Researchers have determined supplementing horses’ diets with protein within a short but safe timeframe after exercise might help them build muscle mass more than providing the same supplement at regular mealtimes.

A high-protein snack—given as soon as the horse is resting again—could add critical amino acids to the bloodstream when muscles need them for repair and damage control, said Patty Graham-Thiers, PhD, professor and department head of the equine studies program at Emory & Henry University, in Virginia.

In a previous study Graham-Thiers and her colleagues found that supplementing young and even senior horses’ diets with amino acids helped improved their muscle mass—which horses naturally lose with advancing age. It made her wonder whether the supplements might be even more useful if they’re provided right when the body needs them most, shortly after exercise.

“In humans it’s common to consume protein post-exercise to help with muscle mass recovery and development, especially in body builders,” she said. “So, I thought, what if amino acids are delivered (to horses) after exercise when the body is recovering and needs amino acids, either for repair or development of muscle tissue?”

Feeding Horses a High-Protein Supplement After Exercise

To find out, Graham-Thiers and Kristen Bowen, BA, an equine exercise and nutrition research assistant at Emory & Henry, tested the effects of supplementation timing on eight healthy adult riding school horses. The horses participated in light to moderate maintenance exercise one to two hours per day, five days per week for 12 weeks.

Caregivers provided all the horses morning and evening meals consisting of grass hay, textured feed, and corn. In addition, the animals consumed a daily high-protein pellet made of 32% crude protein.

Half the horses received the protein supplement split into their two daily meals, while the other half received the supplement about 20 minutes after exercise—once their heart rates, breathing, and body temperatures dropped to regular resting levels. On rest days without exercise, these four horses ate their protein pellets as a separate midday snack.

The team collected urine and feces from each horse for four days before and after the 12-week experiment. They also took blood samples at the start and end of the study period, which they drew immediately after exercise and one and three hours later.

Studying the Effects of Feeding Timing on Muscle Health

The researchers used the urine and fecal samples to calculate nitrogen balance. Blood plasma samples allowed them to measure amino acid concentrations, albumin, plasma urea N (PUN), creatine kinase (CK), and creatinine.

The results of these tests revealed horses receiving supplementation in their meals had higher plasma concentrations of amino acids than those receiving the supplement shortly after exercise. The researchers explained this is likely because the horses had consumed more protein before exercise than the others, which had not yet had their daily protein pellets.  

The horses receiving the supplement after exercise had rising amino acid concentrations at the one-hour and three-hour post-exercise readings—likely reflecting a beneficial amino acid pool, the team said. The other horses’ amino acid concentrations, meanwhile, dropped.

Additionally, horses receiving the supplement just after exercise retained nitrogen better, which suggests they might have a timelier supply of proteins and amino acids for muscle protein repair and development.

The post-exercise supplementation group also had higher creatinine levels (a known marker of muscle mass) in their plasma. And they had less creatine kinase—an indicator of muscle protein damage or breakdown. This suggests horses might have been recovering faster after exercise than the other group, the researchers said.

Combined, the findings suggest feeding horses a high-protein meal shortly after exercise could help boost levels of circulating amino acids, which could aid muscle protein development while protecting against muscle protein breakdown.Even so, Graham-Thiers said more research is necessary before she and her colleagues can offer concrete supplementation guidelines.

Take-Home Message

“Ideally, I would suggest providing a small high-protein meal when it is safe to do so after exercise,” she noted. “However, this is not always practical. I would encourage riders to be aware of the time frame between feeding and exercise; the longer that time has been, the more important it might be for recovery to offer a small high-protein meal after exercise.”

The study, ”Timing of feeding a protein supplement on nitrogen balance and plasma amino acids during exercise recovery in horses,” appeared in the Journal of Animal Physiology and Animal Nutrition in July 2024.

On May 30, a 14-year-old mare at a boarding facility in Seminole County, Florida, tested positive for strangles. The horse developed clinical signs on April 11, including fever and nasal discharge. She is now recovering. 

In addition to the confirmed case, four horses are suspected positive, and 30 horses are exposed. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

A recent cluster of equine infectious anemia (EIA) cases has once again highlighted the importance of proper training of the individuals that work in equine veterinary clinics to help prevent the spread of disease via iatrogenic (relating to illness caused by medical examination or treatment) transmission.

A cluster of EIA-positives that were infected throughout May 2024 and another cluster from mid-June through the end of August 2024 were found to have originated at a Texas equine clinic. All the EIA-infected horses had been hospitalized in the intensive care unit (ICU) at the clinic and had an intravenous (IV) catheter placed and flushed.

