among those that have only experienced sporadic cases.  

While most mosquito borne viruses are typically associated with tropical or subtropical climates with high precipitation, WNV is endemic in a variety of climates, including temperate, continental and semi-arid areas. The continental U.S. and Europe are two great illustrative examples of the adaptability of this wide-ranging virus. During the last 10 years, 2,484 cases of equine WNV were reported in 46 U.S. states. Climate did not appear to be an issue since the states reporting the highest number of cases of WNV infection (Texas, Pennsylvania, California, Colorado, Utah and Montana) spanned all six U.S. National Oceanic and Atmospheric Administration defined climate regions. In Europe, most WNV activity in equids was initially reported in regions around the Mediterranean basin, however, during the past two decades, WNV activity was reported in more central and northern countries and regions such as Western France (Landes), Eastern Austria (Vienna), Hungary, and Northeastern Germany (Berlin). In 2024, a spike in the number of cases occurred with 494 affected premises reported in 10 countries, representing a 50% rise in reported equine cases over the two previous years. Northern Germany had the highest number of reported cases, approximately 200, with disease occurring in two federal states where activity had not been previously reported. There were 55 affected premises, typically with one or two cases, reported in Austria, a country in which the previous highest case count was four in 2019.  

WNV outbreaks are not confined to North America and Europe. Outbreaks have been reported in Central and South America, the Middle East and Australia. Australia is home to WNV lineage denoted as Kunjin virus, or WNV subtype 1b, which underwent a change in virulence resulting in a severe WNV outbreak in 2011 affecting over 1,000 horses.  

Nine lineages are now recognized with at least three (Lineage 1a, L1b and L2) associated with neurological disease in horses and cause similar clinical signs and pathology. When data is analyzed across multiple studies, mortality is about 30-40% for all lineages. Neurological disease, often with severe outcomes, remains the primary clinical presentation in the nonvaccinated horse.  

Contrary to observations for other viral epidemics, the virulence of this virus has not declined over time. West Nile fever is not recognized in the horse and all clinical manifestations observed are neurological. Affected horses had one or more neurological abnormalities consisting of changes in mentation (30%), locomotion (70%) and/or cranial nerve deficits. A common feature (approximately 80%) of WNV in horses was the presence of muscle tremors or fasciculations. In an analysis of pooled data from 14 studies (2,182 horses), approximately 30% of horses became recumbent necessitating euthanasia for humane reasons.  

Many studies examined risk factors for disease, including intrinsic factors such as age, sex or breed predilection with pooled analysis demonstrating no inherent bias. While early studies suggested an increased risk of mortality for older horses associated with underlying health issues, in fact all unvaccinated horses less than 1 year old infected with WNV died. Multiple extrinsic factors such as hair coat, housing, use of fans, etc. have been analyzed and were found equivocal to disease. Vaccination overrides all risk factors in terms of effect on susceptibility to disease.  

With no specific antiviral therapies, vaccination is the only intervention that successfully prevents severe neurological disease in the horse. Currently all marketed vaccines have comparable efficacy (over 90%) against known lineages that infect horses, and vaccines are marketed in North America, the United Kingdom and Europe. The American Association of Equine Practitioners identifies WNV vaccination a core component, which indicates that horses should be immunized annually to prevent disease. Vaccination against WNV is considered a ‘best practice’ under the guidelines provided by The Equine Infectious Disease Surveillance of the United Kingdom. While annual boosters are recommended, horses are not fully protected unless the initial immunization consists of two injections given four weeks apart. Foals must receive an additional booster 10 to 12 months prior to the next mosquito season or eight weeks after the second dose.  

With continuous expansion of this virus within and beyond an established endemic area, coupled with (international) travel of horses in and out of these areas, veterinarians and owners should consider all horses irrespective of location and climate at risk for WNV disease if not vaccinated. 

Editor’s note: This is an excerpt from Equine Disease Quarterly, Vol. 34, Issue 1, funded by underwriters at Lloyd’s, London, brokers, and their Kentucky agents. It was written by Maureen T. Long, DVM, PhD, Dipl. ACVIM, emeritus professor at the University of Florida’s College of Veterinary Medicine, in Gainesville. 

The Kester News Hour at the annual American Association of Equine Practitioners Convention highlight key advancements in equine research worldwide. In 2024’s edition Carrie Finno, DVM, PhD, Dipl. ACVIM, professor of veterinary genetics and the Gregory L. Ferraro Endowed Director of the Center for Equine Health at the University of California, Davis, and Katie Seabaugh, DVM, Dipl. ACVS, ACVSMR, associate professor of equine sports medicine and rehabilitation at Colorado State University, in Fort Collins, shared their top picks from recent studies in their areas of practice interest.

Studying Graying Speed and Melanoma in Horses

Finno began with research by Rubin et al. (2024), in which researchers identified a genetic variation in horses that determines their greying speed and melanoma incidence.

“Graying is caused by a duplication of a 4.6 kb (kilobase, a unit of measurement used to help designate the length of DNA or RNA) intronic sequence in syntaxin 17 (STX17),” said Finno. “If horses have one copy of the variant, then they are not gray. Gray horses with two copies of STX17 gray slowly and have lower rates of melanoma but, if a horse has three copies, then they are the fast-graying horses linked with melanoma.”

For example, if a gray mare has the genes G3/G1 and the gray stallion is G3/G1, then the foal could be G3/G3, meaning he or she will gray very fast and has a higher likelihood of developing melanoma. The results could lead not only to better identification of horses likely to gray early or pass on gray-with-age genes but also to a better understanding of how the mutation affects horses’ health.

Detecting Atrial Fibrillation in Horses

In the second study Finno covered (Vernemmen et al., 2024), researchers described a method for veterinarians to detect atrial fibrillation in horses using an implantable loop recorder (ILR).

The ILRs can be placed under the skin in the left lateral thorax overlying the heart, said Finno. Practitioners use these to detect arrhythmias as a possible cause of collapse, poor performance, or monitor for atrial fibrillation (AF) recurrence in a research setting. The device can now collect information and email the clinician, improving the speed with which AF can be identified.

“Be aware that some false positives can be a result of bradycardia (when the heart beats slower than normal) rather than AF because it is a human product,” said Finno. “And we need to appreciate that AF is likely genetic.”

Identifying A Cause of Neck Pain in Horses

Seabaugh presented a study (Hendersen et al., 2024) in which researchers described the incidence of neck pain without neurologic disease in horses with transposition of the ventral lamina from C6 to C7 of the cervical vertebrae.  

“The ventral lamina is part of the transverse process, and this ventral aspect of C6 can move to the C7 vertebra,” said Seabaugh. “When located on C6, the longus colli muscle attaches to the ventral lamina, which is a cervical flexor. Movement of the transverse process likely affects the biomechanics of the neck.”

In the retrospective study, researchers looked at radiographs taken from 2020 to 2022, including a total of 135 horses. Reasons for radiographs included routine neurologic exam, neck pain, and performance-related behavior changes.

Key findings were:

1. The researchers saw transposition in 20% of the horses that was not significantly associated with a final diagnosis, meaning an equal number of horses with or without the transposition fell into each diagnosis; and
2. Transposition was more common in horses that demonstrated pain during palpation of the neck (31%) than those without pain (18%).

Additionally, 63% (17 out of 27) of the horses with transposition were Warmbloods.

Prevalence of Neck Pathology in Warmblood Horses

Looking at Warmbloods more closely, Seabaugh presented a second study (Sue Dyson et al., 2024) where researchers described the prevalence of C6 and C7 transposition in the breed.

“This study included only Warmbloods: 127 controls and 96 horses with neurologic abnormalities, neck pain or stiffness, or neck-related forelimb lameness,” Seabaugh said. The researchers found 24.2% of horses had C6 and C7 transposition. Horses without neurologic issues (the controls) were more likely to have this variation than those with neurologic abnormalities.

“The conclusion from both studies was that there is no association between C6/7 transposition and neurologic disease, and it is just a variant occurring in up to one-quarter of all horses,” said Seabaugh.

Updated ACVIM EHV Consensus Statement

Finno broke down the updated ACVIM consensus statement for equine herpesvirus (Lunn et al., 2024) for the audience.

Three key takeaways from the new guidelines included:

1. Researchers have seen minimal evidence that the vaccine protects horses against equine herpesvirus-1 infection, but they still recommend vaccinating.
2. Pharmacological treatments have minimal effect (except valacyclovir if administered in advance).
3. In large outbreaks nasal swabbing typically suffices for diagnosing affected horses; however, when abortion occurs on the premises, veterinarians need to test blood samples.

In a study following the herpesvirus outbreak in Valencia, Spain, “Sixty-eight percent of horses with neurologic disease returned to exercise, and over half returned to full performance,” said Finno. “But the less ataxic they were on presentation, the more likely they were to fully recover. If there was urinary and vascular compromise, then they were more likely to be euthanized.”

Joint pain and osteoarthritis (OA) represent one of the leading causes of performance loss in equine athletes, affecting around 60% of the overall population. Chronic inflammation may cause permanent changes in joint function, leading to long-term pain, swelling and decreased range of motion, among other debilitating symptoms.  

Many of the current OA treatments are management tools that prolong function, generally without modifying OA progression. The most common treatments include non-steroidal anti-inflammatory drugs (NSAIDs) and oral joint supplements that target cartilage repair or protective pathways, as well as joint injections with corticosteroids or newer orthobiologics, both of which are anti-inflammatory. Unfortunately, many of these treatments are associated with other adverse effects, especially when used long-term. 

Several novel treatments to reduce joint inflammation with minimal side effects have been proposed within the scientific community. One such treatment is cannabidiol (CBD), a non-psychoactive chemical compound found in Cannabis sativa (colloquially known as hemp). CBD is known to target the endocannabinoid system, a complex network of several biological systems that affects many physiological processes, including but not limited to, pain perception, appetite, mood, learning and immune function. Within the context of OA, CBD has been found to inhibit the production of substances that increase inflammation, decrease sensitivity of pain-associated receptors and modulate an overactive immune system. Anecdotally, many people claim the benefits of CBD, but more research is required to accurately quantify and qualify its potential benefits and risks. This is especially true within the equine community.  

Our work in the Page Laboratory is interested in understanding the potential anti-inflammatory effects of CBD in joints via the implementation of a three-phase project. We aim to improve a chemically induced joint inflammation model such that it will be repeatable and reversible, while still accurately mimicking the body’s physical and biochemical response to inflammation.  

Phase one involves refining the dosage of a proinflammatory compound which will be injected into one knee (carpal) joint, inducing temporary inflammation. Defining an appropriate dosage protocol and taking note of individual horse variability is an important step for developing a reliable experimental procedure.  

Following phase one, the aim of phase two is to identify an appropriate CBD formulation for oral administration. Due to its chemical composition, CBD is not well absorbed by the equine GI tract, with a bioavailability around 10% (e.g. horses will only absorb about 10% of the CBD administered to them). Previous research has found what a drug is dissolved in can make a large difference in systemic CBD levels, and the most effective candidates are usually composed of fats, such as sesame or canola oil. An optimized formulation is necessary to both maximize therapeutic benefit while keeping palatability in mind for horses.  

In phase three, we will combine the findings from the first two phases and analyze the effects of CBD on the drug-induced inflammatory response. A control group will receive no CBD, and the differences between the treated and untreated group will be evaluated. Horses will be evaluated for several parameters, including the presence of biomarkers associated with inflammation both within the joint and systemically throughout the body. The mild lameness that is induced will be quantified via an objective evaluation system that can better detect the subtleties of gait asymmetries when compared to the human eye.  

While other researchers have shown that CBD represents an exciting prospect for the treatment of chronic joint pain, our research should provide additional information on its efficacy for the horse. Our findings may find applications for human medicine given the mechanisms of OA and joint pain in humans often mimic those seen in horses, which is important given that approximately 45% of people will develop some form of OA within their lifetimes. In the end, we hope to provide a better research model for joint inflammation while simultaneously evaluating CBD as a way to manage joint pain in horses. 

Editor’s note: This is an excerpt from Equine Disease Quarterly, Vol. 34, Issue 1, funded by underwriters at Lloyd’s, London, brokers, and their Kentucky agents. It was written by Jenna McPeek, PhD Graduate Student at the University of Kentucky’s Gluck Equine Research Center, in Lexington and Allen Page, DVM, PhD, assistant professor and faculty advisor at the Gluck Equine Research Center. 

In recent years more equine practitioners have gained access to cross-sectional imaging, including MRI and computed tomography (CT). These modalities create “slice” images of structures, providing a three-dimensional view and giving veterinarians the ability to diagnose issues that aren’t always visible on standard radiographs. Practitioners often assess show jumping horses’ fetlocks using MRI and CT because this high-motion joint is a common source of pain in these athletes. Cross-sectional images can reveal various fetlock joint, but determining whether these lesions hold clinical significance or simply reflect normal adaptive changes can be challenging.

Annamaria Nagy, DVM, PhD, of the Equine Department and Clinic at the University of Veterinary Medicine, in Budapest, Hungary, and Sue Dyson, MA, VetMB, PhD, conducted a study to document findings on low-field MRI, fan-beam CT, and radiographs (X rays) in nonlame show jumpers in full work. None of the horses they included had a history of fetlock joint disease.

The researchers most frequently noted CT and MRI changes consistent with the densification of the highly porous bone trabecular bone located in the sagittal ridge and/or condyles of the third metacarpal (cannon) bone. Both the sagittal ridge and condyles are located at the bottom (distal) aspect of the cannon bone where it articulates with the long pastern.

They noted this particular change in 53 (85.5%) of the 62 limbs they studied.

“Densification of the trabecular bone of the medial condyles in the dorsal and palmar aspects was very common, and the densification of the lateral condyle was more pronounced in the palmar aspect,” said Nagy. “Usually, the densification was bilaterally symmetrical, affecting both forelimbs.” In other words, Nagy and Dyson commonly saw clear patterns where this bony densification occurred within the fetlock.

On MRI and CT they also found:

• A focal hypoattenuating lesion (dark abnormality on CT) in the dorsoproximal aspect of the medial condyle in three horses that they were not able to detect on radiographs;  
• A focal hypoattenuating lesion in the dorsodistal aspect of the condyle in one limb that they also could not detect on radiographs;
• A focal hypoattenuating lesion in the palmar aspect of the lateral condyle of one horse that they did not detect on either MRI or radiographs;
• Subchondral (found beneath the cartilage) bone plate thickening in the proximal phalanx—the long pastern bone—in 61 limbs, typically in just one limb per horse;
• Sagittal groove indentation in both limbs of one horse; and
• A focal hypointense signal (low-signal intensity on MRI) in the medial aspect of the sagittal groove in one horse.

“Periarticular (around the joint) remodeling was more evident on CT than MRI and radiographs, and no significant soft-tissue lesions were identified in this study,” said Nagy.

“Trabecular bone densification of the third metacarpal bone was common in nonlame show jumpers,” she added. “While the trabecular bone densification likely reflects adaptive changes to exercise, horses could experience pain in those areas due to increased intraosseous (in the bone) pressure.”

Take-Home Message

Although all horses included in this study were sound, some of the lesions in the cannon bone condyles or long pasterns could cause lameness and become clinically significant over time.

“Future studies collecting longitudinal data (from the same subjects repeatedly over a period of time) on these horses and objective comparison of imaging findings for specific abnormalities are needed,” said Nagy. Other research could include performing objective assessments of bone thickening in these horses, she added.

Professional human athletes experience strain from frequent, rigorous training and performance. They use various complementary therapies to accelerate their bodies’ natural healing process and ease the discomfort they experience so it doesn’t interrupt their performance. Equine athletes might also benefit from a variety of integrative therapies to help them feel and perform their best.

A significant advantage to using complementary therapies is that they are drug-free and most are allowed during competitions. Electroacupuncture, shock wave therapy, Class IV laser therapy, and cryotherapy are an exception because they are not permitted during FEI-sanctioned events. (Always check the rules governing your competition).

While many complementary therapies can be useful and incorporated into a horse’s wellness program, Tracy Turner, DVM, MS, Dipl. ACVS, ACVSMR, founder of Turner Equine Sports Medicine and Surgery, in Stillwater, Minnesota, says he considers the cost/benefit ratio when deciding which to recommend to a client.

“What does it cost to use it?” he asks. “How much benefit will the horse get? That changes based on the scenario and part of the decisions made by the horse’s health-care team, including the veterinarian, horse owner, and trainer.”

He adds that knowing the goal for using complementary therapies is also critical. If you’re trying to help the horse achieve relaxation (which has its benefits), that’s one thing, but if it is to heal an injury, these therapies on their own will not achieve the desired outcome.

“It’s important to have your veterinarian do a whole-horse evaluation,” he says. “I firmly believe there’s no such thing as a single injury. Diagnosing the underlying issues is essential to knowing how the horse might be compensating in other areas (and) to decide what the horse needs, and fitness comes into the equation, too.”

Picking a modality for your horse and your discipline can feel as overwhelming as restaurant menus with too many choices. Here’s a selection of popular treatments for keeping performance horses feeling their best. Use this article to start a conversation with your veterinarian about options that make the most sense for your horse.

Acupuncture

“Acupuncture is a useful, time-tested modality that has a lot of science and thousands of years of use,” says Andris J. Kaneps, DVM, PhD, Dipl. ACVS, ACVSMR. He owns Kaneps Equine Sports Medicine and Surgery LLC, in Beverly, Massachusetts. More of that science appears in the human literature than in equine studies, however. “It’s gradually becoming more widely recognized as a valid treatment in horses,” he adds. (Read about acupuncture and a review of existing research at TheHorse.com/181626.)

“It has very valid support scientifically and anecdotally,” he says. “A key difference between acupuncture and what we call Western veterinary medicine is that the approach is completely different.”

For example, as a Western-trained veterinarian, he palpates for swelling or increased joint fluid, looks for pain with hoof testers, and performs a lameness evaluation for signs of discomfort. In Chinese medicine those factors are important, but practitioners also evaluate the sensitivity of acupoints throughout the body, assess tongue color and moisture, and examine other factors that aren’t in the normal diagnostic approach for Western medicine, he explains.

Kaneps especially likes acupuncture for horses with back pain because of the equine research that supports its use for such cases, and he has seen multiple horses experience significant improvements after treatment.

“As with all complementary therapies, this does not mean I just treat a horse with acupuncture,” he says. “I may use some Western modalities as well as other complementary techniques to reduce back pain in a horse. Using one alone may not do it, but using several together can improve the outcome.”

Spinal Manipulative Therapy

Inflammation of the nerves and other tissues surrounding joints, especially in the spine, can lead to pain and reduced function, especially when the joints are stiff or immobile. Spinal manipulation (described at TheHorse.com/113280) could help restore the range of motion.

“Chiropractic adjustments keep the horse limber and moving to prevent areas of fixation through the neck, back, pelvis, etc.,” says Ed Boldt, DVM, owner of Performance Horse Complementary Medicine, PLLC, in Fort Collins, Colorado. “Like human athletes, when (horses) are in better shape, they are less likely to have an injury.”

In Boldt’s opinion, horses that are not performing optimally are candidates for spinal manipulative therapy. He uses the example of a barrel horse running to the wall (where the horse runs past the barrel and doesn’t slow down to turn) or going flat (leaning on his front end) around the barrel.

A horse that is three-legged lame is not one that would benefit from chiropractic therapy, he says. “Those horses need a diagnosis and treatment plan, and then integrative therapies might be added to help healing,” he explains.

Boldt also believes veterinarians trained in chiropractic care should make the adjustments. Some states allow chiropractors licensed to work on humans to have animals as patients after completing approved continuing education.

“To me, it’s important the vet is involved either doing the treatment or at least approving of the treatment,” he says.