As of May 30, 2025, the USDA Animal and Plant Health Inspection Service (USDA-APHIS) has identified 21 horses confirmed positive for EIA in four states—California, Colorado, Oklahoma, and Texas. The affected horses are of varying ages, breeds, and disciplines.

“I don’t believe we have found all of the exposed horses for testing just yet,” said Angela Pelzel-McCluskey, DVM, USDA-APHIS equine epidemiologist. “I think there are more that need to be added to the list.” She added that anyone who is concerned  their horse might have been exposed should contact their veterinarian and have their horse(s) tested.

The incubation period of horses infected with EIA is usually 15 to 45 days, and horses that have been infected with the virus are lifelong carriers. Horses showing clinical signs of the disease are more of a threat to healthy populations because of higher levels of the virus circulating in the blood.

Horses that survive the initial clinical phase of the disease usually become outwardly inapparent carriers and remain a lifelong reservoir for the disease. There is no treatment for the disease and no vaccine to prevent an EIA virus infection. If confirmed positive, horses are usually euthanized to prevent ongoing transmission to other horses. If not euthanized, horses must be permanently quarantined with separation from noninfected horses by at least 200 yards to prevent spread of the disease by biting flies. Infected horses cannot be moved from quarantined premises except by approval of state and federal animal health officials. Clinical signs of EIA might include fever, depression, low platelet count, anemia, red or purple spots on the mucous membranes, edema, muscle weakness, and atrophy, although chronically infected horses often show no obvious clinical signs of the disease.

Veterinarians diagnose EIA by testing antibody levels in the blood. They most commonly use the Coggins test, which is an agar gel immunodiffusion (AGID) test. An ELISA (enzyme-linked immunosorbent assay) test is also available to detect EIA antibodies. Practitioners must collect blood and submit it to certified laboratories for testing.

The USDA-APHIS has reviewed the complete medical history of the 21 horses confirmed EIA positive that were treated at the Texas clinic.

The current investigation indicated at least one or more employees of the clinic were reusing needles or syringes to draw up and flush IV catheters with heparinized saline in the ICU as a routine procedure, which caused repeated instances of blood contamination into the bottles. “The original sources of the EIA virus were likely bush-track or other high-risk horses that were admitted to the clinic ICU just prior to each cluster of cases in May and August,” said Pelzel-McCluskey.

The USDA-APHIS began investigating the cases in September 2024, when a 3-year-old Quarter Horse mare in Wise County, Texas, was confirmed EIA-positive. The horse was used for barrel racing and had no flat-track racing history, and her cohorts were EIA negative. Another Wise County case, an 8-year-old Andalusian mare with no racing or import history and with all negative cohorts, was found EIA-positive the following month. The next two months brought three more cases from the same county. The horses showed no common EIA risk factors and had no contact with each other.

“The only thing we could come up with is that all of the horses were seen by the same veterinary clinic,” Pelzel-McCluskey said. “That for a small county area is not strange, so it was a head scratcher.” She noted the horses home premises were not located adjacent to each other, so it was not a local geographic focus of natural fly-bite transmission.

Through investigation, officials determined the only common factor was that the horses had been hospitalized in either two clusters May 2024 and August 2024; three horses in May and two in August for other reasons and EIA was not diagnosed.

At the request of the USDA-APHIS, the horse owners began sharing medical records of the five infected horses. At the same time, four more cases with connections to the same veterinary clinic were discovered in January, February, and March of this year—two more horses from Wise County, one from Denton County, and one located in Oklahoma.

Pelzel-McCluskey said the next step in the investigation is to compile a more complete list of exposed horses from the clinic’s appointment book to identify horses that had an IV catheter placed at the clinic during the affected time range, while completing regulatory EIA testing of all horses that were potentially exposed. Testing will also be completed on cohorts of any new EIA-positive cases.

About 1.3 million horses per year are tested for EIA. So far in 2025 there have been 44 EIA positives. In 2024 there were 147 positive cases, and 120 of those were in the primary high-risk category of Quarter Horse racehorses that contracted the disease via iatrogenic transmission by unhygienic injection practices of owners and trainers, not veterinarians.

The rate of EIA positives has been on the rise since 2016 when there were only 44 cases recorded, with the majority being natural transmission via fly bites. The iatrogenic-transmission EIA cases now being found in Quarter Horse racehorses frequently have ties to unsanctioned or bush track racing.

“I believe that veterinary clinic owners and employees have become complacent, and people don’t believe that something like this could happen, but it does happen, and it is happening at a very large scale with a lot of negative outcomes,” Pelzel-McCluskey said. “I would like state animal health officials to reach out to remind people that we do have iatrogenic transmission of EIA, and this can occur in clinics if the expected procedures for sterile technique are not being followed by all employees at the clinic.”

By Leslie Barlow and Dr. Angela Pelzel-McCluskey for the Equine Disease Communication Center (EDCC)

With hurricane season upon us, horse owners must take proactive measures to ensure the safety and well-being of their animals. Here are some tips from the Louisiana State Animal Response Team (LSART), the Louisiana Department of Agriculture and Forestry, and the LSU School of Veterinary Medicine for horse owners to effectively prepare in areas prone to hurricane damage: 

Family Preparedness

Develop a personal plan with provisions for your entire family, including your animals, and update the plan yearly. Saving the Whole Family is a useful guide from the American Veterinary Medical Association (AVMA). 

Health and Identification

• Ensure your horse is up to date on his/her vaccinations against rabies, tetanus, and the encephalitis viruses (Eastern and Western equine encephalomyelitis, and West Nile virus).
• Establish a network and communication plan with the horse and farm animal-owning neighbors in your parish (or county, depending on where you live). Get to know one another, hold meetings to discuss various scenarios, and identify local resources for handling disaster situations. Be prepared to assist one another.
• Familiarize yourself with your parish (or county) emergency managers, who are responsible during emergencies. If you are a Louisiana resident visit gohsep.la.gov/ABOUT/STATE-REGIONS for specific contact information.
• Be sure your horse has two forms of identification: (1) Permanent identification such as a microchip, tattoo, or brand, and (2) A luggage-type tag secured to the tail and halter (be sure to use a leather halter for breakaway purposes). Fetlock tags are useful and can be acquired online or from a local farm supply store, or you can use a paint stick or nontoxic spray paint. Clearly legible tags should include your name, address, and phone number (preferably someone out of state in case of local phone outages).
• Keep a record of the microchip number (perhaps on your Coggins, which is your annual proof of a negative test for equine infectious anemia, or EIA) in an easily accessible location. It is advisable to keep a duplicate copy with a family member or friend in a distant location for safekeeping.

Evacuation Planning

• Always plan to evacuate if possible. Identify a destination and predetermine the routes well in advance. It is crucial to relocate your horses a sufficient distance from the coast—if you’re a Louisiana resident, that is preferably north of Interstate 10 and ideally north of Alexandria. Aim to evacuate at least 72 hours before the anticipated storm arrival. Avoid the risk of being stuck in traffic with a trailer full of horses and a looming hurricane. Share your evacuation contact information with your neighbors.

Emergency Preparedness

• Prepare a waterproof emergency animal care kit with all the items you normally use, including medications, salves or ointments, cohesive bandage (Vetrap or CoFlex), other bandages, tape, etc. Store the kit in a safe place where you can easily access it following a storm.
• Initiate early property cleanup to remove debris that could be tossed around by strong winds. Be careful of down live power lines that can pose a danger to people and animals.

Sheltering at Home

• The choice of keeping your horse in a barn or an open field is up to you. Use common sense, taking into consideration barn structure, trees, power lines, condition of surrounding properties, and the likelihood of the property and structure to flood. Farms subject to storm surge or flash flooding should turn their horses out so horses are less likely to get trapped and drown.
• Remove all items from the barn aisle and walls and store them in a safe place.
• Have at least a two-to-three-week supply of hay (wrapped in plastic or waterproof tarp) and feed (stored in plastic watertight containers, securing the container seams with duct tape). Place these supplies out of reach of floodwaters in the highest and driest area possible.
• Fill clean plastic garbage cans with water, secure the tops, and place them in the barn for use after the storm.
• Place an emergency barn kit containing a chain saw and fuel, hammer(s), saw, nails, screws, and fencing materials in a secure area before the storm hits so that it is easily accessible following the storm.
• Have an ample supply of flashlights and batteries and other nonperishable items.

Communications and Up-to-Date Information

• Listen to local radio stations in your area. If you have internet access, visit state-run websites that provide accurate status information (i.e., State Police, State University, Louisiana Department of Agriculture and Forestry) and take all cautions/warning serious and act accordingly.
• Visit the LSART website for more detailed information regarding horse hurricane preparations and other emergency and health-related information.  

If you’re a Louisiana resident and your animals need emergency medical care after hours, the LSU Veterinary Teaching Hospital on Skip Bertman Drive is available 24/7, 365 days a year. For pets and small exotics, call 225/578-9600, and for horses and farm animals, call 225/578-9500. While the LSU Veterinary Teaching Hospital typically remains open during hurricanes, please call first to be sure the hospital is accessible and veterinary teams are able to accept patients following a disaster. 

On June 3, a 23-year-old pony mare in Sonoma County, California, tested positive for equine herpesvirus myeloencephalopathy (EHM) secondary to equine herpesvirus-1 (EHV-1). The mare initially became ataxia on June 1. She was euthanized, and 36 potentially exposed horses on the home premises are under quarantine. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and EHM.