Chiropractic care without an equine practitioner’s examination might worsen a situation. Boldt remembers being called to examine a horse treated by a nonveterinarian, and the horse was getting sorer rather than improving. By watching the horse move and using hoof testers, Boldt identified the horse had an abscess.

In another case an older horse had fallen on an icy hill and injured his neck. The owner brought it to Boldt, who refused to provide an adjustment without radiographs.

“Thankfully, I insisted,” he says. “The horse had a fractured neck, and if I’d just gone in and adjusted the horse there could have been severe consequences.”

Kaneps agrees that equine chiropractic adjustment is a well-tested modality, and those trained in it should perform treatment.

Vibration Plate Therapy

The next time you watch a sporting event, notice how the athletes “jump” around on the sidelines, readying themselves for play. Turner likens the benefits of vibration therapy in horses to those loosening routines.

The gentle motion is believed to increase blood flow, lessen joint pain and inflammation, and warm and loosen muscles, which reduces horses’ muscle tension before a ride. Research findings on the effects of whole-body vibration are mixed. One example is a Michigan State University study in which researchers subjectively found no difference in flexion, stride length, or heart rate after vibration therapy, but horses exhibited behavioral changes such as relaxation and less stress.

In another study, out of Peninsula Equine Medical Center, in California, a researcher found that hooves grew faster after two months of whole-body vibration. Further, this vet and colleagues plus one from Western University of Health Sciences College of Veterinary Medicine observed an increase in back muscle size and symmetry after twice-daily whole-body vibration treatments five days a week for 60 days (Halsberghe et al., 2017).

“In general, horses really like it,” says Gabrielle Solum, DVM, a resident at Equine Sports Medicine and Rehabilitation, in Whitesboro, Texas. “They yawn and relax on there, so it’s a nice therapy for them to have. The biggest thing is if you achieve benefits like increased hoof growth and larger back muscles, it must be used daily and (you need to) recognize that there is no prolonged effect if you stop using the modality.”

Pulsed Electromagnetic Field (PEMF) Therapy

This approach uses pulsating magnetic fields, made by pulsing a small electrical current through wire coils, to jump-start and accelerate normal biological cellular reactions. Most of the information on PEMF therapy is on bone healing. Proponents say PEMF increases circulation and decreases pain and inflammation to accelerate healing.

“It is really good for muscle relaxation … when an animal is relaxed, they hold themself differently, and we want a horse to bear its weight correctly,” Turner says.

Pulsed electromagnetic field therapy is just one type of electrical stimulation treatment. One of Turner’s go-to modalities that also falls into this category is functional electrostimulation (FES), which works to strengthen a muscle that is not being used and can provide pain relief. This mimics nerve patterns signaling the muscles to contract, and he has found it particularly beneficial when an area has been inactive following an injury.

“Functional electrostimulation has a lot of uses,” Turner says. “It can be particularly helpful for horses needing multiple spinal or skeletal adjustments. The electrostimulation helps fatigue the muscles so you can better work on an area.”

Ice/Cryotherapy

Since the dawn of human sports medicine, doctors and surgeons have recommended ice baths to decrease inflammation and reduce pain. Solum says this easy-to-use treatment is underutilized.

“Ice boots are great to use after exercise for 20-30 minutes to decrease inflammation,” she says. “There are a lot of ice boots on the market, but it’s also acceptable to use a bucket of ice if your horse will tolerate it.”

She often pairs ice with heat, especially for horses with back pain or those performing athletically.

“You can place a warm towel on the horse’s back or use one of the microwavable products for humans,” says Solum. “I probably wouldn’t use an electric heating pad, but there are benefits to using heat along the axial skeleton to give more mobility and prepare the horse to be athletic. Then I’d follow that up with ice after activity.”

Be cautious about the material’s temperature; you can damage tissue if it’s too hot. If you cannot tolerate the heat on your skin, it’s unlikely the horse can.

Be sure to discuss ice and heat therapy with your veterinarian before using them on your horse, because in some situations one is more beneficial (or could be detrimental).

Maintenance Begins with Fitness

Complementary therapies offer diverse options for enhancing performance and well-being. Boldt says collaboration with veterinarians and integration with conventional therapies are key factors in developing a holistic approach to maintaining performance horses.

“Integrative therapies are another tool in the toolbox—another therapy we can use with conventional therapies,” he says. “They can’t be used for everything, and I’m an advocate that they are done by a veterinarian.”

Although it can be argued that conditioning and exercise fall under rehabilitation, our sources here agree they are fundamental. Kaneps explains that people don’t run a 10K or a marathon without proper training. If they do, they are likely to sustain an injury. The same is true in equine athletes.

“Rehabilitation and conditioning exercise are the basis for having a good, strong equine athlete who is capable, and it hopefully helps prevent injury,” he adds. “When we see a horse with a sore back, we may use laser, shock wave, injection, or acupuncture, and the pain may be removed. But ultimately the horse needs to build core strength, topline strength, and flexibility and through exercise to build up that core.”

Selective treatment strategies can combat antimicrobial resistance while protecting foals from R. equi

Rhodococcus equi is a hardy bacterium that lives in the soil and horse feces. It replicates in horse manure, so on densely stocked farms such as breeding operations, the environment can become heavily contaminated. When the bacterium becomes aerosolized—primarily due to environmental factors such as wind, dry conditions, and soil disturbances—foals can inhale it, potentially becoming infected.

Two forms of the bacterium exist: an avirulent form that is essentially benign for foals and another that is a virulent form. The virulent, disease-causing form has a specific genetic element called a plasmid with a gene that codes for a protein called the virulence-associated protein or VapA.

“The VapA protein enables R. equi to replicate inside immune cells in the lungs of foals, alveolar macrophages, leading to abscesses forming in the lung. This disease process is similar to what happens in tuberculosis, where the bacterium known as Mycobacterium tuberculosis is able to replicate in alveolar macrophages of humans to cause pneumonia,” explains Noah Cohen, VMD, MPH, PhD, Dipl. ACVIM, of Texas A&M University’s College of Veterinary Medicine & Biomedical Sciences, in College Station. Cohen is professor of equine internal medicine, Glenn Blodgett Chair in Equine Studies, and associate department head for research and graduate studies in the college’s Department of Large Animal Clinical Sciences.

Foals living on endemic farms are exposed to virulent R. equi from birth and can become infected at a very young age. But most foals don’t exhibit clinical signs of pneumonia until they are 1 to 3 months old or older. Signs in foals resemble what we would see in a child: fever, lethargy, and coughing.

Experts say R. equi pneumonia poses significant challenges for the equine
industry due to a number of different factors, including:

1. The high costs of prevention/treatment;
2. The economic losses associated with foal mortality in severe cases; and
3. The reduced athletic potential of recovered foals as adults.

Further, antimicrobial resistance to medications often used to treat this condition adds to the complexity of managing R. equi.

In this article we’ll review some important facts about diagnosing and treating R. equi pneumonia, address issues related to antimicrobial resistance, and describe the work underway to create a not-so-secret weapon to fight this historically indomitable bacterium: a vaccine.

Fact No. 1: R. equi infection often leads to a self-resolving subclinical (without obvious clinical signs) pneumonia that typically does not need to be treated.

Veterinarians first started using thoracic ultrasonography in 2001 to screen foals for the presence of abscesses within the lungs suggestive of R. equi pneumonia.

“Studies conducted in 2005 and 2008 indicate that thoracic ultrasound screening and treatment of subclinical cases decreased the incidence of pneumonia and decreased the number of hospitalized foals,” says Angela Bordin, MS, PhD, assistant professor in the Department of Large Animal Clinical Sciences at Texas A&M.

This led to the widespread adoption of a screen-and-treat approach, where veterinarians began treating foals with evidence of pulmonary abscesses, even if the foals showed no clinical signs of pneumonia. 

In additional studies researchers discovered the following:

Fact No 2: Thoracic ultrasound exams at farms with endemic R. equi show that often more than 50% of foals are subclinically infected.

Fact No. 3: An estimated 70-85% of subclinically infected foals heal over time without treatment.

“This information led to the realization that not all foals with lung abscesses attributed to R. equi need to be treated,” explains Cohen.

But it was too late.

The Screen-and-Treat Fallout

“Thoracic ultrasound allows us to identify foals that have a lesion/abscess in their lungs before they have clinical disease,” says Bordin. “These lesions can progress to a severe pneumonia. Given there is no vaccine available, and the variability associated with Re-HIP administration (that of R.-equi-specific hyperimmune plasma), it is understandable that thoracic ultrasound seemed an attractive way to detect and treat foals with subclinical pneumonia.”

Avoiding R. equi infection is important because of the economic and welfare implications for farms and their horses.

“But the screen-and-treat strategy came with a price,” she continues. “Antimicrobial resistance in clinical isolates of R. equi from foals was rare before 2001, but it increased significantly after thoracic ultrasound screening. To exemplify, one study documented a higher prevalence of multidrug-resistant R. equi from 2007 to 2017 compared to 1999 to 2006 (Huber, 2018). In another study multidrug-resistant R. equi were isolated from soil samples of 76 out of 100 horse-breeding farms (Huber, 2019).”

Cohen concurs, adding, “As a result of the widespread, unnecessary use of antibiotics in foals without clinical signs of pneumonia, strains of R. equi resistant to the class of antibiotics most effective for treatment of rhodococcal pneumonia in foals began to emerge.”

A Closer Look at Antimicrobial Resistance to R. equi

“Antimicrobial resistance in R. equi is primarily driven by the acquisition of plasmids, which carry resistance genes for multiple antibiotics, including macrolides, aminoglycosides, and tetracyclines,” says Laura Huber, DVM, MSc, PhD, Dipl. ACVPM, assistant professor at the College of Veterinary Medicine, Auburn University, in Alabama. “These plasmids enable horizontal gene transfer between bacteria, allowing R. equi to rapidly acquire and spread resistance within microbial communities.”

Huber explains that the accumulation of antimicrobial residues from past antibiotic use can persist in the environment for many years, creating ongoing selective pressure that helps sustain antimicrobial resistance even after antibiotic use ends. In other words, the lingering antibiotics allow bacteria possessing resistant genes to survive and reproduce while killing off susceptible bacteria, leading to a population dominated by resistant strains over time.

“Our team is investigating the potential impact of antibiotic treatments in foals on the contamination of horse farm soil with antimicrobial residues,” says Huber. “We’re specifically studying how long these residues persist in the soil and how they contribute to the maintenance and spread of antimicrobial resistance, focusing on the long-term environmental effects of antibiotic use in animal care.”

And antimicrobial resistance can spread between different bacteria and species, creating a significant risk to other animals and humans.

“Rhodococcus equi is an ideal model for the One Health concept, as it links human, animal, and environmental health,” explains Huber. “The bacterium can be transmitted from the soil to both animals and humans, illustrating the interconnectedness of environmental, animal, and human health in the spread of infectious diseases and antimicrobial resistance.”

Treat for R. equi When Needed

Despite the bleak picture as far as R. equi antimicrobial resistance, Cohen stresses the importance of recognizing sick foals.

Fact No. 4: Foals diagnosed with R. equi pneumonia should be treated.

“The challenging part for veterinarians is that we do not yet know which foals will self-cure and which will require treatment,” says Cohen.

He and other experts say vets can make an R. equi pneumonia diagnosis based on:

• Farm history of R. equi pneumonia;
• Foals 1 to 6 six months old on the farm;
• The presence of appropriate clinical signs;
• Thoracic ultrasound or X rays showing lung abscesses or consolidation (areas filled with a substance besides air);
• Blood work showing a high white cell count and elevated concentration of inflammation-associated proteins such as fibrinogen or serum amyloid A; and
• Culture and microscopic examination (cytology) of a sterilely collected aspirate from the upper respiratory tract (trachea/bronchioles) to isolate and visualize bacteria and, ideally, identification of the VapA gene by polymerase chain reaction test (PCR).

Fact No. 5: Vets should not rely solely on thoracic ultrasonography to decide which foals to treat.

Further, veterinarians should not rely solely on blood work, such as a complete blood cell count, to diagnose R. equi; it’s better to also have cytologic or PCR evidence.

Fact No. 6: Foals infected with resistant strains of R. equi have a significantly lower survival rate compared to those infected with antimicrobial-susceptible strains.

When treating foals, experts have long recommended using a combination of rifampin and the macrolides azithromycin, clarithromycin, or tulathromycin. When resistance to rifampin exists, veterinarians can use the tetracycline antibiotic doxycycline as a substitute. But are these substitutions as effective as the rifampin/azithromycin combination once was?

“There needs to be more research on that,” Bordin says.

Preventive Strategies: The Elusive Vaccine and Re-HIP Therapy

Fact No. 7: Preventing disease is preferrable to overtreating. The goal of a prevention program is to reduce clinical pneumonia cases, thereby decreasing antimicrobial use and the subsequent development of antimicrobial resistance.

Vaccination

For many infectious diseases, vaccination has proven to be an effective preventive measure, decreasing the incidence and severity of diseases. But R. equi has proven a difficult pathogen for vaccine creation.

Various factors contribute to the challenge of developing a vaccine for R. equi. For example, this is an intracellular pathogen, and we lack a clear understanding of the immunity that protects against it.

“Foals are exposed to R. equi from birth and are most susceptible to infection when they are very young,” Cohen explains. “Their immune systems are naive and immature such that many foals can’t mount effective immune responses. But we know that giving foals the virulent organism in large numbers by stomach tube provides protection against infection, so we know that they can mount protective immune responses within the first few weeks of life.”

In his most recent attempt at creating a vaccine, Cohen, together with his research team, created a messenger RNA (mRNA) vaccine that encodes the VapA protein. After delivery—injection, in this case—the vaccine produces VapA in small amounts, which stimulates the foal’s immune system to mount immune responses to virulent R. equi strains. These immune responses are innate, meaning a general defense that happens immediately, and adaptive, which is a more specific response that occurs later.

“The vaccine did not work very well when delivered via nebulization directly to the lungs,” he notes. “When we gave it intramuscularly, that seemed to stimulate immune responses.”

Cohen says additional studies are needed to further determine if this mRNA vaccine is indeed worth pursuing in foals, or if efforts should return to producing an mRNA (or other) vaccine administered to pregnant mares instead.

“Vaccinating the mares may result in the production of antibodies against VapA that can be transferred to their foals through the colostrum and milk to protect the foal during the highly vulnerable period in the first weeks of life,” says Cohen. 

R. equi-Specific Hyperimmune Plasma (Re-HIP)

Most farms with endemic R. equi rely on Re-HIP for preventing infection in young foals. These plasma products are produced from mares vaccinated against R. equi using a product designed for adult horses. Foals receive Re-HIP intravenously shortly after birth, but the mechanism of action is unclear.

Although the approach was once considered controversial as far as its efficacy, Cohen says, “The bulk of the evidence indicates protective effects of transfusing hyperimmune plasma to foals, but the protective effects are not complete and vary among plasma products, farms, and individual foals. While we need better evidence in the form of well-controlled trials to get clearer evidence, current knowledge indicates that Re-HIP is the best prevention that we have available at this time.”

Fact No. 8: Experts recommend administering 2 liters of Re-HIP that has high activity against VapA to foals within the first day of life.

This conclusion is based largely on studies conducted by Cohen’s team, including a pinnacle study by Susanne Khan in 2019 published in Equine Veterinary Education.

“I think at most endemic farms, it makes sense both medically and financially to transfuse with anti-rhodococcal plasma because there is no effective alternative for controlling R. equi pneumonia,” says Cohen.

However, he notes that the advantages of Re-HIP are not as apparent on nonendemic horse farms.

“The decision as to whether to use Re-HIP needs to be made by the farm veterinarian, farm manager, and owners of the foals to assess both the risk of the disease and their levels of risk aversion,” Cohen says. “At nonendemic farms it is less clear whether costs and risks of Re-HIP outweigh the potential benefits of preventing something that may not be present.”

Future Directions in R. equi Research

Veterinarians gained valuable insights into R. equi through routine treatment following thoracic ultrasound screening in the early 2000s (based on the work of Steeve Giguère, DVM, PhD, Dipl. ACVIM, and others). However, our sources say much more research is necessary to get ahead of this economically draining disease. Specifically, vets need effective and efficient preventive strategies, ideally in the form of a vaccine, to prevent neonatal morbidity and mortality. 

“Because of limited availability of research funding, it will take years for researchers to test their ideas surrounding mare and foal vaccines,” says Cohen. “But we are nothing if not persistent and will continue to work hard to try to investigate an approach to protect foals.”

On the antibiotic-resistance front, Huber adds, “Responsible antibiotic use can slow the spread of antimicrobial resistance.”

She says veterinarians should use ultrasound to detect R. equi early and institute more targeted management, rather than relying on the screen-and-treat program. This approach would help reduce unnecessary antibiotic use. “Developing clear guidelines that combine ultrasound findings with clinical signs is crucial to avoid overuse of antimicrobials and ensuring that antibiotics are only administered when truly necessary,” says Huber. “While these approaches can help manage antimicrobial resistance, fully reversing the damage will require broader strategies, including improved (antimicrobial) stewardship and environmental control.”

This article is from the Spring 2025 issue of The Horse: Your Guide to Equine Health Care. We at The Horse work to provide you with the latest and most reliable news and information on equine health, care, management, and welfare through our magazine and TheHorse.com. Your subscription helps The Horse continue to offer this vital resource to horse owners of all breeds, disciplines, and experience levels. To access current issues included in your subscription, please sign in to the Apple or Google apps OR click here for the desktop version.

Slow, progressive exercises help improve a horse’s strength and stability when recovering from this neurologic disease

Equine protozoal myeloencephalopathy (EPM) is a neurologic disease caused by the protozoa Sarcocystis neurona or Neospora hughesi and can lead to deficits including ataxia (incoordination), gait abnormalities, and muscle weakness or atrophy.

S. neurona is typically found in the Western Hemisphere, and the definitive host is the opossum. Opossums can get it by scavenging on infected cats, raccoons, and other intermediate hosts. Horses become infected by ingesting feed or water contaminated with opossum droppings. N. hughesi rarely causes EPM in horses, but sporadic cases arise from this organism. Researchers do not yet know what natural hosts can transmit N. hughesi.

Risk Factors for EPM

Researchers estimate 15-90% of horses have been exposed to S. neurona and, therefore, have antibodies in their bloodstream. However, exposure does not always lead to infection—the annual incidence of EPM is less than 1% in the United States. Horses diagnosed with EPM infection are often younger than 4 or older than 13 years old.

Veterinarians see the highest number of EPM cases during the fall, while the disease is much less common during the winter months. Stress, including immune system compromise, intense exercise, transportation, injury, surgery, or foaling can increase a horse’s chances of developing clinical (apparent) EPM.

Diagnosing EPM in Horses

When a horse exhibits clinical signs of EPM, veterinarians must distinguish the disease from lameness or other neurologic conditions such as cervical vertebral stenotic myelopathy (wobbler syndrome), equine
herpesvirus-1 myeloencephalopathy (EHM), rabies, and Lyme disease. Currently, the only definitive way for veterinarians to diagnose EPM is by identifying parasites in the brain or spinal cord during a necropsy.

Veterinarians typically diagnose EPM in horses by conducting SAG2, 4/3 ELISA testing, which is performed on serum and cerebrospinal fluid (CSF). They compare the antibody levels in the bloodstream to those in the CSF to see if CSF antibody levels are higher than expected compared to normal diffusion of antibodies from the blood. This would indicate antibody production in the central nervous system. Some practitioners might take cervical radiographs to check for spinal changes that appear more significant than expected with normal aging and could indicate another pathology as the cause of neurologic deficits.

Treating EPM in Horses

Veterinarians have several FDA-approved drugs available to treat horses with EPM: triazines and folate-inhibiting drugs. They also often recommend supplementing with vitamin E.