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.

One foal at a stable in Estrie, Quebec, recently tested positive for rotavirus after presenting with diarrhea. It is unknown if other horses are exposed.

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

One horse at a private facility in Whatcom County, Washington, recently tested positive for pigeon fever. The horse had been colicky and nonresponsive and was euthanized. Necropsy revealed massive internal adhesions and abscessation.

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Pigeon Fever

Pigeon fever is a bacterial infection that affects cattle and horses. It can cause large abscesses, most commonly on the chest and under the belly. Horses become infected when bacteria enters through broken skin, such as small scrapes or wounds. Peak season for infection is late summer through fall.

Good horse health safety practices are key to limiting the spread of pigeon fever. These practices include:

• Fly control;
• Not sharing water buckets or equipment; and
• Avoiding tying horses in high-traffic areas.

If a horse owner suspects that their animal is affected, they should contact their veterinarian.

Q. I am an avid event rider and enjoyed watching the Defender Kentucky Three-Day Event. What kinds of nutritional support can you give horses competing in this level of competition to help them recover?

A. This is a great question. Any post-competition recovery effort starts with the base diet, which meet the horse’s daily requirements leading up to the competition. No long-term deficiency is going to get fixed in the short period during competition, so a balanced diet appropriate for the horse’s discipline and work level is crucial.

Part of that is ensuring the horse is getting the right kind of fuel to support the type of work that he’s asked to do. Event horses won’t only be utilizing stored carbohydrate on cross-country day but hopefully their reserves of fat stores, as well. Cross-country efforts will deplete glycogen stores (stored carbohydrates) in the horse’s muscles. The horse will need glycogen again for the show jumping phase, so restoring those stores is an important component of recovery.

Horses don’t restore muscle glycogen after heavy work particularly quickly, however—it can take up to 72 hours to fully replenish this important fuel source. The tactics human athletes use—such as “carb loading”—don’t work particularly well in horses. Not only has research found carb loading horses relatively ineffective at increasing muscle glycogen, loading with carbs such as starch could lead to colic.

Hydration

One thing that does help improve glycogen replenishment is making sure the horse is adequately hydrated. Muscle glycogen requires water for storage, so a dehydrated horse is less able to generate new muscle glycogen stores.

Hydration measures should begin well before cross-county day. Many horse travel long distances to events, and these long journeys cause surprisingly large amounts of sweat loss. Even when you can’t see the sweat, horses can lose very high levels of electrolytes during transportation. This puts them at a disadvantage before the competition even starts. Feeding salt every day and adding a well-formulated electrolyte while traveling will help horses remain hydrated. Consider arriving a day early if travel is particularly long, so your horse has time to fully rehydrate and recover from the journey before competition starts.

Horses that drink saline solution after exercise have been shown to consume more water in the subsequent hours than those that drink plain water. Consider acclimating your horse to drinking water after work with either salt or electrolytes so this is a normal practice at events.

Muscle Recovery

Hard-working horses might be muscle-sore after cross-country, and supporting recovering muscle might help your horse come out on Day Three with a little more spring in his step. Vitamin E is an extremely important antioxidant for muscle health. Oxidation of glycogen and fats to create energy for muscle contraction causes the formation of free radicals. These oxidizing compounds are unstable and damage cell walls if not removed. Vitamin E helps stabilize them by donating an electron so that a cascade of free radical damage is prevented.

Horses need to get adequate vitamin E every day and, because of individual variation, some horses—even when receiving enough vitamin E to meet the National Research Council guidelines—are vitamin E-deficient. The best way to know your horse is getting enough vitamin E is to ensure his base diet is meeting the stated requirement. Then have your veterinarian test his serum vitamin E levels. This will tell you whether you need to supplement additional vitamin E daily. Providing extra natural vitamin E after particularly heavy work such as cross-country day might aid in recovery.

During recovery from exercise, muscle protein synthesis increases in order to repair muscle tissue damaged during work. If adequate dietary amino acids are available in the 24 to 48 hours post work, a net protein gain might occur. The most important amino acid for this process is leucine, which is a branched chain amino acid (BCAA). For this reason, administering a supplement that provides BCAAs after especially heavy exercise might help shorten recovery.

Take-Home Message

In general, after strenuous exercise, ensure your horse has access to good-quality forage (this is a safe way to replenish carbohydrates and encourages water intake), increase electrolyte intake to replace losses and encourage water consumption, ensure adequate natural vitamin E, and provide BCAAs. Incorporating these into your program will help your horse be at his best for the third day as well as recover from the overall event as quickly as possible.