Researchers have suggested the triazines diclazuril and ponazuril both target the apicoplast organelle in S. neurona, which mammal cells do not contain.

Sulfadiazine and pyrimethamine are folate-inhibiting drugs used in combination to block folate synthesis in S. neurona, which it needs for survival. Researchers have reported vitamin E’s antioxidant properties can help protect the damaged central nervous system from oxidant injury.

With FDA-approved treatment, 57-62% of horses show improvement in clinical signs, but about 10% of horses relapse within one to three years of treatment.

Preventing EPM in Horses

Limiting opossum access to your horse’s feed and water sources remains one of the best ways to lower his risk of S. neurona or N. hughesi infection. Decreasing his stress levels and improving his overall health can also positively impact immune function, possibly lowering his risk of protozoal infection. In some situations your veterinarian might recommend intermittent treatment with low doses of diclazuril to reduce infections.

A Challenging EPM Case

In September 2020 veterinarians  at the University of Georgia’s School of Veterinary Medicine, in Athens, admitted George, a then-15-year-old Warmblood gelding used for dressage presenting with moderate neurologic deficits. A few days into his hospital stay, Katie Ellis, DVM, MS, Dipl. ACVSMR, clinical assistant professor, was brought onto the team.

In his case report George’s clinicians described him as bright, alert, and responsive on admission to the hospital. He was very ataxic in the hind limbs as he walked off the trailer and while being turned around in his stall, and in the hospital he dog-sat (a common sign of ataxia).

They also observed that George’s neurologic deficits were more pronounced in the hind limbs, especially on the right, than in the forelimbs. When his vets observed him on tight circles to both the right and left, they reported more significant gait deficits.

George’s clinicians performed cervical radiographs and SAG2, 4/3 ELISA testing to confirm their suspicions of EPM. The cervical radiographs showed only mild changes consistent with his age and work. His CSF analysis revealed high protein levels, which the veterinarians noted can be consistent with EPM infection, and serum titers confirmed their diagnosis.

Treatment and Rehabilitation

George’s veterinarians treated him with ponazuril along with sulfadiazine and pyrimethamine. “These drugs act by two different mechanisms to kill the protozoa and thus stop the parasite from inflicting further damage to the central nervous system,” they wrote in his report. “The gelding’s response to treatment has been positive, and his neurologic clinical signs have continued to improve since starting medication.”

In addition to medical treatment, Ellis and her team developed and completed daily rehabilitation exercises with George to help strengthen his muscles and improve his overall coordination. (See sidebar on page 33.)

Veterinarians employ physiotherapy as one of the first rehabilitation techniques for a neurologic horse, Ellis says.

Once George was stable standing on flat ground and able to pick up all four feet, Ellis used proprioceptive balance pads as the next step in improving his coordination and balance. “The horse should start with firm pads and only the front or hind feet on pads before moving to softer pads or placing all four feet on at the same time,” she says. Because this exercise can be very physically challenging for horses, she says she only incorporated it for short periods of time and increased the difficulty slowly based on George’s progress.

After George was stable hand-walking in a straight line, Ellis and her team started incorporating walking him in a serpentine pattern and over surface changes (i.e., from pavement to grass or arena footing).

George’s Future

University clinicians discharged George from the hospital after he underwent 28 days of treatment and rehabilitation. His owner continued his rehabilitation with guidance from and regular check-ins with Ellis. At his last recheck in 2021, George had progressed to light ridden exercise and was continuously improving.

Editor’s note: To protect the horse’s anonymity, we have changed his name in this article.

This article is from the Spring 2025 issue of The Horse: Your Guide to Equine Health Care. We at The Horse work to provide you with the latest and most reliable news and information on equine health, care, management, and welfare through our magazine and TheHorse.com. Your subscription helps The Horse continue to offer this vital resource to horse owners of all breeds, disciplines, and experience levels. To access current issues included in your subscription, please sign in to the Apple or Google apps OR click here for the desktop version.

Dysphagia, or difficulty swallowing, can have serious consequences for foals. At the 2025 Cavalcade Education Equine Reproduction Seminar, held on Jan. 8, in Red Hook, New York, Lauren Holley, BVSc (Hons), Dipl. ACVIM, of Rhinebeck Equine, also in New York, explained the importance of diagnosing dysphagia in foals early and properly managing them to prevent respiratory dysfunction and aspiration pneumonia.

Critical First Steps: Assessing the Newborn Foal

Holley highlighted the importance of a neonatal physical exam at birth to catch dysphagia and other potential abnormalities early. With this hands-on physical exam, the veterinarian should evaluate:

• Vital signs;
• Heart sounds;
• Limb deformities;
• The umbilicus; and
• The respiratory system.

Signs of Respiratory Dysfunction in Foals

Aside from milk coming out of the nostrils—considered a definite sign of disease—other clinical signs of dysphagia in the foal include:

• Nasal discharge;
• Abnormal respiratory rate and effort; and
• Respiratory noises, such as stridor (abnormal sounds heard when inhaling).

“The most concerning clinical sign remains milk coming out of the nostrils, which requires immediate veterinary attention,” Holley said. “If this is observed, the foal should be muzzled and separated from the mare while waiting for the vet, as continued nursing increases the risk of aspiration pneumonia from milk pooling in the lungs.”

Causes of Dysphagia in Foals

Dysphagia usually stems from two primary issues: one functional, the other structural.Functional dysphagia occurs relatively frequently and often appears in cases involving prematurity, neonatal encephalopathy (also called “dummy foal” syndrome), or systemic illness. Structural issues, though less frequent, include cleft palates, cysts, and esophageal dysfunction.

Diagnosing Dysphagia in Foals

If practitioners suspect dysphagia in foals, they might perform blood tests to assess systemic inflammation and organ function and pursue diagnostic imaging in the form of ultrasonography, radiography, or endoscopy. “Endoscopy is considered the most important diagnostic tool as it allows us to directly visualize the upper airway and trachea for evidence of aspiration or structural abnormalities,” said Holley. Endoscopic videos can reveal weak or collapsed pharyngeal muscles, inflammation, and the presence of milk in the trachea.

Treating Dysphagia

Holley said the goals when treating dysphagia in newborn foals include three main objectives: Stop aspiration, reduce inflammation, and address secondary bacterial pneumonia. Veterinarians might treat foals that have dysphagia by placing a nasogastric feeding tube and administering anti-inflammatory medications and broad-spectrum antibiotics. In select cases veterinarians recommend antioxidants—notably vitamin E and selenium—to address nutritional deficiencies that negatively affect foals’ neuromuscular function.

Foals with severe structural abnormalities or neurologic issues might need longer-term management, such as bucket feeding rather than nursing until weaning. Veterinarians often perform repeat endoscopic evaluations on these foals to monitor their progress and guide treatment.

Take-Home Message

Dysphagia in newborn foals can be serious, but it often improves with early diagnosis and treatment. Most foals recover well, especially when the cause is functional—those cases usually resolve within five days. Because complications such as aspiration pneumonia can develop quickly, horse owners and veterinarians must act promptly, identifying the cause of dysphagia and implementing appropriate supportive care to give these foals the best chance at a full recovery.

Postpartum mares face a higher risk of developing large colon volvulus—a life-threatening type of colic in which the colon twists 360 degrees or more, cutting off blood flow and blocking the passage of gas and feed. Jesse Tyma, DVM, Dip. ACVS, a surgeon at Rhinebeck Equine, in New York, described the diagnostic and treatment approaches to this condition at the 2025 Cavalcade Education Equine Reproduction Seminar, held in Red Hook, New York, on Jan. 8.

Anatomy and Susceptibility in Postpartum Mares

Tyma described the large colon as a partially mobile gastrointestinal organ prone to displacement and twisting within the horse’s abdomen. The reason postpartum mares are especially susceptible to this condition relates to the empty space left in the abdomen after foaling, which allows the colon to shift more easily.

Diagnosing Large Colon Volvulus in Mares

The clinical signs of colic in a mare with large colon volvulus are usually severe, including vigorous pawing, violent rolling, a bloated appearance, and intractable discomfort. Tyma emphasized that prompt diagnosis and treatment are critical to the mare’s survival and foal’s safety.

“The colic exam aims to assess the postpartum mare’s overall health status, localize the lesion, and differentiate between a volvulus involving ischemia (lack of blood flow leading to oxygen deprivation and tissue death) and a displacement or other type of colic where the blood supply is unaffected,” said Tyma. “Diagnostics may include palpation per rectum, passing a nasogastric tube to check for gastric reflux, abdominal ultrasound to evaluate the colon wall and vasculature positioning, and bloodwork to measure lactate levels (which can signal severe tissue damage and the need for urgent intervention) and assess overall systemic health.”

Tyma also stressed the need to carefully assess the reproductive tract in the immediate postpartum colicky mare to rule out life-threatening hemorrhage, the clinical signs of which can overlap with those of large colon volvulus.

Treating Large Colon Volvulus in Mares

If a veterinarian strongly suspects large colon volvulus, the mare will likely need emergency colic surgery. “The goals of surgery are to characterize the lesion, manually correct the volvulus, and assess bowel viability to guide surgery decisions,” said Tyma. The surgeon might also perform a colon resection (the damaged tissue can be removed, and the healthy ends of the intestine stitched back together) or colopexy (creating an adhesion to the body wall to prevent future displacements and torsions), she added.

Postoperative Care and Complications

Beyond the risks of surgery and general anesthesia, recovery from large colon volvulus surgery involves intensive care because these mares often become systemically compromised and can decline quickly. “The postoperative patient requires close monitoring with serial examinations, multimodal pain management, fluid therapy, broad-spectrum antimicrobials, digital cryotherapy (icing the legs), supportive care, and a gradual reintroduction of feed,” Tyma said.

She added that common postoperative complications can include endotoxemia (toxin release into the bloodstream), diarrhea, recurrent colic, surgical site infection, and the painful hoof condition laminitis. “Transitioning the accompanying foal to a nurse mare is often recommended to lessen the physiologic demand on mares early in the postpartum period.”

Prognosis for Large Colon Volvulus in Mares

“In the best of clinical scenarios, the short-term prognosis for large colon volvulus is excellent, with survival rates reported up to 90%,” Tyma said. “However, in studies representing a broad population with variable referral access (to a surgical facility), the short-term survival rate is just 71%, with long term survival dropping to less than 50% by one year postoperatively. This speaks to the importance of quick referral and management for successful outcomes.”

Sixty-seven percent of mares treated for large colon volvulus produce at least one foal postoperatively. “The risk of recurrence of large colon malposition (inclusive of both surgical correction of displacement and volvulus) is 15%, and, following two occurrences of volvulus, the recurrence rate jumps to 80%, which is significant,” Tyma said. “Mares with recurrent volvulus that are intended to continue as broodmares should be considered candidates for a prophylactic procedure (colopexy or large colon resection) to reduce the risk of recurrence.”

Take-Home Message

Large colon volvulus presents a true emergency in postpartum mares, demanding rapid diagnosis, aggressive treatment, and intensive postoperative care. Tyma emphasized the importance of prompt referral to a surgical facility and potentially prophylactic procedures such as colon resection or colopexy in high-risk mares to reduce the risk of recurrence. “Prognoses for survival and continuation of reproductive careers can be good to excellent but remain dependent upon quick recognition of the condition, immediate action, and appropriate surgical and postoperative management,” she said.

Why is it so difficult for equine veterinarians to change prescribing practices? That’s the question Clare Ryan, DVM, PhD, Dipl. ACVIM-LA, from the Department of Infectious Diseases, at the University of Georgia’s College of Veterinary Medicine, in Athens, posed during her presentation at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11 in Orlando, Florida. One reason, she said, is that changing behavior is challenging.

“Things always come up that keep us from making changes that we know are important … we are busy!” she said. “And with push back from clients when we try to change our behavior, it can be even more difficult, especially when trying to step away from the higher-tier antibiotics toward first-tier antibiotics.”

Ryan used ceftiofur as an example: “It’s a fantastic drug,” she said. “A third-­generation cephalosporin with activity against both Gram-positive and -­negative microbes approved for Streptococcus equi respiratory infections and, of course, effective for many off-label conditions. It is widely available, affordable, convenient to administer, especially if needed long-term, and usually has few adverse effects.”

A big downside, Ryan said, is the significant impact cephalosporin resistance has on treating serious infections in humans. The potential impact is so big, the World Health Organization classifies ceftiofur as an HPCIA (highest-priority critically important antimicrobial), meaning it should be used sparingly in equine practice.

“The University of Georgia has an antimicrobial stewardship committee to help guide prescribing practices for hospital veterinarians, and they have a tier system,” Ryan explained. “In this system, ceftiofur is tier 2, not first-line therapy.”

When is it appropriate to use ceftiofur? Ryan described a litmus test to find out:

1. Is ceftiofur effective at treating the bacteria causing the infection? Enterococci, Pseudomonas, and Salmonella are inherently resistant to cephalosporins.
2. Is the cultured organism’s minimum inhibitory concentration (MIC) above the reported MIC break point?
3. Can ceftiofur reach adequate concentrations at the infection site? It cannot in the meninges, placenta, or joints.
4. Are reasonable alternatives available, such as beta lactams (penicillin, ampicillin), sulfas, tetracyclines, or gentamycin, that are not HPCIAs?

For which clinical conditions is ceftiofur use appropriate? Ryan explained the Gram-positive respiratory infections it is labeled for (at times combined with an aminoglycoside for Gram-negative coverage), urinary tract infections, and potentially some cases of endometritis with Gram-­positive organisms.

“If treating foal bronchopneumonia, fresh wounds/lacerations, following choke, for surgical prophylaxis, or strangles, we really should be looking for the lower-tiered drugs,” she said.

Further, she emphasized that we should reach for nonantibiotic therapies and employ vaccination, improved husbandry, and biosecurity protocols to prevent disease.

How can you start making changes in your antibiotic-prescribing habits?

“Be curious about antimicrobial stewardship,” said Ryan. “Start by picking small things and implement one at a time. Don’t think you’re going to suddenly be a perfect antimicrobial steward in one afternoon.”

Also, find a like-minded colleague and develop your own antimicrobial use guidelines, holding each other accountable and leading the way for other practitioners to follow suit.

Mats Troedsson, DVM, PhD, Dipl. ACT, DECAR, of the University of Kentucky’s Maxwell H. Gluck Equine Research Center, in Lexington, Kentucky, addressed antimicrobial resistance (AMR) from a reproduction standpoint during a presentation at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida. 

In theriogenology, veterinarians use antibiotics to not only treat infections but also improve reproductive efficiency in the absence of illness. They often administer antibiotics in post­breeding intrauterine infusions, following natural mating, during embryo transfer, and in semen extenders for artificial insemination without evidence of infection. 

Breeding-induced or physiologic endometritis (inflammation of the endometrium, or uterine lining) is predominately triggered by the presence of sperm, not bacteria, in the uterus. The purpose of this inflammatory reaction is to eliminate excess sperm and any contaminating bacteria and inflammatory products to allow a hospitable environment for the embryo.  

Recent data show, however, that almost 30% of mares clear the uterus of inflammation within six hours of breeding/insemination/embryo transfer, and approximately 85% of broodmares are resistant to persistent endometritis. 

“This emphasizes how effective the uterine defense mechanism is,” said Troedsson. 

For mares that can’t clear the inflammation, we need to ask why, he said. 

“We have previously shown that these mares have impaired myometrial contractility in response to inflammation due to accumulation of nitric oxide in the uterus as well as an imbalance between pro- and anti-inflammatory cytokines in response to breeding,” said Troedsson. “Predisposing factors can also include poor perineal conformation.” 

When a mare fails to clear bacteria from the uterus, antibiotics are indicated and should be selected based on culture and sensitivity results. Treatment should continue for three to five days and can be combined with uterine lavage if fluid is present. Note that mares diagnosed with bacterial endometritis will not be bred in the same cycle, so there is time to wait for the laboratory results to guide treatment, he said. 

In the case of treatment failures, consider the presence of resistant or dormant bacteria located in the deeper layers of the endometrium or endometrial glands or the presence of biofilm. 

“bActivate is a sterile growth medium that activates dormant Streptococcus zooepidemicus after being instilled in the uterus,” said Troedsson. “The uterus can be cultured the day after activation and the mare treated if the culture is positive. If the culture is negative, the uterus is clear.” This also works for other bacteria, he noted. 

In the case of persistent infectious endometritis that doesn’t respond to treatment, biofilms that evade both the immune system and antibiotics could be to blame.  

“Bacteria on the surface of the biofilm are exposed to sufficient concentrations of antibiotics, but reduced diffusion through the biofilm matrix leads to decreased concentration of antimicrobials within the biofilm community,” he explained. “This provides an excellent opportunity for bacteria to develop AMR. Further, genetic alterations associated with AMR are easily transmitted between bacteria in the biofilm, contributing to AMR.” 

To treat these infections, vets must first diagnose or suspect a biofilm, then break it down. “Biofilms are very difficult to diagnose in the field,” Troedsson said. “One potential way of diagnosing biofilms is to identify proteins or lipids specific to biofilms. If those molecules can be consistently recovered from mares with biofilms, an in vivo assay can be developed.” 

While veterinarians must treat endometritis using antibiotic therapy, Troedsson ­recommends treating breeding-induced endometritis with ecbolics, lavage, and possibly immune modulators, such as bacterial cell wall fractions (Settle), platelet-rich plasma, dexamethasone, or lactoferrin. 

“Antibiotics are not the first choice,” he stressed. “We know it is semen, not bacteria, causing the inflammation and subsequent uterine fluid.” 

Troedsson concluded by stating that while antimicrobials are valuable in equine reproduction for proven infections, using antibiotics to assist reproductive efficiency in horses with no health and well-being issues poses a challenge to equine practitioners. 

“We need alternatives to antibiotics, and decisions should be made based on scientific data rather than traditions and habits, such as routinely using antibiotics to flush mares 24 hours post-mating,” he said. 

A key strategy for reducing antibiotic use in equine practice is to limit prophylactic administration and only treat horses with evidence of infection. 

“Every time we prescribe an antibiotic, we are creating a potential risk of resistance, both the pathogen causing the disease and the natural flora of the patient,” said Pamela Velarde, DVM, a resident in large animal medicine at Cornell University College of Veterinary Medicine’s Department of Clinical Sciences, in Ithaca, New York. “Minimizing the use of the World Health Organization’s list of high-priority and critically important antimicrobials (HPCIAs and CIAs) in our veterinary patients is imperative, and antibiotics in general should only be prescribed when infection is documented and clinically significant.” 

Velarde and colleague Gillian Perkins, DVM, Dipl. ACVIM, recently completed a retrospective study of antimicrobial prescribing practices at Cornell’s Veterinary Teaching Hospital to identify areas of possible improvement. They presented their findings at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida. 

In 2021 about one-third of equine patients seen at the hospital were prescribed systemic antimicrobials—including a small percentage of HPCIAs—to treat infections affecting the musculoskeletal, upper respiratory, reproductive, gastrointestinal, and other systems. 

“Out of the 543 horses prescribed an antibiotic, no evidence of infection existed in almost half of the horses,” said Velarde. “Only a small percentage (< 15%) of the horses prescribed an antibiotic had confirmed infections based on culture.” 

For horses undergoing surgery, all were treated with antibiotics, including many horses that had what were considered “clean” surgeries (i.e., elective procedures performed on clean, nontraumatic, and noninflamed surgical sites that didn’t involve opening up the abdomen). 

“Key findings of our data were that approximately a third of the horses were prescribed antibiotics, and culture and sensitivity were only infrequently done,” she said. “Overall, limited prescriptions included HPCIAs. These data suggest that we can do a better job of antimicrobial stewardship for cases with no evidence of infection and for clean surgeries. We need to continue to critically evaluate if horses in these scenarios should be prescribed antimicrobials at all.” 

The next phase of this study is to establish antimicrobial stewardship guidelines for the hospital using a three-tiered approach following WHO guidelines on medically important antimicrobials: increasing justification for use, need for culture and sensitivity, and approval by the Infection Control Committee. 

Degenerative suspensory ligament desmitis (DSLD) is a complex, progressive condition that causes pain and lameness in horses. Though researchers currently consider DSLD to be uncurable, they are working to better understand the degenerative changes that occur in the suspensory ligament and identify genes potentially involved in the development of DSLD. In this excerpt from Ask TheHorse Live, Katie Ellis, DVM, MS, Dipl. ACVSMR, of the University of Georgia, answers a reader’s question about how she can reduce her horse’s joint pain if he also has DSLD. 

This podcast is an excerpt of our Ask TheHorse Live Q&A, “What You Need to Know About Equine Degenerative Joint Disease.” Listen to the full recording here.

About the Expert

Katie Ellis, DVM, MS, Dipl. ACVSMR

Katie Ellis, DVM, MS, Dipl. ACVSMR, is a clinical assistant professor and section head of field services at the University of Georgia’s College of Veterinary Medicine, in Athens. Her research interests include equine rehabilitation and musculoskeletal imaging.

During a presentation devoted to responsible antimicrobial use and selection at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11 in Orlando, Florida, Lucas Pantaleon, DVM, MS, Dipl. ACVIM, MBA, a veterinarian advisor at DVM One Health, in Versailles, Kentucky, referred to antimicrobial resistance (AMR) as a “silent pandemic” that we must address with a One Health framework approach.

“Antimicrobial-resistant bacteria can develop, disseminate, and have impacts on human, animal, and environmental health, incurring a huge economic burden,” he said.  

Pantaleon said we will never be able to completely defeat AMR because bacteria have an innate capacity to acquire resistance to drugs that were once effective. Instead, he urged veterinarians to be judicious with their use of antimicrobials to delay the onset of AMR and preserve the drugs we have today.

Pantaleon shared data from a systematic review published in the journal Lancet in 2022 stating that in 2019 there were 1.3 million human deaths attributed to AMR infection and almost 5 million deaths associated with AMR globally. Researchers on a study by the Centers for Disease Control (CDC) relayed that about 3 million people per year are affected by AMR infections, and an estimated 35,000 deaths annually are due to multidrug-resistant bacterial infections. If ignored, by 2050 AMR could cause 10 million deaths globally, with a $100 trillion price tag.

“Today, in the U.S., equine practitioners have the freedom and great responsibility to use any antibiotic to treat patients, because there is no regulatory body guiding antibiotic use in this sector,” he said. “AMR is a wicked problem where the solution requires a large number of people to change their behaviors.”

Pantaleon recommended including behavioral sciences and communication experts to transmit messages regarding AMR to the public.

Even using a One Health approach working across all disciplines in animal, human, and environmental health, Pantaleon warned equine practitioners, “We have monumental challenges ahead of us.”

In equine practice, he said, we must better address how to keep animals healthy, so we don’t need to use antibiotics in the first place. We need better, faster, and ­economical stallside diagnostic testing; improved biosecurity and infection prevention; and regulatory framework to guide us on how to be better with our drugs.

“Antibiotic use must not be a ‘cover-up’ for poor management or suboptimal infection prevention practices,” Pantaleon stressed.

For example, should veterinarians be using an aminoglycoside with every joint injection given the low risk of intra­articular infection? Do we need to infuse every mare post-breeding with antibiotics? Pantaleon said equine vets have many opportunities to improve antibiotic use.

In closing, Pantaleon acknowledge that equine veterinarians have many opportunities to improve our use of antibiotics to combat antimicrobial resistance.

Typically, veterinarians use a thorough physical and lameness examination to localize pain to one area of the horse’s body. Then they use diagnostic imaging to find the pathology that’s causing pain. In this excerpt from Ask TheHorse Live, Katie Ellis, DVM, MS, Dipl. ACVSMR, of the University of Georgia, in Athens, and Howland Mansfield, DVM, CVA, CVMMP, of American Regent Animal Health, describe the common imaging modalities used to diagnose joint disease in horses. 

This podcast is an excerpt of our Ask TheHorse Live Q&A, “What You Need to Know About Equine Degenerative Joint Disease.” Listen to the full recording here.

About the Experts

Katie Ellis, DVM, MS, Dipl. ACVSMR

Katie Ellis, DVM, MS, Dipl. ACVSMR, is a clinical assistant professor and section head of field services at the University of Georgia’s College of Veterinary Medicine, in Athens. Her research interests include equine rehabilitation and musculoskeletal imaging.

Howland M. Mansfield, DVM, CVA, CVMMP

Howland M. Mansfield, DVM, CVA, CVMMP, of Summerville, South Carolina, received her DVM from Tuskegee University School of Veterinary Medicine, in Alabama, and completed internships in both general equine medicine and surgery and in advanced equine reproduction. She is certified in both veterinary acupuncture and veterinary medical manipulation. She has practiced along the East Coast over the course of 14 years, in addition to time in Germany providing veterinary care for some of the most elite show horses in Europe. In 2012 Mansfield was named by the South Carolina Horseman’s Council as the Horse Person of the Year for her efforts in equine rescue and in combating animal cruelty. She joined American Regent in 2023 as a technical services veterinarian where she can support the welfare of and improve health care for horses and small animals throughout the U.S.

Equine orthobiologics broadly defines an array of innovative medical therapies that can help a horse’s body repair, replace, restore, and regenerate cells and tissues that have been damaged by injuries and conditions such as osteoarthritis. In this excerpt from Ask TheHorse Live, Katie Ellis, DVM, MS, Dipl. ACVSMR, of the University of Georgia, in Athens, describes the pros and cons of using orthobiologics to manage joint disease in horses. 

This podcast is an excerpt of our Ask TheHorse Live Q&A, “What You Need to Know About Equine Degenerative Joint Disease.” Listen to the full recording here.

About the Experts

Katie Ellis, DVM, MS, Dipl. ACVSMR

Katie Ellis, DVM, MS, Dipl. ACVSMR, is a clinical assistant professor and section head of field services at the University of Georgia’s College of Veterinary Medicine, in Athens. Her research interests include equine rehabilitation and musculoskeletal imaging.

Ultrasonography has become one of the most versatile field imaging modalities for evaluating equine musculoskeletal injuries because it allows veterinarians to visualize almost any body tissue, most importantly soft tissues such as tendons and ligaments.

Ultrasound uses high-frequency sound waves to produce images in real time. The user holds a sound-wave-emitting probe against the skin toward the structure being evaluated. When the waves meet structures or interfaces between structures, they reflect back to the probe like a ship’s sonar. The more abrupt the interface or dense the structure, the more waves reflected. The more sound waves received, the brighter the structure looks on-screen. We describe brightness in terms of echogenicity. For example, bone appears bright (echogenic), normal fluid is dark (nonechogenic), and all other structures show up somewhere between.

With regard to lameness issues, your veterinarian is most likely to use ultrasound to assess tendons and ligaments, bone surfaces, synovial fluid, and cartilage. Think of tendons and ligaments as ropes made up of many strands or fibers. Tendons connect muscles to bones, while ligaments connect bones. When tendons or ligaments are strained, their fibers might tear. Veterinarians assess the extent of tendon or ligament damage by evaluating its size, echogenicity, and fiber pattern. Often, minor tendon or ligament injuries result in an increase in size, or cross-sectional area. In cases of significant disruption, veterinarians might notice changes in echogenicity and fiber pattern.

Normally, the “echotexture” or patterning of a tendon or ligament is homogenous (the same throughout); a perpendicular view of a normal tendon shows a round or ovoid structure with uniform shading. A damaged tendon might appear round and bright (normal fibers) with a dark area within it. Dark regions represent fiber disruption, or voids, where no sounds waves reflect. Larger, centrally located regions of fiber disruption are commonly referred to as core lesions.

Viewing this same region’s longitudinal axis, with the probe along the length of the tendon or ligament, the normally long, linear fibers might appear short and choppy or be missing altogether. Abnormalities are not always as overt, and true injuries could be as subtle as small, dark linear striations or mildly abnormal edges.

Ultrasound waves cannot penetrate bone, but veterinarians can use them to evaluate its surface. Due to bone’s density, it should look like a bright, white, smooth line on the screen. Bone surface changes at tendon or ligament insertion sites or around arthritic joints, fractures, or osteochondritis dissecans (OCD) lesions cause these lines to look disjointed and/or rough.

Evaluating characteristics within synovial structures (joints, tendon sheaths, and bursas) can be similarly useful. Normal structures have linings that produce a small amount of lubricating, nutrient-rich fluid. With inflammation from tendonitis, arthritis, direct trauma, or any other type of irritation, the lining produces excessive, poor-quality, and sometimes cell- and protein-rich fluid. Evaluating synovial fluid and lining can provide insight into inflammation severity. Additionally, veterinarians can examine joint cartilage for defects caused by traumatic injury or OCD.

Almost as important as making a diagnosis with ultrasound is treating and monitoring injuries with it. For tendon or ligament tears, for instance, veterinarians can administer regenerative products such as stem cells or platelet-rich plasma directly into the region of fiber disruption under ultrasound guidance. They insert a needle in the ultrasound beam so they can visualize penetration depth and see the therapeutic as it enters the space. Veterinarians can treat other areas, such as the sacroiliac, thoracolumbar and cervical facet joints of the spine, with anti-­inflammatory agents via ultrasound guidance, without which they’d be doing it blindly and potentially too distant from the pain site to be effective. Ultrasound guidance also ensures the needle doesn’t inadvertently penetrate other structures.

After injury or treatment, veterinarians perform follow-up clinical and ultrasound exams to assess healing. They look for decreases in cross-sectional area, increases in echogenicity, and improvements in fiber alignment in tendon and ligament injuries. Ultrasonographic improvement and clinical improvement together guide recommendations to increase the horse’s workload.

The portability, versatility, and accuracy of today’s machines make ultrasound an incredibly useful tool. With it vets can image any tissue to determine diagnosis, while helping owners save money and time. It can also help guide placement of therapeutic agents and allow monitoring of recovery. If your practitioner suggests using ultrasound on your horse, knowing its uses, mechanics, and limitations can help provide clarity during the process.

How to prevent shoe loss caused by farrier error, rider issues, management style, or horseplay

The environmental conditions might be wet, dry, slick, or muddy. The horse might be working, playing, stomping, or standing. Under any circumstance, a loose or lost horseshoe can be an inconvenient nuisance. Steve Kraus, CJF, a professional farrier of 55 years and head of farrier services at Cornell University Equine and Farm Animal Hospital, in Ithaca, New York, says horseshoe loss typically has one of three causes:

1. Farrier error.
2. Rider or management issues.
3. The horse.

A clear understanding of how or why a shoe came off is the key to keeping future shoes on your horses’ feet.

Farrier Error

When a horse loses a shoe, some owners might instinctively blame the farrier for subpar work, says Eric Wilt, a professional farrier of more than 30 years and the farrier science manager at Hocking College, in Southeast Ohio. In certain instances they’re right. Kraus and Wilt explain that a multitude of farrier errors can cause shoe loss, including:

• Performing a poor trim job prior to nailing on the shoe.
• Also in that vein, fitting the shoe to the wings (the flares on the horse’s feet that should be removed before placing the shoe), causing the hoof to work unevenly and, thus, loosening the nails.
• Placing a shoe that is too large for the foot such that the horse can easily step on it and rip it off.
• Driving nails too low into the hoof wall to hold the shoe on securely.
• Fitting the shoe too tightly, resulting in the hoof wall spreading over the shoe and the nails shearing.

Any shod horse’s shoe will loosen over time. Horses move, and hooves grow, expand, and contract. These factors come into play in determining a shoe’s life span on the hoof. Wilt says when he is getting ready to shoe a horse, he considers hoof health and conformation as well as the horse’s way of going.

Tips to Reduce Farrier Error

Aside from skill, experience, and a good eye for balance, being able to shoe horses properly with little to no error requires a few basic elements to help the farrier work more efficiently, says Wilt:

• A competent handler or a horse that ties well.
• Good lighting so the farrier can see the entire hoof.
• Level ground to work on so the farrier can properly evaluate horse stance and hoof placement.
• Clean hooves to ensure proper hoof balance and shoe placement.

Rider or Management Issues

A horse’s job, where he spends most of his time, and what he does daily play huge roles in potential shoe loss. When evaluating rider issues causing shoe loss, Kraus points out three issues he sees:

1. Riders that work horses excessively on the forehand, causing them to become unbalanced. The horse’s front feet cannot get out of the way of the hind, and he steps on a front shoe with the hind foot.
2. Riders that move the horse forward, then check the horse abruptly, resulting in the same.
3. Riders that turn the horse at a canter on the wrong lead, so he steps on the outside heel of the front shoe with a hind foot.

Kraus estimates 80-90% of shoe loss due to rider error consists of front shoes being stepped on by hind feet.

Even drivers can cause shoe loss in harness racing, says Wilt. On the racetrack, the driver might have to keep the horse “doubled up” (maintaining a strong pull on the lines to keep the horse from pacing or trotting too fast). Because racing Standardbreds must move at an extended gait, this restraint will not allow the horse to extend his forelimb stride. So, a hind foot might grab a shoe off the diagonal front foot. This can also occur when going slow or jogging on the track, because the horse might switch from a trot to a pace and the hind foot might grab a shoe off the opposite front foot.

Kraus and Wilt say working a horse in any discipline when he is sore or not properly conditioned for the job can result in fatigue, sloppy movement, and interference resulting in a pulled shoe.

Management issues that can cause horseshoe loss are vast. Frederick Wright, a graduate of Cornell University’s Farrier School, has been a practicing professional farrier in the Hartford, Connecticut, area for about five years. He says there is definitely a season for lost shoes, with wet, muddy ground being the worst. Exposure to excessive wet and muddy conditions allows the hoof to become soft and, therefore, the nails no longer hold tightly. Wright says when horses walk in deep mud, the front feet are not moving out of the way fast enough before a hind foot catches a front shoe. And when hooves are saturated with water, shoeing them is like driving a hot nail through butter and expecting it to stay put, says Wilt.

Kraus notes other issues, including:

• Hooves becoming dry and cracking in dry and arid conditions.
• Stomping at flies, leading to the foot around the nail breaking down and the shoe loosening.
• Inadvertently raking the clinches down in the opposite foot while stomping flies.
• Catching a shoe on wire fencing.
• Poor nutrition leading to improper hoof growth and quality.

Tips to Reduce Rider or ­Management Issues

Overreach boots can help with front shoe loss, says Kraus. When fitted correctly, overreach boots contour to the heel bulbs and can be adjusted for a tight fit with the Velcro closure. Kraus says most bell boots do not fit securely enough and, in deep mud, snow, and sand, tend to rise upward, leaving the heels of the shoes exposed.

Quarter boots for pacing racehorses will prevent the hind foot from interfering and grabbing the diagonal front foot. Quarter boots are firm rubber boots designed to stretch around the hoof to protect the coronary band to the bulb of the heel, Wilt explains. They come in lefts and rights, with the tall side of the boot also protecting the medial (inner) side of the hoof. He cautions that these boots are designed to be worn only during training and racing.

Grab boots are another type of hoof protection for racing harness horses. They fit similarly to the quarter boots, except they are thicker and lower to the ground. They function like a bumper around your horseshoes, says Wilt. These are also only to be worn during workouts and racing.

Duct tape can be the trick for short-term turnout. Wilt says duct tape works well when you are just letting your horse relax and blow off a little energy between racing or training sessions. His formula for tape placement is as follows: Pull some tape out of the roll and position it so both heels are in the middle of the tape. Then wrap the tape around the front of the hoof (staying out of the hairline) and back down to line up with the tape you started the process with. Repeat this about three times around the hoof and cut the tape.

Pulling shoes during the off-season. If the horse has some down time, it can be better for him to go without shoes for that period, says Wright. Wilt agrees, noting that pulling the shoes and giving the horse a pasture trim can save you the time and costs of replacing lost shoes and repairing damaged hooves until the horse gets shod again.

Mud pads or high-traffic pads can be constructed as a pasture management measure to help keep mud to a minimum where horses congregate. A properly constructed pad can provide a sturdy surface for the horses to stand on and will reduce the formation of mud in that area. You can use a variety of techniques and materials when constructing a mud pad. Several university cooperative extension services provide literature and step-by-step instructions on constructing a mud pad area within your paddock or pasture (i.e., bit.ly/40B720W).

Fly leggings or bands might help reduce stomping due to flies. Leggings typically fit loosely and provide a screen or mesh barrier between your horse and the flies. Leg bands contain citronella to repel flies and attach loosely (a two- to three-finger fit) around the horse’s leg just above the fetlock. As with any product, you’ll need to follow the manufacturer’s recommendations for fit, use, and maintenance to see positive results.

Hoof supplements might be beneficial if you determine the horse’s diet is not optimal for hoof health, says Kraus. Equine nutritionist Amy Parker, MS, from McCauley’s Feeds, in Versailles, Kentucky, says hooves rely on an adequate supply of essential nutrients. The most common mistake is feeding less than the minimum required amount of a feed as directed by the manufacturer, which can lead to deficiencies, particularly in trace minerals and vitamins, she says. If all nutrient requirements are being met, then a hoof supplement containing biotin (minimum of 15-20 milligrams per day), the essential amino acid methionine (minimum of 2,500 milligrams per day), and zinc (minimum of 175 milligrams per day, but make sure you don’t feed more than 500 grams in the horse’s total diet) might help. Because you are affecting new hoof growth and not the hoof that is already on the ground, notes Parker, hoof supplements must be fed for many months before expecting results.

Horse-Caused Shoe Losses

Horses will be horses and can have too much fun running, bucking, and kicking, accidentally stepping on their own feet and pulling shoes, says Wright. Kraus says other potential horse-related shoe losses include:

• Nervous horses that aren’t paying attention to hoof placement might step on themselves and their shoes.
• Horses with behavior issues such as stall wall kicking, weaving, or pawing might loosen shoes.
• If a horse gets cast in a stall, he might pull a shoe while scrambling to get up.
• A horse that sticks his foot through a fence could pull the shoe off as he brings it back in.

Horse conformation can play a role in shoe loss. For example, long legs and a short back might allow the horse to overstep onto the heels of the front feet, while base-narrow hooves stand closer together, so the horse might step on the inside branch of the shoe. A base-wide, toed-out horse in front might also step on the inside heel of the shoe. Upright hoof conformation can also increase a horse’s likelihood of shoe loss.

Tips to Reduce Horse-Related Shoe Loss

A different turnout or pasture group can sometimes mitigate rambunctious running. Finding a group for your horse that elicits lower energy might limit shoe loss due to excessive play.

Wilt says the real headache with shoe loss is not being able to replace the shoe if a foot has been shredded due to heavy clinches. Cutting the clinches off allows the shoe to come off easily and without hoof damage if the horse does grab it. Even without heavy clinches the shoe stays tight.

Wilt explains that the art of trimming horses involves knowing the difference between how much foot can come off and what must stay.

Take-Home Message

Simple management or riding changes might be all you need to reduce the chances of your horse losing a shoe. Farriers must take all conditions into consideration, says Wright, including the horse’s disposition, routine, and environment and the barn’s management style when determining the best plan for limiting shoe loss.

Orthobiologics is a term encompassing a range of biological therapies that help a horse’s body repair itself from acute injury or chronic conditions such as osteoarthritis (OA). These therapies offer better long-term solutions than products that can cause complications when used over an extended period, said Beau Whitaker, DVM, CERP, of Brazos Valley Equine Hospitals in Salado, Texas, at the 2025 IGNITE Sports Science for the Olympic Disciplines Seminar, held Jan. 12-13, in Ocala, Florida. 