Healthy, well-maintained hooves can remain strong and functional for decades—supporting horses from their first wobbly steps to their final years.

Hellhole Mare was, actually, an angel of a horse. A cherished favorite among equine hoof scientists who study Brumbies—Australia’s free-roaming feral horses—the tough but gentle bay had given birth to at least 15 foals before becoming so thin and weak that researchers opted to humanely euthanize her.

When the scientists, with heavy hearts, examined this beloved matriarch, they discovered “skin and bones” and toothless jaws, says Chris Pollitt, BVSc, PhD, head of the Australian Equine Laminitis Research Unit at the University of Queensland.

One part of her body, however, showed no signs of age whatsoever—the very foundation she’d been standing on for nearly three decades. Her feet. “Nicely beveled along the edges, strong heels, no laminitis, perfect,” says Pollitt. “You’d think they’d been trimmed by a professional.”

For Pollitt and his colleagues Hellhole Mare epitomizes the equine hoof. “She was nearly 30 years old, but she had the feet of a 5-year-old,” he says, having lived in what Pollitt considers an ideal environment for natural hoof care in an unridden and freeroaming horse. “This tells us that if a horse’s foot is properly cared for, it will be perfect when the horse reaches the end of its life.”

Horse Hooves In Utero

Hooves form remarkably fast, becoming easily recognizable within 65 days of gestation, says Simon Curtis, PhD, FWCF, Hon-AssocRCVS, a farrier in Newmarket, U.K. That’s before limbs have bones, he says.

To prevent uterine damage from fetal kicks, an unborn foal develops a gelatinous horn covering. This protective layer, called the eponychium or deciduous hoof, is derived in part from the sole and white line.

The basic hoof structure fully forms before birth, Pollitt says. But because unborn foals’ hooves never bear weight, their suspensory apparatus—where the coffin bone hangs from the front hoof wall via lamellar structures—remains underdeveloped. The lamellae, which help distribute weight and support hoof function, also do not fully develop before birth. In fact, he explains that because of that lack of weight-bearing, the embryonic hoof’s first and second lamellae form a distinct crisscross pattern, positioned almost perpendicular to each other.

The First Five Months

Healthy foals usually make a wobbly stand on their hooves within the first hour of birth, and they shed their eponychium within a few hours. Pollitt says such weightbearing triggers immediate loading of the suspensory apparatus. Within a couple of days, lamellar structure angles already reflect their new loading—taking on the oblique form they maintain for the rest of the foal’s life.

Meanwhile, their tiny hooves start growing their first palmar processes—a sort of “hook at the back of the bone to which the cartilage is attached”—which are completely absent at birth, Pollitt says.

Despite these changes, though, foal hooves evolve in neither shape nor structure after birth. “The original foal hoof is a certain size—say, the size of a cup—and it can’t grow any bigger,” he explains.

Instead, new horn grows rapidly from the coronary band, at a rate of about 15 millimeters per month, to create a new, mature hoof that widens and flattens over approximately five months, says Curtis. In general, that leaves a clearly visible horizontal “birthmark” line on the descending horn.

This creates a sort of “inverse cone” by three or four months of age, with greater width at the coronary band than the bottom, he explains. That’s, in part, because the foal’s hoof wall thickens more than threefold as it grows from the top down.

Meanwhile, other structures inside the foot—bones and lamellar attachments, for example—must grow along with the horse, Pollitt adds. “Lots of things are happening inside the hoof capsule after birth,” he says. “And all of these changes have to occur in synchrony, in a coordinated fashion.”

In general, this runs remarkably smoothly, he says. “It’s marvelous to consider what—and how many—things could go wrong,” he explains. “It’s like a miracle.”

Still, things can go wrong, especially when conditions aren’t favorable to good hoof growth. Selective breeding for big bodies and small hooves, for example, can negatively impact hoof development. Rigid or oversoft terrains can as well, as the researchers have seen in feral horses.

The first few months also represent the sweet spot for club foot development. Typically, hoof horn at the heel grows faster than at the toe, which occurs especially when foals favor walking on their toes, Curtis adds. Club feet, characterized by an upright shape, long, contracted heels, and a pronounced or bulging coronary band, can sometimes go unnoticed for months or years. In his research, however, he has found they usually appear between 20 and 110 days.

In domestic settings these early months represent a critical time for skilled, frequent trimming to prevent club feet, angular deformities, and other distortions, Pollitt says.

The Rest of the First Year

As foals continue to grow, their hooves undergo significant changes as they gradually develop into the familiar adult form.

“Suddenly we see this hoof taking on the shape that we associate with hooves—which is now a truncated, oblique cone, that leans slightly backward,” Curtis explains.