Deciding on an Orthobiologic for Use in Horses 

How do veterinarians decide which orthobiologics product to use? Typically, they look to their own and others’ anecdotal experiences, peer-reviewed research (mostly in humans), research or data provided by a company, and client preferences. 

Other factors veterinarians consider when deciding on a specific product include: 

1. Time frame 
   • What is the horse’s competition schedule? 
   • What is the withdrawal time of the product (i.e., how long before competition must the treatment be administered to comply with regulations)? 
   • Is the horse hurt or injured (versus giving an injection for maintenance purposes)? 

2. The effect relative to diagnosis 
   • Is the issue with soft tissue, the joint, or both? 
   • How severe is the injury/condition? 
   • How old is the horse? 

The ideal dosage for many orthobiologics remains unknown. Whitaker said veterinarians make the decision relative to joint size and pathological severity as well as anecdotal experience. To date there isn’t “clinical data evaluating dose response relative to product and condition treated,” he added. 

Orthobiologics for Equine Asthma 

In the second part of the discussion on orthobiologics, Dan Dreyfuss, DVM, MA, of D. J. Dreyfuss DVM LLC Consulting, in Hampstead, Maryland, spoke about using orthobiologics for respiratory diseases. 

Researchers conducted a small pilot study to look at the initial safety of nebulizing orthobiologics. Eight horses with mild asthma were evaluated and assigned a baseline weighted clinical score (WCS) based on nine respiratory-related clinical signs. They then received a series of six nebulizations at 48-hour intervals. The practitioners saw no significant safety issues, and seven out of the eight horses improved their WCS. 

Next came a larger pilot study where researchers repeated the same administration and evaluation protocol as in the initial safety study. Thirty out of 34 horses (88.2%) demonstrated a positive response to orthobiologics through nebulization. Results from these small studies are enough to encourage researchers to perform a larger study, said Dreyfuss. 

Take-Home Message 

“Orthobiologics are moving us in the right direction,” said Whitaker. Questions remain about the clinical data, required dosages, and product safety. 

Dreyfuss said it’s early in the process of using orthobiologics for horses with asthma, but he is encouraged by the significant clinical improvement in a large percentage of horses in the pilot study. 

With more time and research the different roles of orthobiologics in horses will become clearer, he added. 

Until recently, equine researchers knew little about how dopamine regulates insulin secretion in horses. In two recent studies scientists examined this connection, with implications for managing conditions such as pituitary pars intermedia dysfunction (PPID, formerly called equine Cushing’s disease) and insulin dysregulation (ID).

“A significant number of horses and ponies with PPID produce very large amounts of insulin in response to dietary nonstructural carbohydrates (starches, sugars, and fructans), and this puts them at increased risk of laminitis,” said Simon Bailey, BVMS, PhD, FHEA, Dipl. ECVPT, FRCVS, professor of veterinary biosciences at The University of Melbourne’s Veterinary School, in Victoria, Australia.

Bailey and a research team funded by the Australian Research Council, the Waltham Petcare Science Institute, and Boehringer Ingelheim Vetmedica, including PhD candidate Nicolas Galinelli, have been working to identify the link between PPID and insulin production so they can find ways to better reduce the risk of laminitis in and manage these horses.

Dopamine’s Role in Equine Insulin Response

“Horses and ponies with PPID have reduced dopamine production in the brain (which causes the production of certain hormones from the pituitary gland to get out of control), and we have recently found that it is decreased in the bloodstream as well,” said Bailey.

To investigate the link between dopamine depletion and insulin metabolism in horses, the researchers administered alpha-methyl-para-tyrosine (AMPT), a modified amino acid that inhibits dopamine production, to six healthy Standardbred horses in a placebo-controlled crossover study. Bailey and his colleagues aimed to determine how short-term dopamine reduction affects insulin sensitivity and postprandial (post-meal) insulin responses.

In healthy horses, insulin—a hormone produced by the pancreas—regulates blood sugar by signaling cells to take up glucose and store it as glycogen. In insulin-resistant horses, reduced sensitivity to insulin limits glucose uptake, prompting the pancreas to produce more insulin.

The researchers found that reducing dopamine levels in the horses led to increased postprandial insulin responses. “By temporarily reducing dopamine levels in the brain as well as in the rest of the body, we found that dopamine is not linked to the sensitivity to insulin (in horses, unlike in some other species), but depleting dopamine increases the insulin response to a high-glucose meal,” said Bailey. “Therefore, normal dopamine levels must be helping to keep insulin in check.”

Implications for Treating PPID in Horses

Bailey and his team used the study findings to explore the effects of pergolide—a drug commonly used to treat PPID in horses—on dopamine in horses and ponies with and without PPID. “This drug stimulates the receptors for dopamine, telling the pituitary gland to reduce hormone production, but now we find that it may also affect the pancreas, reducing insulin production,” said Bailey.

However, Bailey added that the drug only partially reduced postprandial insulin response to a high-starch meal, and horses without PPID did not benefit from treatment. “Therefore, in PPID animals or those with equine metabolic syndrome, who are at risk of laminitis due to high insulin levels, they still need to be fed diets low in starch and sugars to avoid excessive insulin levels. Pergolide will not protect them from the effects of high-carbohydrate diets (including lush grass).”

Take-Home Message

Dopamine influences insulin secretion in other species, but its role in equine metabolism has been unclear. Many horses with PPID also experience ID, marked by heightened insulin responses and an increased risk of laminitis. Researchers are still exploring the link between dopamine and insulin production and how this information can be used to more effectively treat horses with metabolic problems. Pergolide had no effect on tissue insulin sensitivity; however, the study results suggest that postprandial hyperinsulinaemia might be limited by this dopamine receptor agonist in animals with PPID and ID. If your horse has metabolic issues, work with your veterinarian to develop an appropriate management and treatment plan.

“We are certainly doing more research in this area to try to better understand these conditions (PPID, EMS, and laminitis) and how they fit together,” said Bailey. “These are such common conditions with huge effects on the well-being of our horses and ponies, so we need to do everything we can in the effort to find new treatments and countermeasures.”

The first study, “Effect of short-term dopamine reduction on insulin sensitivity and post-prandial insulin and glucose responses in Standardbred horses,” was published in Domestic Animal Endocrinology in January 2025. The second study, “Effect of pergolide treatment on insulin dysregulation in horses and ponies with pituitary pars intermedia dysfunction,” was published in Equine Veterinary Journal in February 2025.

Lameness arising in the front feet accounts for most soundness issues in horses. However, it has been and continues to be difficult for veterinarians to diagnose a specific injury or source of pain within the foot because the structures can be tough to capture with imaging equipment. Over time, as medical knowledge has expanded, radiography has improved, and MRI has been incorporated into equine practice, we’ve learned a lot about the hoof capsule’s complex anatomy and physiology. The more we understand, the more injuries we can identify. This knowledge has opened doors to many treatment options in the veterinarian’s toolbox. With an accurate diagnosis, the veterinarian can formulate a proper treatment plan and provide an accurate forecast on the horse’s ­prognosis.

In spite of these advances, it’s still important for veterinarians to complete a thorough clinical exam. Visual and hands-on assessment of the horse can provide important clues as to the problem. This information often yields a wealth of knowledge that will help guide the need for diagnostic imaging.

History and Signalment

Knowing the horse’s age, breed, and use, as well as the duration of lameness and how quickly it came on, can help the veterinarian formulate a list of possible correlating problems. For example, a 6-year-old Warmblood show jumper coming up lame following a recent class might be dealing with a soft-tissue injury. Alternatively, a 17-year-old Quarter Horse used for team roping with intermittent forelimb lameness over several months might be dealing with a joint or bone-related injury.

Lameness Exam Findings

A veterinarian can learn much and narrow down possible problems simply by completing a thorough clinical exam. Clues that can help include:

• How the horse moves and travels on different surfaces (packed dirt vs. loose sand);
• How the foot lands and takes off from the ground during travel;
• The lead on which the lameness is most pronounced;
• Response to hoof testers; and
• Response to flexion tests.

Additionally, veterinarians can learn a lot by evaluating hoof capsule conformation and health. Distortions in growth, weakness of the hoof walls, contraction of the heels, and uneven wear of the wall or shoe can result from pain or injury in different parts of the foot, how the horse compensates, and predisposing factors to specific injuries.

Finally, they might be able to determine the cause of lameness with specific diagnostic nerve blocks. Using a local anesthetic drug, the veterinarian can desensitize different parts of the foot to detect the location of pain within the hoof capsule. For example, the commonly used palmar digital nerve block desensitizes the sole and back third of the foot, whereas a navicular bursa block generally targets that structure—which cushions the bone from the deep digital flexor ­tendon—alone. Following a nerve block, the vet assesses the horse to see if he travels differently.

Based on these exam findings, the veterinarian can use digital radiography to assess suspected bony problems, then pursue more advanced imaging if ­necessary.

High-Tech Diagnostics

Magnetic resonance imaging has been labeled the “gold standard” for veterinarians to image the horse’s foot. It can provide detailed information about soft tissue, bone, and fluid within the hoof capsule. It can often help veterinarians identify abnormalities they may not otherwise recognize using other diagnostics. Evaluating the horse’s foot using MRI is noninvasive, safe, and can be done with good accuracy either in a standing sedated horse or a horse lying down under general anesthesia. Though MRI is a great option, it does pose some limitations. It’s expensive, and in some parts of the country MRI unit availability is limited. Additionally, MRI imaging requires interpretation by a trained professional and often reveals more than one abnormality. For this reason veterinarians often look for other clues to help pinpoint a horse’s problem before pursuing an MRI exam or, later, to help determine the significance of the MRI findings.

Take-Home Message

In summary, front foot lameness is common and continues to frustrate horse owners and challenge veterinarians. Fortunately, owner-provided information and a thorough lameness exam can help practitioners start meaningful investigations. MRI has improved our understanding of the horse’s foot and serves as a valuable tool but is not an absolute necessity.

While diagnostic imaging technology and treatments for equine back pain have improved in recent years, the clinical examination remains a vital part of accurately diagnosing and treating spinal problems in horses. “Ninety-four percent of ridden horses experience back pain,” said Sandro Colla, DVM, MS, postdoctoral fellow at Colorado State University’s College of Veterinary Medicine & Biomedical Sciences, in Fort Collins. Colla explained the role of the clinical examination and functional assessment in diagnosing back problems in horses during his presentation at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida.

Equine Back Anatomy and Biomechanics

The horse’s back includes fascia, muscles, tendons, ligaments, and bones, which work together to support the horse as he moves and works. The fascia is a layer of connective tissue that surrounds muscles, providing support and structure. It contains nerve endings that can sense and send pain signals. Muscles and tendons work together to coordinate skeletal movement and provide stabilization at rest and during work, while bones protect the spinal cord and provide greater structural integrity, said Colla. Each piece of the horse’s back anatomy allows him to flex and extend both laterally (side-to-side) and longitudinally (dorsal-to-ventral) during forward and back global body movements—coordinated movements that utilize multiple muscle groups across the entire body to generate significant motion.

Dysfunction in the Equine Back

“Anything that impairs the physiological and biomechanical activities (of the spine) is considered dysfunction,” said Colla. Mechanical dysfunction renders tissues unable to execute their expected function and frequently has high clinical relevance, he added. Dysfunction caused by pain can be acute (conditions that develop suddenly and are often severe but short-lived), subacute (less sudden/severe), or chronic and observed in the horse’s posture, during palpation, and in spinal mobilizations.

“Horses can demonstrate normal, reduced, or increased spinal range of motion during examinations,” said Colla. This might be isolated to one joint or a whole segment due to bony changes, adhesions, abnormal muscle tone, or fascia pain, he added. “The clinical relevance of range of motion changes can vary but is usually associated with other dysfunctions.”

Veterinarians might also observe misalignments in the horse’s spine during examination, which can be isolated or evident throughout an entire segment of the spine. Misalignment can be congenital (present at birth) or acquired (developed after birth due to external factors) and generally has a variable clinical significance, said Colla.

Assessing Equine Back Pain

During a clinical examination, veterinarians should inspect the standing horse’s structure, noting any abnormalities or pathologies (disease or damage) found using palpation or imaging. However, the functional assessment allows practitioners to determine the clinical relevance of these findings and determine whether they affect the horse in his work, said Colla. “The functional assessment should be dynamic and include performance-related work.”

During an assessment Colla said veterinarians should ask clients to describe how long a horse has shown signs of back pain, characteristics of the horse’s pain, previous treatments and their successes, current athletic performance, and intended future use. They should inspect the horse both at rest and in motion and observe muscle development and any asymmetries. Then, using light palpation, they should locate any vertebral misalignment, increased temperature on any part of the back, or abnormal pain sensations.

“Gradually increase force applied to any structures of interest,” said Colla. “Find trigger points and put pressure on exactly that point to observe the horse’s reaction.”

Veterinarians can also observe how the horse moves during spinal mobilization exercises including sternal lifts, lateral bending/rotation, and lumbosacral flexions, said Colla.

Using objective measurement tools can help veterinarians accurately quantify abnormalities in a horse’s back. Colla said he often uses a flexible ruler to draw the contour of a horse’s spine to determine if his posture changes at any point during the rehabilitation, a pressure algometer to quantify pain, and a noncontact infrared thermometer to measure any areas of increased heat. He also takes pictures of the horse to refer to later if needed.

Diagnosing and Treating Equine Back Pain

“For horses with mechanical dysfunction, (veterinarians) can take radiographs, ultrasound, computed tomography, or bone scan (or a combination of several) to help determine the site of dysfunction,” said Colla.

In horses with dysfunction caused by pain, he uses these imaging modalities to locate any pathologies in the back. He also recommends manual therapies, systemic or local medications, acupuncture, extracorporeal shock wave therapy, and therapeutic exercises for rehabilitation.

Colla treats horses with range-of-motion restrictions using therapeutic exercises, manual therapies, and in cases of misalignment, chiropractic adjustment. The only way to treat misalignments is with chiropractic adjustments, he added.

Take-Home Message

Diagnostic technologies and treatments for equine back pain have improved in recent years, but clinical examination and functional assessment are still important for locating clinically relevant pathologies in a horse’s back. Veterinarians should approach each patient as an individual and develop a treatment plan based on the horse’s unique pain and the owner’s plans for the animal.

What joint therapy (if any!) is right for your horse?

With the summer show season just around the corner, now is the time to start preparing your horses for success. However, diving into intense training can take a toll on your horses’ joints, potentially leading to issues right when you need them performing their best.

In this article we’ll learn how common joint issues, primarily osteoarthritis (OA), concern owners of competitive horses. Then we’ll look at preventive and therapeutic approaches to manage this chronic, invariably progressive performance-limiting condition.

Why Focus on Equine Joint Health?

Results from several recent studies reveal that many horse owners view musculoskeletal conditions as a major health concern. For example, in one survey of 246 horse owners, researchers found that 29.2% of survey respondents listed stiffness and reduced leg/joint flexibility as a major concern (Herbst et al., 2024). Osteoarthritis was the most common owner-reported, veterinary-diagnosed medical condition, occurring in 32.6% of horses owned by survey respondents. That survey included horses 15 years or older actively involved in low-, medium-, and even high-level (international) competition.

Another research group conducted an online survey of 1,677 owners of British eventing horses about lameness and illness (Tranquille et al., 2024). Of those, 26% relayed having a lameness/musculoskeletal issue in the previous six months, with joints being the second most frequent source of the lameness (382 horses). The most commonly affected joints included the tarsus (hock), stifle, forelimb distal interphalangeal (coffin) joint, metacarpophalangeal (forelimb fetlock) joint, and the carpus (knee).

Joint issues disrupt training and competition. In the Tranquille et al. survey, owners reported that horses with fetlock and hock injuries were off work for about two weeks. Stifle and coffin joint problems often required layups of up to six months.

Preventing OA, Slowing Progression for Equine Joint Health

Osteoarthritis often begins with low- to medium-grade inflammation (i.e., synovitis or inflammation of the joint’s inner lining) where there might not be any cartilage or bone changes.

“But if left unchecked, this condition can progress, affecting other tissues in the joint, including the cartilage lining the ends of bones inside joints and the layer of bone directly under the cartilage called the subchondral bone,” explains Laurie Goodrich, DVM, PhD, Dipl. ACVS, professor of surgery and lameness at Colorado State University’s (CSU) Johnson Family Equine Hospital and director of the Orthopaedic Research Center, in Fort Collins. “As OA advances, the cartilage and subchondral bone lose their ability to support the necessary mechanical forces that are required of them.”

“Ultimately, OA permanently changes the joint environment where cartilage is thinned or lost, the bone underneath it becomes thickened (sclerotic), the joint capsule loses its pliability, and the joint becomes stiff. These are all characteristics of career-limiting OA,” says Goodrich.

No cure exists for OA, which means vets focus on prevention and slowing progression to maintain joint comfort and athleticism.

Potential ways of preventing OA include:

• Maintaining an appropriate body condition score (BCS). Excess condition and body weight can hasten the incidence of arthritis development, as has been observed in dogs and humans (Pratt-Phillips and Munjizun, 2023).

• Prophylactically administering joint supplements in healthy horses before joint trauma, inflammation, and evidence of OA (van de Water, 2016, and Leatherwood, 2016). However, not all joint supplements are backed by scientific evidence, so it’s best to discuss your options with your veterinarian.

• Focusing on proper training and conditioning while avoiding overtraining. “Muscles, tendons, and ligaments are critical for supporting joints and need to be conditioned to do the job that is expected of them—just like human athletes,” says Kyla Ortved, DVM, PhD, Dipl. ACVS, ACVSMR, associate professor of large animal surgery at the University of Pennsylvania’s New Bolton Center, in Kennett Square.

• Making sure athletes are shod to their conformation and properly supported.

Treating OA? Diagnostics First

When preventive measures can no longer maintain joint comfort, owners have various treatment options at their disposal. However, an accurate diagnosis of joint discomfort is needed; otherwise, the horse will not respond as expected to therapies, including intra-articular (IA) medications. In turn, this can delay return to work/competition or lead to continued poor performance.

In a standard lameness exam your veterinarian will watch the horse walk and trot and will perform flexion tests and diagnostic analgesia (joint blocks with a local anesthetic such as lidocaine) to try to identify the painful joint(s). Radiographs (X rays) can reveal pathology—disease or damage—including conditions such as osteochondritis dissecans (OCD) and intra-articular fractures that can lead to OA.

“Radiographic changes associated with OA can be seen in more advanced cases where bony reaction or loss of cartilage has already occurred,” explains Ortved.

In cases of early OA, however, advanced imaging, such as computed tomography, MRI, and positron emission tomography (PET) can be very useful, she adds.

After diagnosing OA and ruling out other issues, it’s time to consider treatment if preventive measures fall short.

Choosing the Right Intra-Articular Therapy for Equine Joint Health

The tried-and-true often first-line intra-articular medications that many owners would be familiar with for OA are corticosteroids, such as triamcinolone. Appealing features of corticosteroids include their low cost and widespread immediate availability. While these medications effectively reduce inflammation and discomfort, they do come with some drawbacks.

“First, depending on the corticosteroid and the frequency of usage, corticosteroids may negatively affect cartilage metabolism, ultimately hastening cartilage degeneration and worsening osteoarthritis over time,” says Goodrich.

Second, even corticosteroids administered within a joint can have systemic effects. Page et al. (2024) reported that a 9-milligram dose of intra-articular triamcinolone results in abnormal findings for the thyrotropin-releasing hormone test used for diagnosing pituitary pars intermedia dysfunction (PPID, aka equine Cushing’s disease) as well as the oral sugar test used for diagnosing insulin dysregulation. The IA triamcinolone also results in increased circulating levels of glucose and insulin, which could predispose horses to laminitis. Hallowell et al. (2024) also reported systemic effects of intrasynovial triamcinolone.

Third, corticosteroids simply control clinical signs associated with OA and do not play any role in modifying the course of disease/slowing disease progression. For this reason researchers such as Ortved and Goodrich direct their attention toward regenerative therapies, also called orthobiologics. These are treatments derived from biological substances to treat musculoskeletal conditions.

IA Corticosteroid Alternatives for Equine Joint Health

ACS

Autologous conditioned serum (ACS) is an orthobiologic created by collecting a blood sample from the patient and using a commercial kit to produce interleukin-1 receptor antagonist protein (IRAP, produced by incubating the blood with special beads) and other anti-inflammatory molecules. The IRAP blocks interleukin-1, a powerful and damaging pro-inflammatory mediator. The incubation process also stimulates the production of anti-inflammatory mediators and growth factors similar to those found in platelet-reduced plasma (PRP, more on this a moment). The vet then injects this “conditioned” serum into the target joint to inhibit inflammation.

In terms of efficacy, Tommasa et al. (2023) relayed in a systematic review of the literature that while most studies on ACS support this joint therapy for OA without significant adverse effects, some studies were poorly designed (e.g., lacked a control group). The researchers concluded that a “more rigorous approach to validate the efficacy of ACS in OA treatment” is needed.

Ortved did point out several studies, however, in which authors reported a good therapeutic effect, such as Frisbie et al. (2007) and Lasarzik et al. (2018).

APS

Like ACS, autologous protein solution (APS) is rich in growth factors and anti-inflammatory proteins.

In Ortved’s most recent study on APS (Usimaki et al., 2024), the research team created synovitis using interleukin-1β in one hock joint each of 18 horses. Twenty-four hours later they treated 12 joints with APS and left six untreated (control group). Although they did not report any changes in lameness or joint circumference (a measure of joint effusion/inflammation), they noted a significant improvement in gross joint appearance and the microscopic structure of joint synovial lining, suggesting APS has a disease-modifying effect on OA.

In Ortved’s hands, APS is more popular because it does not need to be incubated overnight like ACS does. Veterinarians also usually repeat ACS injections once weekly for a total of four doses, which in Ortved’s hospital setting is not easily accomplished.

Still, “I know many veterinarians that use ACS in the field and really like it,” she says.

At CSU, Goodrich and Erin Contino, DVM, Dipl. ACVSMR, are leading a large ongoing clinical trial to compare the therapeutic results of APS to those of corticosteroids in the stifle joint.

Platelet-Rich Plasma

Vets produce PRP by collecting and centrifuging a blood sample using a commercial system, then injecting platelets intra-articularly. The platelets, when activated, release growth factors and a number of other proteins.

In a recent review of five studies on PRP treatment for OA, researchers reported a “significant improvement in the PRP products treatment group compared with the control group.” Thus, Peng et al. (2024) concluded, “PRP products as intra-articular treatment are likely efficacious for treatment of equine OA,” but more blinded and randomized trials are needed.

Stem Cells

After collecting autologous (originating from the patient) or allogeneic (from another horse) stem cells from bone marrow or adipose tissue, the vet processes and injects these cells directly into joints, where they exert anti-inflammatory and immune-modulating properties and recruit other stem cells within the joint to facilitate healing.

Systemic, Other Therapies

Veterinarians still recommend nonorthobiologics such as intramuscular polysulfated glycosaminoglycan. This has been described to help restore the steady state between production and destruction of cartilage components, helping keep things on the right path in horses with early signs of joint inflammation or OA. They also prescribe hyaluronic acid (HA, the body’s natural joint lubricant) joint therapy, injecting hyaluronate sodium intravenously or IA to promote cartilage health and joint lubrication and reduce inflammation.

Polyacrylamide Hydrogels

Available commercially as 2.5% or 4% products, polyacrylamide hydrogels are the newest additions to the IA arthritis armamentarium. The Food and Drug Administration says hydrogels are not orthobiologics but, rather, “medical devices.” The suggested mechanism of action for the 2.5% product is that the hydrogel integrates into the joint’s synovial lining and changes the cellular properties with an increase in macrophages—white blood cells that surround and kill microorganisms, remove dead cells, and stimulate the action of other immune system cells—that can be anti-inflammatory (Lowe et al., 2024).

“It is also possible that the integration leads to changes in the elasticity of the synovial membrane, improving biomechanics in the joint. This property is currently being studied,” says Ortved.

In a study by McClure et al. (2024), the 4% hydrogel reportedly provided long-term joint lubrication with no adverse effects noted after serial injections once every 45 days for a total of four injections.

De Clifford and co-authors provided data supporting hydrogel use for lameness in 2021. That group reported the 2.5% hydrogel “led to statistically superior results compared to triamcinolone and HA in the management of selected middle carpal joint lameness in flat-racing Thoroughbreds, with therapeutic effects persisting up to 12 weeks.”

Take-Home Message

“In my opinion,” Ortved says, “orthobiologics should be used before corticosteroids if the situation is the right one … owners are willing to be a little patient to see an effect (i.e., several weeks) versus needing a change immediately, as can be seen with steroids.” Goodrich says she believes “the advantages of orthobiologics outweigh the increased cost (versus corticosteroids) because the approach is both anti-inflammatory as well as regenerative, and ultimately longevity of athletes’ joints is the goal.”

This article is from the Spring 2025 issue of The Horse: Your Guide to Equine Health Care. We at The Horse work to provide you with the latest and most reliable news and information on equine health, care, management, and welfare through our magazine and TheHorse.com. Your subscription helps The Horse continue to offer this vital resource to horse owners of all breeds, disciplines, and experience levels. To access current issues included in your subscription, please sign in to the Apple or Google apps OR click here for the desktop version.

Veterinarians can use positron emission tomography (PET), computed tomography (CT), or magnetic resonance imaging (MRI) to help diagnose problems in equine patients, but how do they choose which to use? Timothy Manzi, VMD, Dipl. ACVR-EDI, clinical assistant professor of large animal diagnostic imaging at the University of Pennsylvania’s New Bolton Center, in Kennett Square, and Myra Barrett, MS, DVM, Dipl. ACVR-EDI, associate professor of equine diagnostic imaging at Colorado State University’s College of Veterinary Medicine, in Fort Collins addressed this nuanced question at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida.

Positron Emission Tomography in Horses

More veterinarians are using positron emission tomography for its unique capabilities. Paired with motion-correcting software, PET can tolerate minor movement, making the modality ideal for use under standing sedation, rather than anesthesia, they explained.

Used both for screening and follow-up evaluations, PET scans allow the veterinarian to assess all four feet in 20 minutes and structures as high as the proximal suspensory ligament and distal (lower) knee and hock in most horses. The veterinarians agreed the modality excels at detecting subtle issues such as impending sesamoid fractures, which veterinarians might miss on standard radiographs. Positron emission tomography is popular in both racehorse and sport horse practice because it allows practitioners to identify subchondral bone injuries early.

Computed Tomography in Horses

Significant advancements in CT technology have enhanced its use in equine medicine. Specifically, fan-beam CT produces high-resolution images and can be performed under standing sedation. The alternative, cone-beam CT systems, acquire volumetric data (used to display a 2D projection of a 3D sample) but the veterinarians agree these systems are more prone to artifacts (unintended distortions) and less effective for soft tissue evaluation compared to the fan-beam CT.

Small-animal practitioners use cone-beam CT for dental imaging. Manzi said it has more limited use in equine medicine but still offers some good utility.

Veterinarians can also use CT to diagnose vertebral pathologies (disease or damage). Used in combination with myelogram contrast, CT can reveal spinal cord compression undetectable by radiographs. For imaging of the equine pelvis, the modality offers better detail than some other imaging modalities, uncovering conditions such as sacroiliac lysis that were previously only diagnosed post-mortem.

Magnetic Resonance Imaging in Horses

Magnetic resonance imaging remains a cornerstone for diagnosing soft tissue injuries and bone-marrow lesions, including bone bruises with fluid and contusions. While Manzi and Barrett described low-field standing MRI as more accessible, they agreed it is prone to motion artifacts and offers less detail than high-field MRI conducted under general anesthesia.

Diagnostic Imaging in Equine Practice

Veterinarians often use a mixture of imaging techniques to assemble the puzzle pieces they need to reach a diagnosis. Combining MRI or CT with PET can create a comprehensive picture, compensating for the blind spots of each modality. For instance, contrast-enhanced CT outperforms standing MRI in cartilage evaluation, while ultrasound remains superior for some tendon and ligament injuries, the clinicians explained.

Cross-sectional imaging (MRI, CT, and PET, which show slices of the structure imaged) can be particularly valuable when radiographs fail to reveal the source of lameness—in the case of bone marrow lesions, for example, said Manzi. To avoid client disappointment and frustration with inconclusive scans, both veterinarians recommend preprocedural education about the capabilities and limitations of each technology.

The Role of Artificial Intelligence

Artificial intelligence advancements attempt to simplify image acquisition and provide motion control, but that’s where its usefulness currently ends. “Imaging interpretation fully remains in the hands of veterinarians,” Manzi said.

Take-Home Message

Advanced imaging modalities can provide precise answers for equine practitioners, contributing to more precise treatments and better prognoses. Evolving PET, CT, and MRI technologies improve veterinary diagnostic capabilities, offering precise insights into pathologies that were previously difficult to define, and refine the way veterinarians identify and manage lameness in horses.

“Competing horses should not show clinical signs of pain,” said Lori Bidwell, DVM, Dipl. ACVAA, CVA, co-owner and founder of East West Equine Sports Medicine, based in Lexington, Kentucky.

“… And a horse needing daily pain medication shouldn’t be competing,” added Richard Markell, DVM, MRCVS, MBA, owner of IlluminX Consulting, in Encinitas, California.

Bidwell and Markell addressed the medical and ethical challenges of managing pain in sport horses during their presentation at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11 in Orlando, Florida.  

Balancing Equine Medicine with Ethics

Managing pain in performance horses responsibly can be complex. Veterinarians must balance animal welfare with the expectations of owners and trainers in competitive equine sports. “First of all, true pain must be differentiated from transient ‘day after the gym’ soreness,” Markell said.

“Persistent pain often signals underlying issues like musculoskeletal injuries or gastric ulcers, which should be investigated and ruled out rather than masked by pain medication,” Bidwell added, underscoring veterinarians’ responsibility to act as advocates for horses.

The Effects and Legalities of Different Medications

Veterinarians commonly use various pain medications in horses, including the nonsteroidal anti-inflammatory drugs (NSAIDs) phenylbutazone and flunixin meglumine (Banamine), as well as bisphosphonates to reduce pain and extend the careers of performance horses. Bidwell and Markell warned that overuse and misuse of these medications can lead to significant risks.

Markell cautioned against overrelying on medications, pointing out that masking pain can exacerbate injuries. “For example, bone edema (fluid within the bone) can progress to fractures if horses live on Banamine while competing,” he said.

Bisphosphonates are FDA-approved for treating podotrochlosis (navicular disease) in horses, but veterinarians sometimes use them off-label in equine athletes. Bidwell advocates for strict regulation and responsible administration of these drugs, which slow down bone turnover.

Alternatives to Pain Medication

Bidwell and Markel stressed the importance of using the least amount of medication necessary to keep a horse pain-free. Drug-free alternatives such as acupuncture and homeopathic remedies, though less conventional (and only legal under certain governing bodies in the case of homeopathy), might offer safer ways to manage pain and inflammation in horses. For example, while Traumeel (a homeopathic remedy containing plant and mineral extracts designed to address pain and inflammation) is not considered legal under United States Equestrian Federation (USEF) rules, Zeel and arnica are allowed, said Bidwell.

Both veterinarians agreed that extracorporeal shock wave therapy (ESWT) provides valuable benefits, particularly for treating back and sacroiliac pain in horses. However, its ability to mask pain calls for careful oversight. Recent changes to USEF rules now mandate that only veterinarians or their supervised technicians can administer shock wave treatments on show grounds.

Regulations to Protect Horses

Regulatory frameworks from organizations such as the Fédération Equestre Internationale (FEI) and USEF help curb unethical pain management practices for sport horses. These regulations notably restrict NSAID use to prevent overmedication and level the playing field. Because misuse of medications—particularly in high-stakes environments—sometimes stems from misguided client expectations, Bidwell stressed the need to educate horse owners and young veterinarians to prioritize long-term welfare over immediate results. “We must advocate for the horse’s health, not just its performance,” she said.

Take-Home Message

Treating pain in performance horses remains a controversial topic. New innovations and improvements in equine medicine extend equine athletes’ careers. In addition, new regulations from USEF and the FEI aim to protect horses from inappropriate and unethical use of pain-masking medications and modalities at competitions. Bidwell and Markel encouraged equine practitioners to advocate for the horse above all else when faced with ethical dilemmas in pain management.

We may be in the thick of winter at press time, but spring will be here before we know it—and with it the traditional spring vaccines. You might have noticed some equine vaccines are available over the counter for anyone to purchase and administer. However, when a veterinarian is not involved, this approach to preventive care can be seriously detrimental to the overall health of the horse for several important reasons.

First and foremost, the relationship between an equine owner and her veterinarian is an important bond and one that should be established on a routine basis, not in an emergency. Equine veterinarians are becoming few and far between, meaning that those who are still in practice might not be able to take on new clients during emergency hours. Building a good working relationship with a veterinarian you trust ensures that emergency care is available and that the practitioner is familiar with your horse and his unique medical needs and history.

Annual Wellness Exams

Second, vaccinations are only part of your veterinarian’s annual visit. Just like annual exams for children, complete physical examinations at these visits can help the practitioner pick up on changes in your horse’s health, such as new heart murmurs, hair and coat changes, weight gain or loss, or the development of or change in abnormal lumps or bumps. Problems are easier to manage or treat when identified early, as opposed to waiting until they are an emergency. This visit is the perfect time to discuss concerns you have, including diet, exercise, and temperament, follow up on previous emergency or sick visits, or clear up rumors you’ve heard floating around on social media. This is where you, your horse, and your veterinarian build camaraderie—again, the relationship necessary for quality emergency care from a friendly face when you need it!

Parasite Control

Third, annual visits from your veterinarian allow discussion and completion of other components of preventive care. Our understanding of parasites has changed the way we approach deworming—fecal egg counts enable us to give more specific recommendations for parasite control programs for individual horses and herd situations. Traditional rotational deworming and other programs have fallen out of favor, and veterinarians are the most knowledgeable on this topic.

Dental Care

At the other end of the horse, it’s important to have a veterinarian perform dental care; it is otherwise illegal in many states (Google your state’s stance on licensed dental care professionals and veterinarian supervision). Proper speculum examinations allow a veterinarian to evaluate the entire mouth and carry out any procedures they find necessary at that time, such as floating or extractions. Your practitioner might recommend specific sedation, local anesthesia, or antibiotics that are safe for your specific horse based on the physical exam.

Vaccinations

Finally, veterinarians can indeed administer vaccines. But, more importantly, they can recommend a specific vaccine program that is appropriate for your horse in your area. Not every horse needs every vaccine. For example, horses that travel need more vaccines than ones that stay at home. Maybe there is an outbreak of a disease in the area. Some horses react poorly or inefficiently to specific vaccinations and need medication ahead of time or afterward. No one knows the medical needs of your horse and your herd better than your veterinarian … not the feed store cashier.

Additionally, many vaccine companies are confident enough in their products that they offer financial support for diagnosis and/or treatment in the case of a vaccine failure. However, they will only provide this if a veterinarian administered the vaccine. This is to ensure proper handling (you’d be surprised how many expired vaccines—or vaccines stored at incorrect temperatures—I’ve found) and administration.

So, while you’re huddled under a blanket with your calendar planning your spring riding activities, I encourage you to consider the benefits of including veterinarians in your horse’s preventive care. They’d really like to see you during daylight hours when your horse isn’t sick!

Equestrian sports demand advanced skills and can involve extensive physical effort from both horses and riders. No horse is born with the capacity to perform at the highest level, which is where training comes into play. “We want the body to adapt to training,” said Tim Worden, PhD, an equestrian sport scientist located in Toronto, Ontario, during his presentation at the 2025 IGNITE Sports Science for the Olympic Disciplines Seminar, held Jan. 12-13, in Ocala.

But how do you prepare a horse to perform at the highest level of sport? What lessons can be taken from human athlete training and applied to horses?

Lessons for Training Equine Athletes

Lesson #1: Be flexible with planning. “Two steps forward one step back” is the traditional saying, and it’s typically true. Worden said it’s always good to have a plan, but you also need to remember it’s just a framework. Your horse needs daily monitoring. Watch the horse in the stall, during warmup, and during competition or training. Take notice of any changes (good or bad) and be ready to adjust your plan.

Lesson #2: If it matters, measure it. Are you and/or your horse getting better? You need to assess that somehow. Wearable sensors, smartphone applications, and software platforms might help, but it doesn’t have to be that elaborate. You can record your observations in notebooks or spreadsheets.

Lesson #3: Use exercises that must be solved in the desired way. The most effective training exercises mimic what you’ll be doing in competition and stimulate the same muscle patterns but are varied enough to keep routines fresh and engaging. Taking horses out of the arena and doing something faster (like a controlled gallop) than they typically go would be one way to do that, Worden said.

Lesson #4: Guide athletes along the safest possible path. Minimize injury and setbacks by managing risk factors. Worden explained that high-risk events include travel; issues with hoof trimming, shoeing, and conformation; psychological challenges; tack and equipment changes; and stress. The better you manage high-risk activities the more you can reduce the likelihood of injuries.

Take-Home Message

To help advance a horse’s training, observe his behavior daily, watch how he moves during work and around the barn, and understand what that is telling you about his strengths and weaknesses. Track your horse’s progress over time. Utilize exercises that naturally encourage the horse to move in the desired or correct way and, as your primary goal, avoid injuries.

Equivalent to the human knee, the equine stifle is an intricate assembly of bone, joint, and soft tissues. Problems with the stifle commonly cause pain and lameness in equine athletes. Cathleen Mochal-King, DVM, MS, Dipl. ACVS-LA, associate clinical professor and service chief of equine surgery and medicine at Mississippi State University’s College of Veterinary Medicine, described how veterinarians diagnose and treat stifle-associated lameness at the 2025 Veterinary Meeting and Expo, held Jan. 25-29, in Orlando, Florida.

Diagnosing Stifle-Associated Lameness

Three joints make up the stifle, but no single joint compartment communicates with all articular (related to the joint) spaces; in other words, there is no continuous fluid connection among them. This means veterinarians need to perform multiple nerve blocks and joint injections, said Mochal-King. She added that veterinarians should be aware of the anatomy of the meniscus, the fibrocartilage found between the femur and the tibia. There are two menisci in each stifle: one medial (toward the horse’s center line) and one lateral. Both can tear, causing performance-limiting pain and lameness.

During soundness exams Mochal-King said she looks for a wider base stance in the hind limbs as an indicator of potential stifle issues in horses. She also observes how the height of the tuber coxae—a bony projection on the pelvis, located on the ilium and often called the point of the hip—varies between the left and right sides as the horse moves, which can help pinpoint the lame limb. After physical and gait examinations, Mochal-King performs flexion tests and nerve blocks to localize the lameness.

When she incorporates radiography into her diagnostic approach, Mochal-King said she likes to extrapolate as much information from the images as possible. “People aren’t reading X rays as well as they used to because we’ve got other diagnostics now, but there’s a lot that you can see on a radiograph,” she said, pointing to—for example—subtle changes such as flat condyles (the typically rounded articular surfaces of the femur or tibia become flattened) that can predispose a horse to medial meniscal tears.