The new, mature hoof structure usually lasts the rest of horses’ lives, Pollitt says.

Minor tweaks do continue. Horn growth, for example, gradually slows to around 9 millimeters per month by the horse’s first birthday, Curtis says.

Loading patterns—which start as weanlings but become more prominent as the horse’s weight increases—also come into further play, he says. Through pressure readings he found horses “don’t stand like table legs” but, rather, favor inner (toward their midline) versus outer hoof-wall loading.

Suspecting that loading was impacting natural hoof growth patterns, Curtis sought to “separate the changes horses are preprogrammed to experience versus those in response to uneven loading.” He realized the horn compresses under the horse’s weight. That means even if the hoof grows at the same rate across the coronary band, it ends up seeming shorter or longer in different parts of the hoof due to getting smashed.

As a result, the outer angles from the sole to the coronary band appear more oblique, or slanted, and give the impression that outer walls grow faster.

“Farriers recognize this, and they say it grows more hoof on the outside,” he says. “But it’s not because of the production of horn cells; it’s because of the compression.”

Dorsal (front wall) angles also change in the first year at a rate of about one degree per month until about 10 months of age, Curtis says. “So, there’s an extraordinary change in angle.”

Hooves During the Rest of Life

Once a hoof has become mature—at around 10 months of age—it changes very little in healthy horses, says Pollitt.

“My feeling is that horse’s hooves, once grown and once properly cared for and in the right environment, will virtually outlive the horse,” he says.

“A lot of people think that they age—and they’ll tell you that they do, and they’ll supply anecdotal evidence to support that,” he adds. “But my experience is that they’re a wonderful piece of evolution that serves the horse well throughout its life.”

Even so, minor natural changes occur, Curtis says. For example, hoof wall thickness increases to about 9.5 millimeters in an adult Thoroughbred, or around 11 millimeters in other breeds. And horn growth slows to about 6 millimeters per month for adults and even to 3 millimeters per month for seniors.

Researchers on an ongoing pilot study, meanwhile, seem to have confirmed what many farriers have long suspected—that with age, hoof angles continue to mildly flatten compared to the ground, Curtis says.

Still, it’s also possible older horses simply have changing hoof angles due to evolving trimming techniques, especially as owners change farriers, Pollitt says.

Despite these minor changes, though, our sources say owners often perceive age-related changes in their horses’ hooves. “It’s such a rarity that farriers find horses with symmetrical hooves,” Curtis says, and that might be in large part due to unnatural loading rather than age itself.

Age-Related Conditions

While hooves can remain strong over time, they are still vulnerable to age-related diseases and other conditions.

Many older horses suffer from low-grade laminitis, Curtis says. It is often due to excess nutrients, which weaken the laminae by altering the endocrine system, usually in combination with obesity. Besides contributing to rotation or sinking of the coffin bone within the hoof, that excess weight causes compression, especially along the sole.

Horses with age-related insulin resistance—especially related to pituitary pars intermedia dysfunction (PPID, equine Cushing’s disease) and/or obesity—can have chronic laminitic changes, Pollitt says.

That could mean they have a healthy back half of the foot but compression and changes in blood supply to the front half, Curtis says. These issues combined with a slight change in hoof angle could make the problem even more pronounced.

“As a horse ages, you might notice some changes in its hoof that are more related to age-related health conditions, such as Cushing’s (PPID), rather than changes in the hoof due to older age,” says Shannon Pratt-Phillips, PhD, a professor of equine nutrition in North Carolina State University’s Department of Animal Science, in Raleigh. “Good nutrition will still be important to support hoof health even with confounding factors such as Cushing’s or insulin dysregulation.”

Beyond endocrine disorders, geriatric horses simply have more years of impact on their feet—meaning greater chances of injury, such as to the coronary band, Curtis says. “Older horses definitely tend to have more problems, but I think it’s more a cumulative effect,” he explains. “There’s not a single problem that’s more a 20-year-old hoof compared to a 5-year-old hoof.”

Other issues might stem from a lifetime of environmental challenges—such as feral New Zealand horses navigating through rough terrain—rather than the aging itself, Pollitt says.

Likewise, aging, retired domestic horses could suffer from poor hoof health simply because they might receive less hoof care, he explains.

“A lot of people neglect their old horses,” he says. “Of course, if the environment is soft underfoot, they’ll develop long cracks, and they might be euthanized because of the condition of their feet. And (owners) say they’re an old horse with an old foot. But I don’t believe that, intrinsically, there’s aging about the hoof.”

Older horses might also experience nutritional and environmental deficits due to their decreasing social rank, says Pratt-Phillips.

“They end up standing in the mud all the time, or not getting their full ration, because the higher-ranking horses take their place,” she explains.

“Of course, the horse is old, and there will be the assumption that it’s getting old and, so, the hoof is falling away,” Pollitt says. “But in my experience many horses reach old age with hooves that are the same as when they were 3 years old.”

Take-Home Message

Hooves are phenomenal structures built to last a horse’s lifetime. Even so, they experience major changes in shape and structure through the first year out of the womb, while they adjust to bearing the weight of the foal. Once mature, healthy and properly maintained horse hooves can remain strong and functional throughout an animal’s life—provided equine veterinarians and horse owners manage all age-related diseases.

This article is from the Older Horse 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.

Understanding the important role electrolytes play in healthy performance horses

Electrolytes are minerals that break up into electrically charged ions in water. They play crucial roles in the functions of all cells and are particularly important for muscle and nerve function and fluid balance within the horse’s body. When horses sweat, they lose a significant amount of electrolytes from their body. These must be replaced for the horse to maintain optimal fluid balance, nerve function, and muscle function.

Manufacturers market a plethora of electrolyte products in a variety of forms to horse owners. Understanding when, how much, and which products to supplement is critical for optimizing equine health and performance.

Another Kind of Sweat Equity

When your horse sweats, you might see a white residue that remains on his hair coat after the sweat evaporates. Those are the residual electrolytes lost through sweat. Therefore, even by simply looking at a working horse it becomes obvious that the more he sweats, the more electrolytes he has lost. The primary electrolytes a horse loses in sweat are sodium, chloride, and potassium. He also loses calcium, magnesium, phosphorus, and sulfur, but in smaller quantities.

Don Kapper, a professional animal scientist based in Beach City, Ohio, with more than 37 years of experience formulating products, researching, and teaching in the industry, says, “Electrolytes are anions and cations (negatively and positively charged ions, respectively), so the positives and negatives must work together. When the horse runs out of cation or anion molecules the muscle will stop functioning properly. Therefore, when electrolytes are supplemented, the anions and cations must be balanced and match what the horse has lost in their sweat.”

Why Do Horses Need Supplemental Electrolytes?

Electrolytes tend to be front of horse owners’ minds in the summer months but, regardless of season, if a horse sweats, he should consume supplemental electrolytes. Sweating is the primary method of thermoregulation for working horses. Therefore, when temperatures increase, electrolyte losses are more substantial. Michael Lindinger, PhD, a former professor at the University of Guelph, in Ontario, Canada, and current president of the Nutraceutical Alliance, also in Ontario, notes, “When horses sweat, they are losing a lot of electrolytes through their skin, nearly three times more than humans. Therefore, if the horse is sweating even for just one hour, they can lose a significant amount and may become dehydrated.”

The electrolyte levels your horse needs are directly proportional to what he loses in sweat. In order to decipher how much you should be supplementing, rely on the National Weather Service’s heat index chart (weather.gov/ffc/hichart). This chart takes into consideration the day’s temperature, humidity, and work intensity level. Due to horse sweat being more concentrated with electrolytes than human sweat, it is imperative we provide electrolytes to dehydrated horses and don’t just give them water.

When a dehydrated horse receives plain water but cannot replenish electrolytes, it can negatively affect his ability to recover. “A key role of electrolytes is that they retain fluid in the body, both within cells (intracellularly) and outside of cells (extracellularly). Therefore, the only way to rehydrate a dehydrated horse is to restore hydration with a solution of water and electrolytes,” says Lindinger.

The Benefits of Supplementing Electrolytes

Lindinger, in a study published in the Journal of Experimental Physiology, demonstrated that providing a properly formulated oral performance electrolyte administered in solution at the recommended rate can delay the onset of fatigue by over 22%, reduce muscle cramping, and improve the horse’s ability to recover and perform the following day.

Kapper notes, “During this research, the electrolyte was detected in the bloodstream within 10 minutes of administration, and within 10 minutes of starting to exercise was present in the sweat.” To do this, the optimal osmolarity (concentration) of the performance electrolyte solution must be attained. The amount of electrolyte powder Lindinger and his team used was 4 ounces/gallon of water.

Indeed, to capture the benefits of electrolyte supplementation described, it is not always enough to simply provide salt and water to your horse.

Our sources don’t consider many commercially available electrolyte products properly formulated as performance products. A performance electrolyte replenishes what the horse has lost in his sweat. So if the product does not match the losses, it might not be effective for hydrating the horse, delaying fatigue, or improving his ability to recover from work.

Performance Electrolytes

The chemical makeup of equine sweat expressed as an equation is Na + K + Ca + Mg = Cl + P + S. Again, “performance electrolytes are those that emulate what has been lost in sweat,” says Kapper. “The addition of dextrose also improves the rate of absorption in the small intestine. When you are choosing a performance electrolyte for your horse, the sodium and potassium should be close to equaling the amount of chloride in the product.” You can find this information in the guaranteed analysis of the product.