Combining Ultrasound-Guided PRP Injections With Adjunct Therapies

Mochal-King said she treated 15 meniscal tears in 2024 and had success using ultrasound-guided platelet-rich plasma (PRP) injections in the standing patient. “In addition to its regenerative properties, PRP acts like tissue glue to help heal the tears,” she explained. She said she was particularly meticulous about injection site preparation and added amikacin (an antibiotic) to the injection to reduce the risk of septic arthritis.

She said she also used shock wave therapy for stifle lameness because it “really helps with the fiber pattern and in strengthening the collagen pattern throughout tendons and ligaments.” Out of the 15 meniscus tears she saw in the past year, all but one patient went back to work.

Surgically Managing Stifle Lameness

When a stifle injury warrants surgical intervention (i.e. it cannot be successfully managed with rest, rehabilitation, and/or medical treatment), Mochal-King said she prefers coupling arthroscopic debridement with PRP injection. She’s also had success with drilling and curetting (scraping to remove tissue) subchondral bone cysts from the outside rather than entering the joint. With this type of surgical procedure, she emphasized the importance of horses returning to controlled exercise following the procedure, typically 60 days post-surgery.

Successful Outcomes and Final Thoughts

Performing a thorough assessment can help veterinarians successfully diagnose stifle lameness in horses. Mochal-King said she prefers to treat common stifle-associated lameness problems, such as meniscal injuries, with PRP and shock wave, only turning to surgery as needed.

The Kester News Hour at the annual American Association of Equine Practitioners Convention highlights key advancements in equine research. In 2024’s edition leading veterinarians shared their top picks from recent studies in their area of practice interest. This rapid-fire session offers valuable insights into the latest findings from equine scientists worldwide.

Kyla Ortved, DVM, PhD, Dipl. ACVS, ACVSMR, an associate professor of large animal surgery from the University of Pennsylvania’s New Bolton Center, in Kennett Square was once again invited to present what she considered the most interesting, influential, and clinically relevant studies pertaining to the equine musculoskeletal system.

Study 2.5% and 4% Polyacrylamide Hydrogel (PAAG) in Horses

In the first study she described (Lowe et al., 2024), researchers characterized how a 2.5% synthetic cross-linked injectable polyacrylamide hydrogel (2.5% iPAAG) integrated with synovial (joint) fluid when they injected it into joints. In total the researchers injected 13 fetlock or knee joints with either 2 or 4 milliliters of 2.5% iPAAG, said Ortved.

They performed follow-up examinations on the horses on Days 0, 4, 42, and 90 after injection and found white blood cells in the synovial membrane (the joints’ inner lining) consistent with a reaction to a foreign body. By Day 42 they found the iPAAG completely integrated into the joint’s synovial membrane lining. “No adverse effects at one or two times the recommended dose was appreciated,” she added.

Ortved presented a second study (McClure et al., 2024), in which researchers conducted serial 4% PAAG injections in horses on Days 0, 45, 90, and 135, then evaluated the clinical, microscopic, and synovial fluid biomarkers in those joints. “No significant difference in joint effusion (swelling) or synovial fluid markers were found between the control and PAAG groups,” she said. “Microscopy showed a layer of the PAAG on the surface of the synovial membrane lining the joint; however, a small amount also integrated into the synovial membrane.”

Together, she explained, these studies showed that the hydrogels neither induced significant inflammation in the joint nor resulted in any negative side effects in healthy equine joints. “The 4% product functions as a viscoelastic supplement, remaining mainly in the joint space, whereas the 2.5% gel integrates into the synovial lining,” said Ortved.

Treating Equine Joint Pathologies with APS

Katie Seabaugh, DVM, Dipl. ACVS, ACVSMR, of the Translational Medical Institute at Colorado State University, in Fort Collins, shared findings from a study coauthored by Ortved, in which

researchers investigated the effects of a single intra-articular (IA) injection of autologous protein solution (APS) in horses with synovitis—inflammation of the synovial membrane.

Ortved and her team studied 18 horses; they injected one tarsocrural (the uppermost hock) joint in 12 horses with APS one day after inducing synovitis. They left six horses untreated as controls.

“While APS did not decrease lameness or joint circumference or alter synovial fluid parameters, gross pathology and histopathology scores were lower for APS treated joints compared untreated (control) joints suggesting that APS may have a disease-modifying effect,” said Seabaugh.

Using NSAIDs With Orthobiologic Treatment in Horses

Seabaugh presented a second study co-authored by Ortved in 2024 in which the research team examined if commonly used nonsteroidal anti-inflammatory drugs (NSAIDs)—either a single intravenous (IV) dose or single oral dose—had any effect on growth factor and cytokine (cell-signaling protein) concentrations in APS and platelet-rich plasma (PRP). Clinicians might use NSAIDs in conjunction with the processing of APS and PRP to reduce pain and inflammation in the horse’s body, especially in cases of injury.

“There was no significant difference in cytokines and growth factors, but NSAIDs were found in the final product,” said Seabaugh. “This means we need to use biologic therapies carefully in athletes that will be drug tested.” More research is needed using long-term NSAID treatment.

Treating Synovial Infections in Horses

Ortved described another study in which de Souza et al. (2024) investigated long-term survival of horses after synovial lavage of contaminated and septic synovial structures. They authors included 240 horses presenting with contaminated or infected synovial structures, including fetlocks, digital flexor tendon sheets, and tarsocrural joints.

She said survival rates were excellent following lavage, with 228 of the 240 (95%) surviving to discharge and 89% alive one year later. Variables associated with not surviving included forelimb involvement, heavier body weight, an unknown cause of sepsis, longer surgery times, and tendon sheath or bursa involvement, said Ortved. However, the researchers did not note a correlation between soundness and survival rate.

Using PET in Sport Horses

Finally, Ortved discussed a study in which authors demonstrated PET imaging, commonly used in racehorses to detect early injury was beneficial for sport horses. The researchers imaged 36 fetlocks using positron emission tomography (PET) and computed tomography (CT) and scored the radionuclide—the tracer practitioners inject before capturing a PET scan—uptake blindly. Thirty-two PET scans revealed a single area of increased radionuclide uptake, most often in the subchondral bone, which is beneath the cartilage. The most common sites were the inner part of the long pastern (medial first phalanx) and the upper inside joint surface of the knee or hock (dorsomedial condyle of the third metacarpal/metatarsal bones). These findings correlated with the CT images and the researchers identified an association with increased radionuclide update on PET scans and pain in the horses.

“PET uptake is common in sport horses, but the pattern of uptake is quite different from racehorses, likely due to differences in biomechanical loading in the joint,” said Ortved. “PET may be very useful in the early identification of bone lesions.”

Take-Home Message

Leading veterinarians chose these six studies due to the impact they had on equine musculoskeletal research in 2024. In this rapid-fire session they shared 2.5% iPAAG, 4% PAAG, and APS might be beneficial in treating horses with joint disease, but case selection is crucial. They also shared research proving veterinarians should be cautious when administering NSAIDs while collecting blood for APS and PRP, but single-dose administration is not likely to affect the final biologic product. In 2024, researchers also showed that synovial lavage might be an effective treatment for synovial infections and PET is an effective diagnostic tool for sport horses.

Many newborn foals need specialized care to address medical challenges that commonly arise during the first weeks of life. During their presentation at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida, two board-certified internal medicine specialists—Laura Javsicas, VMD, Dipl. ACVIM, of Rhinebeck Equine, in New York, and Lisa Edwards, DVM, Dipl. ACVIM, ACVECC, of the University of Florida’s College of Veterinary Medicine, in Gainesville—shared their protocols for treating equine neonatal health issues in the field.

Diarrhea in Newborn Foals

Loose manure in foals can cause important health problems, with severity often varying by age. Neonates under 24 hours old with hemorrhagic diarrhea need immediate attention because this bloody manure can indicate clostridial (a type of bacteria) infection in the abdomen and an increased risk of sepsis (bacteria in the bloodstream). Diarrhea in foals over 2 weeks of age typically concerns practitioners less but still warrants veterinary care.

When managing foals with diarrhea, Javsicas and Edwards generally treat them with a di-tri-octahedral (DTO) smectite for toxin adsorption and intravenous (IV) fluids with dextrose for hydration and nutrition, and they conduct bloodwork to assess electrolyte imbalances, glucose and lactate levels, and renal function. Additionally, performing polymerase chain reaction (PCR) testing on the foal’s manure could help veterinarians identify the infectious agents.

Javsicas and Edwards said veterinarians prefer the antibiotic ceftiofur to treat diarrhea in foals and add metronidazole if they suspect a clostridial infection. The veterinarians added that ultrasound and nasogastric tube (NGT) placement are critical for identifying and relieving any gastric reflux in foals with diarrhea and coliclike signs.

Dehydration and Electrolyte Imbalances in Newborn Foals

Foal diarrhea poses a significant risk of dehydration and can lead to life-threatening electrolyte imbalances, especially hyponatremia (low sodium). For severe dehydration cases veterinarians can turn to a continuous rate infusion (CRI) of IV fluids. Balanced electrolyte solutions are ideal; veterinarians can also add dextrose and sodium bicarbonate (to counteract severe metabolic acidosis) if necessary, Javiscas said.

Both veterinarians recommended closely monitoring foals’ urine output during rehydration as a key indicator of kidney function. They also warned that despite practitioners’ best efforts to manage these cases on the farm, foals with severe electrolyte imbalances or signs of septicemia warrant a hospital referral.

Patent Urachus in Newborn Foals

A patent urachus occurs when the connection between the bladder and umbilical cord fails to close after birth. Veterinarians typically see this condition in foals that spend more time lying down than normal (i.e., “bed babies”), twins, or foals with abnormal or infected umbilical cords. They can treat most cases medically with antibiotics and local wound care, but regular ultrasound monitoring is important to assess the urachus and ensure there are no deeper infections, said Javiscas and Edwards.

Common patent urachus treatments include hypochlorous acid products and povidone-iodine (Betadine), which also have a skin-drying effect that can be beneficial in these cases, Javsicas said. Veterinarians generally only consider surgery if the condition doesn’t improve with medical treatment after 10 to 24 days.

Milk Replacement

Sick foals that cannot nurse need equine-specific milk replacers; Javsicas and Edwards noted that using milk formulated for other species can lead to diarrhea and electrolyte imbalances. If a neonate cannot nurse from its dam, veterinarians might use bottle or NGT feeding as alternatives. But if a foal can’t ingest milk from any source for any significant amount of time, veterinarians should provide IV dextrose supplementation and complete parenteral nutrition.

Take-Home Message

With strategic and resourceful field care, veterinarians can significantly improve outcomes for newborn foals affected by common health issues. Edwards and Javsicas emphasized the importance of thorough diagnostics, timely interventions, and informed treatments to protect neonatal health during this critical stage.

Aging mares play a key role in advancing equine breeding programs, but pituitary pars intermedia dysfunction (PPID), formerly known as equine Cushing’s disease, might interfere with their reproductive performance. Testing broodmares 15 years old and older for this disease and treating when needed might help minimize the negative consequences of PPID on mare fertility, said Sophia Panelli Marchio, DVM, a PhD candidate at Texas A&M University’s College of Veterinary Medicine, in College Station. Marchio spoke about the effects of PPID on mare fertility during her presentation at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida

What is PPID in Horses?

Pituitary pars intermedia dysfunction is a neurodegenerative disease that progresses with age, with worsening clinical signs in older horses. Following stimuli such as stressful events, thyrotropin-releasing hormone, or TRH, stimulates melanotropes—cells that produce melanocyte-stimulating hormone—in the pars intermedia of the pituitary gland to express a gene called pro-opiomelanocortin (POMC). The body then breaks POMC into smaller hormones, including adrenocorticotropin hormone (ACTH). In turn, the horse’s body releases ACTH into circulation where it stimulates the adrenal gland to release a variety of compounds and hormones. 

Dopamine produced by dopaminergic neurons in the hypothalamus inhibits the production of ACTH and other POMC-derived hormones. Thus, horses with neurodegeneration of the dopaminergic neurons lose control over the production of ACTH and other hormones. Often, they overproduce these hormones and, as a result, hyperplastic growth—an abnormal increase in cell number—of the pars intermedia.

Recognizing and Diagnosing PPID in Horses

Classic signs of PPID include polydipsia and polyuria (excessive drinking and urinating), hyperhidrosis (extreme sweating), secondary infections, lethargy, neurologic problems, abnormal fat distribution, hirsutism (a long, shaggy coat due to abnormal shedding), hyperinsulinemia-associated laminitis (HAL), muscle wasting, and a pendulous abdomen.

Veterinarians most commonly diagnose PPID by measuring basal (resting) ACTH levels.

“If evaluating basal ACTH, veterinarians must appreciate that the reference values will change based on season,” said Marchio. “ACTH values can also differ if the animal has been through a stressful situation.”

Effects of PPID on Mare Fertility

In addition to the clinical signs mentioned above, broodmares with PPID might experience an absence of seasonal anestrus, abnormal cycles, anovulatory follicles, subfertility, recurrent endometritis, and abnormal lactation.

“Dopamine plays an important role in controlling reproductive hormones,” said Marchio. “It regulates reproductive seasonality and inhibits cyclicity during the anovulatory season.”

The POMC-derived hormones, including ACTH, increase in mares with PPID. To determine the effect of high ACTH on reproduction, researchers on one study (Hedberg et al., 2007) treated healthy mares with ACTH. “They found a higher concentration of steroid hormones that inhibit gonadotropin-releasing hormone (GnRH) release and an increase in cortisol,” said Marchio. “In turn, high cortisol can repress GnRH as well as luteinizing hormone (LH) release. Further, high follicular fluid cortisol levels can disrupt oocyte quality.” Researchers on another study of healthy mares treated with the synthetic glucocorticoid dexamethasone also reported a reduced LH concentration (Asa et al. 1982).

“Only one study clearly correlates ACTH with impaired reproductive performance (Tsuchiya et al., 2021),” said Marchio. “As ACTH increased, cortisol increased, and mares had lower reproductive success determined by live foaling rates.”

Marchio also said researchers believe the enlargement of the pars intermedia can compress the pars distalis and interfere with the production and release of follicle-stimulating hormone (FSH) and LH, impairing the mare’s cyclicity. They also hypothesize that recurrent endometritis might develop due to the immunosuppressing effects of high cortisol levels.

Treating Broodmares That Have PPID

Administering a dopamine agonist such as pergolide (an FDA-approved dopamine receptor agonist labeled for treating clinical signs of PPID) or cabergoline (another dopamine receptor agonist) and good management practices improve the well-being and reproductive performance of aged broodmares with PPID, said Marchio.

“Be certain to suspend pergolide treatment at least 30 days before foaling and implement the treatment 30 days after foaling as it can interfere with lactation,” she added.

Take-Home Message

Formerly known as equine Cushing’s disease, PPID in horses might have negative effects on mare fertility. “We only have hypotheses on how PPID affects reductive performance,” said Marchio. “The exact mechanisms are still unknown and must be studied in depth utilizing horses with PPID.”

Equine herpesvirus-1 (EHV-1), a significant cause of respiratory and neurological disease in horses, can spread stealthily at equestrian events, often going unnoticed. Nicola Pusterla, DVM, PhD, Dipl. ACVIM, AVDC-Equine, professor of equine internal medicine and epidemiology at the University of California, Davis, School of Veterinary Medicine, recently led research on the role that subclinical shedders—those that do not show signs of infection—play in spreading the virus. He presented his findings at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida, and raised concerns about current practices for detecting and managing EHV-1.

Silent Shedding and EHV-1 Environmental Spread

Horses that appear clinically healthy might still shed EHV-1 and contribute to outbreaks, complicating efforts to prevent viral spread. Pusterla’s research team tested 162 apparently healthy horses at a California horse show in April 2022. While only three (1.85%) horses tested positive for EHV-1 using quantitative PCR (qPCR), testing environmental samples from stalls revealed more positive results.

Immediately after the event the researchers collected sponges (specifically used to collect samples) from stalls and identified, among others, five EHV-1-positive stalls in one barn. “This clustering pattern confirms that the respiratory virus can easily spread among horses sharing close quarters and suggests that transmission might occur more subtly than we previously understood,” Pusterla said.

Focusing on EHV-1 Environmental Detection

The research team conducted a second study to evaluate the accuracy of environmental sampling in detecting EHV-1. They collected samples daily for 11 days using nasal swabs, stall sponges, air samples, and stall strips in an eight-stall barn housing seven adult horses aged 5 to 16 years old. Four horses had been vaccinated with a modified-live intranasal EHV-1 vaccine to mimic subclinical shedding; the remaining three horses were unvaccinated.

All intranasally vaccinated horses shed EHV-1 in nasal secretions at levels and for a duration similar to what is expected in subclinical shedders, while none of the controls had detectable EHV-1 in nasal secretions (the EHV-1 vaccine strain is harmless and cannot be transmitted to other horses, hence it does not contribute to the spread of EHV-1). The team used sponges to detect EHV-1 in the stalls of all vaccinated and one control horse. With stationary strips they detected EHV-1 in the stalls of three of four vaccinated horses but none of the controls. Air samples showed low detection rates, likely due to low concentrations of aerosolized EHV-1.

“The highest detection rates came from stall sponges, particularly in feeding areas where droplet contamination from nasal secretions is likely,” Pusterla said. The researchers established that the virus did not necessarily transfer directly between horses but did accumulate in shared and high-traffic spaces such as stall walls and water buckets.

Implications for Biosecurity at Equine Events

Pusterla’s research highlights the importance of implementing biosecurity measures to control EHV-1 at horse shows. He reported that traditional diagnostic methods, such as nasal swabs, are invasive and might miss shedding. Environmental sampling, particularly with stall sponges, could offer a more effective and practical approach to identifying viral clusters and taking preventive measures. However, the study’s limitations include a small sample size and no assessment of viral viability in the environment.

Take-Home Message

Pusterla emphasized the need for vigilant monitoring and proactive strategies to mitigate EHV-1 risks. Farm owners and managers should prioritize good biosecurity practices with their hygiene and cleaning efforts, especially in areas prone to droplet contamination, such as feeding zones and high-traffic areas. Equally important, environmental testing could be a vital tool for early detection and prevention of outbreaks, helping limit the silent spread of EHV-1.

During her career, Lisa Fortier, DVM, PhD, Dipl. ACVS, James Law professor of surgery at Cornell University’s College of Veterinary Medicine, in Ithaca, New York and editor of the American Veterinary Medical Association’s journals, has made, and continues to make, contributions to developing and revolutionizing orthobiologics in equine medicine. In this field, practitioners use treatments derived from biological substances, such as stem cells, to manage musculoskeletal conditions.

Fortier presented her research on the history and future of orthobiologics, providing key takeaways for veterinarians using these therapies, during her Frank J. Milne State-of-the-Art Lecture at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida. She described the history of the main orthobiologics used today in equine practice: autologous conditioned serum (ACS), which concentrates platelets and interleukin-1 receptor antagonist protein, or IRAP; platelet-rich plasma (PRP); autologous protein solution (APS); and bone-marrow-derived cultured mesenchymal stem cells.

Which Orthobiologics Are Best for Horses?

“The main questions I get asked about orthobiologics are: ‘Which one is best?’” said Fortier. “‘How many injections should I perform?’ And, ‘When can we get the horse back to work?’” But, despite dedicating her life’s work to studying orthobiologics and implementing these in her practice, she said she’s learned these biologics are complex and there are still no clear answers to these questions. “There are a lot of different cells in play, and they change from horse to horse,” Fortier said. “None of the biologics are miracle drugs, but I still recommend orthobiologics as first-, not last-line, therapies.”

Fortier emphasized the importance of using orthobiologics to treat acute joint injuries involving an abundance of the pro-inflammatory mediator interleukin (IL)-1 . For example, Fortier recommended administering ACS at the time of injury, then following up with either additional ACS treatments or a 2.5% polyacrylamide hydrogel.

Platelet-Rich Plasma for Soft Tissue Injuries and Equine Joint Health

Veterinarians primarily use PRP in tendon and ligament injuries in horses, although physicians typically use the approach for treating joints in human medicine. “There is no scientific reason for this, it’s just the way it evolved,” Fortier said.

Veterinarians have not developed a true definition for what constitutes PRP, but they typically believe PRP contains five times more platelets than blood. The growth factors contained in those platelets are considered the active ingredient.

One of the key advances in PRP was discovering the need for leukoreduced PRP. “Leukocytes, also known as white blood cells, and one particular population of leukocytes, called neutrophils, are lightly inflammatory,” said Fortier. “When treating a musculoskeletal injury, we don’t need further inflammation, so using a leukoreduced PRP is advisable.”

When using PRP in practice, Fortier said she delivers it using ultrasound guidance, being careful not to overfill the lesion. She collects bone marrow during the same visit in case she wants to use stem cells moving forward because the stem cell culture process takes about eight weeks to complete.

Fortier also recommends using shock wave or pulsed electromagnetic field (PEMF) therapy for soft-tissue injuries. If she sees no response (i.e., 50% improvement in lameness), she reevaluates her diagnosis rather than simply repeating the PRP injection. If she does note a response, she’ll repeat the PRP injection in two weeks. A third injection is rarely in her repertoire. Instead, she’ll use the cultured stem cells or a 2.5% polyacrylamide hydrogel.

Autologous protein solution (APS) is an alternative to ACS (IRAP) and PRP, providing a patient-side means of delivering IL-1Ra and growth factors. This orthobiologic is produced from a patient’s blood sample incubated with special beads that stimulate cytokines and chemokines in 20 minutes (rather than overnight). APS has a much lower concentration of IL-1Ra than ACS (and both have more IL-1Ra than PRP) and yields a smaller volume. 

Bone Marrow and MSCs for Equine Injury and Joint Health

Fortier said bone marrow concentrate products fulfill the requisite trilogy for tissue repair: stem cells, cytokines (proteins that help regulate inflammation), and a scaffold that provides structural support for tissue development.

One of the key messages Fortier shared was the importance of using autologous products—biologics collected from the patients themselves. “Allogeneic cells, from another horse, induce an immune response, and that response can be massive following a second injection, possibly resulting in the loss of the horse,” said Fortier.

What Horses are Good Candidates for Biologics Treatment?

Regardless of which orthobiologics a veterinarian chooses, Fortier stressed the importance of starting with a systemically healthy horse.

“Nothing is going to heal if you have bad biology,” she said. “We’re becoming much more aware of subtle endocrine abnormalities, and these horses, who have a higher risk of tendon injury, will not heal as you might expect.” For this reason, Fortier recommends routine endocrine testing of all horses as part of their wellness program.

Take-Home Message

Veterinarians should examine horses’ overall health before considering them as candidates for orthobiologic treatment. The approaches veterinarians choose vary depending on each patient’s injury, disease, and health status, but they should treat a horse in the acute injury phase to increase the likelihood of success.

Mean glandular severity scores were significantly lower in the treatment group on Days 28 (shown) and 35, as seen on gastroscopy exam. | Courtesy Dr. Frank Andrews

Equine gastric ulcer syndrome (EGUS) refers to any ulceration inside a horse’s stomach. It often causes severe physical pain, leading to clinical signs such as behavior changes, weight loss, and loss of appetite.

Veterinarians view omeprazole as the mainstay EGUS treatment, said Frank Andrews, DVM, MS, Dipl. ACVIM, LVMA equine committee professor of equine medicine and director of equine health and sports performance at Louisiana State University’s School of Veterinary Medicine, in Baton Rouge. He spoke on the subject at the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida. But because omeprazole might not be suited for long-term use, he said he and his team studied a schizophyllan—a beta-glucan—and hyaluronan product (relyneGI) to see if it could be useful in caring for ulcery horses.

Schizophyllan and Hyaluronan

Hyaluronan is a high-molecular-weight glycosaminoglycan in joint, intestinal, and gastric tissues. “It functions to maintain gastric and intestinal homeostasis, innate immunity, and modulates inflammation,” said Andrews. “In rats—which have a similar stomach to a horse with a squamous and glandular region—hyaluronan has been proven to protect the gastric lining and improve gastric mucosa integrity.”

Beta-glucans are an integral part of cell walls; schizophyllan activates immune cell maturation, differentiation, and proliferation. They have prebiotic properties and have been proven safe for use in horses.

Andrews and his team studied the efficacy of the new schizophyllan and hyaluronan gastric support supplement in 12 stall-confined Thoroughbred and Thoroughbred-cross horses with naturally occurring gastric ulcers. They divided horses evenly into treatment and control groups, performed gastroscopic exams, and weighed each horse at the start of the study after two days of acclimatization.

Over the 35-day treatment period the team gave 1 ounce (the high-stress dose) of the supplement three times daily in each treatment group horse’s feed and a 1-ounce dose of placebo three times daily in each control horse’s feed. They were blinded to treatments to avoid bias in scoring and repeated gastroscopies and weight checks on Days 14, 28, and 35.

Supplement Effects on Gastric Ulcer Scores

Andrews and his team saw a significant weight increase in all horses, but the treatment did not affect body weight. The mean nonglandular EGUS and severity scores were significantly lower in the treatment group on Days 28 and 35.

“The nonglandular ulcers were healed, except for mild hyperkeratosis (callousing), on these dates as well,” Andrews said. “The mean glandular (ulcer) and severity scores were significantly lower after 14 days in the treatment group. The ulcers did heal, but some reoccurred in both groups of horses by Day 28, which is not uncommon in these types of ulcers.” The mean gastric fluid pH remained low and variable throughout the study in both groups. Many drugs when used long term block gastric acid, which can change the stomach’s physiology. In other words, this supplement contributed to gastric health without changing stomach acidity.

Take-Home Message

Based on the research, Andrews said he believes the schizophyllan and hyaluronan supplement might have uses for managing horses with EGUS long-term and/or in conjunction with appropriate pharmaceutical treatment. (Supplements shouldn’t be used to treat disease but improve stomach health after discontinuing pharmacologic agents, he added.) The researchers observed clear improvement in nonglandular and glandular ulcer scores in the treatment group and did not observe any adverse effects from the supplement. The horses also readily consumed it, he added.

Andrews noted study limitations were a small sample size with limited breeds, a short treatment period, and that horses were stalled without exercise—management approaches that can be risk factors for ulcers. He hopes to address these limitations in future studies by finding out if the schizophyllan and hyaluronan product acts synergistically (a combined positive effect) with omeprazole or other drugs to improve gastric health in horses as well as prevent gastric ulcer recurrence.

By Amy Rucker, DVM, with Megan McCracken, DVM, Dipl. ACVS

The navicular bone—also known as the distal ­sesamoid—is located within the foot and acts as a fulcrum, altering the angle of the deep digital flexor tendon (DDFT) just proximal to (above) its insertion on the bottom of the coffin bone (third phalanx). Thirty years ago we attributed any heel pain lameness to “navicular syndrome.” Now, with better imaging techniques, we can identify and treat a multitude of navicular-associated issues that fall under the term podotrochlosis, often before bony changes are visible on radiographs (X rays). Injuries can occur to the DDFT, the navicular bone, or a variety of other soft tissue structures within the hoof capsule. How we treat the lameness depends on the information we obtain with our history, physical exam, and imaging findings.

The horse’s history of lameness might vary depending on his stage in the disease process. Acute lameness might be evident in one foot. If the pathology is advanced, the horse might exhibit a shortened stride with both front feet while trotting straight, with inside-leg lameness evident while turning either direction. My favorite way to observe a possible navicular horse is to have the owner trot the horse in hand in a tear-drop shape on sloped ground. The horse might be sound trotting away, then be lame as it turns on the uneven ground. Often a navicular horse is not positive to flexion of the distal limb (fetlock/pastern/coffin joint).

When I look at a foot, I think about what part of it is carrying the heaviest load or has the most force placed upon it. I evaluate the angle of the foot and pastern, the length of the toe and heel, sole depth, the strength of the frog and heel bulbs, whether the horse’s conformation predisposes crushing of the medial (inside) or lateral (outside) heel. Some veterinarians use hoof testers to evaluate for pain, but I find those unreliable due to variations in hoof mass and dryness. I palpate the foot and note excessive fluid/effusion of the coffin joint at the coronary band or DDFT sheath above the heels or thickening of the tendons and ligaments in the pastern area. After examining a horse and watching it in motion, we “block” the lameness out by temporarily anesthetizing local nerves or joints. Most navicular cases improve with a palmar digital nerve block, anesthetizing the heel and sole region. Some require a low ring block to anesthetize the entire navicular apparatus. When the injured area is no longer painful, the horse moves sound, and we know which area of the leg is causing pain, we move to imaging it with radiographs.

Beau, a Tricky Case With a Positive Outcome

Beau was an 8-year-old Quarter Horse gelding purchased for a novice rider as a proven Western performance horse. He was advertised on the internet and had a successful show career with consistent recent competitions. The trainer and rider traveled across several states to try Beau, fell in love with him, and had a prepurchase examination done, where he was deemed sound on physical exam and radiographs. Some of the X ray views offered limited information due to positioning of the foot and amount of exposure and clarity. However, Beau lived in an area without an option for a second opinion exam, so the buyer completed the purchase. 

Beau arrived sound and stayed sound for months before an intermittent left front lameness developed. Initially, the trainer would notice a subtle lameness, but Beau would be sound by the time I performed an exam the next day.  Eventually, I localized the subtle lameness to the foot via nerve blocks and injected the coffin joint with hyaluronic acid and triamcinolone. (These two drugs have different mechanisms to reduce synovitis, or joint inflammation. We also know the steroid triamcinolone will diffuse from the coffin joint into the navicular bursa—the small fluid-filled structure that pads the navicular bone so the DDFT can move over it smoothly.)

Beau’s lameness resolved after treatment, but only for several weeks. When the lameness returned I referred Beau to a hospital for diagnostic imaging. A palmar digital nerve block resolved his consistent left front lameness, and radiographs revealed bony changes of the navicular bone.

At this point, financial limitations would send most horse owners home with recommendations for shoeing changes and other general treatments and a plan to return to work in a couple of weeks if sound. Sometimes, however, we can look beyond the radiographic navicular bone changes and determine whether the acute lameness is due to a different issue, such as a collateral ligament injury to the coffin joint. In this case we performed an MRI on Beau to further evaluate the foot, which allowed us to tailor treatment to his specific issues.

Magnetic resonance imaging enables us to gain additional valuable information about bone and soft tissue. Beau’s MRI showed some of the navicular bone changes visible on the radiographs in more detail. The radiographs had identified a cystic lesion in the navicular bone, and the MRI revealed the lesion was a full-thickness flexor cortex erosion. The scan showed evidence of fluid or edema within the navicular bone, indicating more active or acute injury. The MRI also enabled us to carefully evaluate the soft tissue structures within the foot. Many of these critical structures cannot be visualized with ultrasound, so MRI is often the only way to identify injury. It is especially useful and critical when radiographs are normal because it allows interventions early in the podotrochlosis case.

In Beau’s case we found a core lesion, or central tear, in the medial lobe of the DDFT, as well as fibrillation, or roughening, of the tendon surface. We also saw evidence of inflammation in the navicular bursa (bursitis). The changes to Beau’s navicular bone appeared chronic and probably predated his recent lameness episode. The soft tissue injuries are the likely source of the more acute lameness. As we gain more information about the navicular region, we realize how complicated and interconnected the bone and soft tissue structures are here. With Beau, the roughening of the flexor surface of the navicular bone caused by the chronic erosion likely contributed to his DDFT injury.

These structures’ complicated interplay highlights the need for careful coordination between veterinarian and farrier. As a result of the MRI, we were able to develop a detailed treatment plan tailored to Beau’s injuries. He was started on a rest and rehabilitation program to enable healing of the DDFT injury. This included stall rest and hand-walking. Initially, the hand-walking was only on firm ground. Gradually, we introduced walking in an arena with 6 inches of noncompacted footing. The program slowly progressed to riding at the walk, small paddock turnout, slow introduction of trot work, and a gradual return to full work and turnout. During the months of recovery, the ground conditions were strictly controlled: Beau was never exercised or turned out in uneven or deep footing.

When treating soft tissue injuries it is important to give them time to heal and to increase work gradually to encourage the greatest strength in healing. Avoiding sudden exaggerated movements that might cause re-injury is critical. In addition to the rest and rehabilitation plan, we treated the inflammation in Beau’s navicular bursas with triamcinolone injections. Beau also received bisphosphonate injections. Bisphosphonates have been shown to increase comfort in horses with osseous changes to their navicular bones by inhibiting bone breakdown and resorption.

We also devised a podiatry plan to reduce breakover and tension on the DDFT. Consistent, careful farrier work is critical to success with these patients. Typically, horses with flexor cortical erosions tend to have poor prognoses for return to work and prolonged soundness. But due to the diligent care of his owners, veterinary team, and farrier, Beau returned to performance. If this plan had not led to Beau returning to soundness or if he re-injured himself, we could have pursued additional treatment options. These include navicular bursoscopy, where we use a small camera and instruments to visualize the navicular bursa and remove proliferative synovium, fibrous tissue, and any adhesions that might be present. Another option would be injecting the DDFT lesion directly with platelet-rich plasma or stem cells—either in conjunction with a navicular bursoscopy or with MRI guidance.

Take-Home Message

As veterinarians we do the best we can with radiographs, but MRI provides a more accurate look at pathology, including bone inflammation (not just the bone remodeling evident on X rays). Beau likely came to us with the navicular cortex lesion in his left front and was able to perform until he developed associated lesions in the DDFT and navicular bursa. (Beau’s right front foot had similar bony changes but no soft tissue lesions, and he remained sound on that foot.) 

Beau’s MRI dictated a six-month rehabilitation program in a controlled environment. Unfortunately, many horses with Beau’s initial exam findings and radiographs have their coffin joints and/or navicular bursas injected with medications and return to work when sound (or are turned out in paddocks or pasture with uneven footing), and activity creates further injury. My goal with horses is to maximize their ability to work for a lifetime. In Beau’s case we have made every effort to heal his acute lesions and returned him to work at a lower level.

Beau is still ridden in performance classes but is no longer doing cattle work because we question his ability to stay sound with sudden changes in speed and direction. “Finished,” show-ready 8-year-old horses that can be ridden by an amateur usually come with some orthopedic baggage. I hope our team approach allows Beau and his baggage to continue their journey with a happy owner for years to come.

RNA vaccines were tremendously successful during the Covid-19 pandemic due to excellent stimulation of immune responses combined with a fast and easy production process.

Traditional vaccines are typically based on subunit, inactivated or attenuated pathogens, which require long development times, making a rapid response to newly emerging pathogens difficult. In contrast, the RNA in RNA vaccines encodes the primary immunogenic protein(s) of the pathogen and can be developed quickly once the genetic sequence of a pathogen is known. This RNA is formulated or ‘packaged’ in lipid nanoparticles, cationic polymers, or hyperbranched polyglycerol (hPG) amines to allow for efficient transfer into host cells where the RNA of interest is translated into an immunogenic protein.

This protein then triggers an immune response against the very same protein expressed by the pathogen. Currently, RNA vaccines are being explored for a wide range of human and animal pathogens. The main advantages of RNA vaccines are that the production of RNA vaccines is technically simple, fast, easy-to-adapt, cost-effective and free of animal material.

There are currently two types of RNA vaccines, the conventional mRNA vaccine and self-amplifying (sa)RNA vaccines. The conventional formula contains a fixed concentration of packaged mRNA while saRNA vaccines may contain less target RNA than the conventional formula, but in addition contain a sequence encoding for an enzyme called ‘replicase,’ which amplifies the RNA sequence of interest, (i.e., itself). The advantage is a ‘smaller’ package with a longer duration of protein expression depending on the replicase half-life.

While vaccines for some pathogens are easy to design because there is only one, or few, immunologically important protein(s) for protection, other pathogens are more complex and require a multiple-target or cascade approach. This is one of the biggest limitations of RNA vaccines, as only a limited number of RNA sequences of interest – up to three – can be packaged into a single product or injection. Another disadvantage of RNA vaccines is storage, as most require storage at either -20°C or even at -80°C.

Equid alphaherpesvirus 1 (EHV-1) and 4 (EHV-4) are common equine viral pathogens. Horses in North America are routinely vaccinated against several viruses, including Western and Eastern Equine Encephalitis virus (WEEV, EEEV) and against West Nile virus, as well as equine influenza virus (EIV), with all of these vaccines performing reasonably well. In contrast, EHV-1 and EHV-4 outbreaks still occur in well-vaccinated populations. Thus, it is not surprising that the first efficacious nucleic acid vaccines have been developed against viruses for which protective immune responses can be induced with one (or few) immunogenic proteins, including coronavirus, flaviviruses and influenza viruses.

Unfortunately, EHV-1 and EHV-4 are not one of these viruses. Currently, challenges of developing effective mRNA or saRNA vaccines against equine herpes viral infections include the inherent antigenic complexity and immunosuppressive functions of EHV-1 and -4. With funding available through the Grayson Jockey Club Equine Research Foundation in Lexington, Kentucky, and in collaboration with Paul Lunn, BVSc, MS, PhD, MRCVS, Dipl. ACVIM, dean of the University of Liverpool’s School of Veterinary Science, in the U.K., and Juergen Richt, DVM, PhD, Director of Kansas State University’s Center of Excellence for Emerging and Zoonotic Animal Diseases (CEEZAD) and NIH COBRE Center on Emerging and Zoonotic Infectious Diseases (CEZID), in Manhattan, we are currently testing the safety and efficacy of EHV-1 mRNA and saRNA vaccines.

Based on previous experience, our vaccine prospects include nucleic acid sequences encoding EHV-1 glycoprotein D and the Immediate Early (IE) gene. The rationale is based on available results from previous studies with EHV-1, and ii) on the Shingrix® vaccine success story of a subunit vaccine that only contains the glycoprotein (g)E (analogous to EHV-1 gD) preventing shingles in adults after childhood varicella-zoster infection (chickenpox).

We expect these two components to be highly immunogenic, and to stimulate both cellular and humoral (antibodies) immunity. This project is ongoing, and we will provide updates on the progress. We anticipate that testing the vaccine in a neurological model of EHV-1 will show at least some protection from EHM which will be an improvement over currently available vaccines. In the future, this strategy can be further refined and tested for duration of immunity or effectiveness as a booster following vaccination with conventional vaccines. Because of the high sequence homology of the selected viral proteins, it is likely that this vaccine would also offer cross protection to EHV-4. Finally, once we can show the applicability of the technology for EHV-1 in horses, it could readily be adapted to other viral pathogens of horses.

Editor’s note: This is an excerpt from Equine Disease Quarterly, Vol. 34, Issue 1, funded by underwriters at Lloyd’s, London, brokers, and their Kentucky agents. It was written by Lutz S. Goehring, DVM, MS, PhD, Wright – Markey Professor of equine infectious diseases at the University of Kentucky’s Gluck Equine Research Center, in Lexington, Gisela Soboll Hussey, DVM, PhD, professor at Michigan State University’s College of Veterinary Medicine, in East Lansing, and Klaus Osterrieder, Dipl. ECVM, dean of City University’s Jockey Club College of Veterinary Medicine and Life Sciences in Hong Kong, professor of virology and chair at Freie Universität, in Berlin, Germany, and adjunct professor of virology at Cornell University, in Ithaca, New York.