Understanding ideal formulation of performance electrolytes is critical to choosing the right product for your hard-working horse. For instance, Himalayan salt and sea salt are very popular among horse owners. “However, they are very different from the electrolyte composition of sweat and, therefore, poor choices when aiming to rehydrate a horse after working,” says Lindinger.

“Supplements containing greater than 70% salt (NaCl₄) are not performance electrolytes. They are simply expensive salt,” adds Kapper.

Therefore, when shopping for an optimal performance electrolyte product for your horse, read the guaranteed analysis and compare it to the equation of electrolytes in equine sweat. Nutritionists typically recommend using salt to meet your horse’s daily sodium and chloride requirement and then adding a performance electrolyte when he starts sweating.

Consequences of Dehydration and Electrolyte Imbalance

Dehydration has a variety of negative consequences ranging from fatigue and weakness to serious health issues such as colic and tying-up. Kapper says, “Most horse owners are familiar with the skin-tent test and looking at the color of the gums when assessing for dehydration. However 14 other parameters exist that horse owners can check. The Horse Health Check (tool), developed by Art King, DVM, and Gayle Ecker at the University of Guelph, details 16 checkpoints to evaluate dehydration.”

As mentioned earlier, when a horse has lost electrolytes in his sweat and becomes dehydrated, the body will stop working properly. “Nerves and muscles will stop functioning,” says Lindinger.

Kapper adds, “The positive and negative (electrolytes) must work together so, when there is an imbalance, the horse owner will notice muscle soreness starting, more stumbling, and a shortened stride.” When considering elite performance horses that compete multiple days in a row, delaying fatigue and muscle soreness can make a significant difference in their abilities to successfully perform.

Administering Electrolytes to Horses

When selecting from the myriad equine electrolyte products and administration methods available, horse owners must understand how the horse’s body absorbs electrolytes and how they contribute to rehydration.

“All electrolytes are hydroscopic and will dehydrate your horse if they do not drink enough water after administering,” explains Kapper. For this reason, adding the electrolytes into an appropriate volume of water for dehydrated horses is extremely critical.

Additionally, he does not recommend paste electrolytes for this reason. “All paste electrolytes will lie in the digestive tract of the horse until they draw enough water from the body to break them down,” he adds.

When mixing the solution, follow the manufacturer’s instructions. “Use concentrations that are more dilute if palatability is an issue,” says Lindinger.

One of the biggest challenges owners face when supplementing electrolytes in their horses is determining how much they should offer, and if top-dressing over feed is adequate or if they need it in solution. “Feeding electrolytes as a top dressing is common, however, this should not be done for a dehydrated horse,” says Lindinger.

Providing the electrolyte in solution is the gold standard, but for horses traveling, idle, or at lower levels, top dressing the performance electrolyte on feed at the recommended amount per day is often adequate. For horses at the upper levels and exercising intensely, the electrolyte solution should be provided during and after transport to events to ensure optimal hydration prior to training and competition sessions. In addition, electrolytes are best provided within 45 minutes after training or competing.

“Relying on the average heart rate of the training session can assist horse owners in determining how much electrolyte to give,” notes Kapper. “For example, a horse that is sweating for 15 minutes during a work session will not require the same electrolyte supplementation as an endurance horse doing 100 miles per day.”

Kapper’s charts summarize electrolyte supplementation recommendations in various situations.

Supplementation Recommendations for ‘MILD’ Heat Stress Index (Below go)

Supplementation Recommendations for ‘MODERATE’ Heat Stress Index (90-105)

Supplementation Recommendations for ‘SEVERE’ Heat Stress Index (Over 105)

Tips for Supplementing Finicky Horses

When introducing a performance electrolyte to your horse’s diet, start it at home—not at an event or during travel. “Buy a small amount of the performance electrolyte and try it, especially with finicky horses,” says Kapper. If you sometimes add it as a top dressing and other times mix the product into water, Kapper recommends using the same product both places to ensure taste consistency.

“When introducing a performance electrolyte mixed with the horse’s water, start with a dilute solution and, over the course of multiple days, slowly increase the concentration to full strength,” says Lindinger. If your horse does not like one product, do not hesitate to try a different one.

Including dextrose in performance electrolytes should improve palatability. Nutritionists know that when sugar content exceeds what the body needs, muscles will weaken but, as noted earlier, adding dextrose to performance electrolytes improves absorption. Some practitioners don’t recommend adding electrolytes to feed or water because of the risk of decreasing feed consumption and causing dehydration; instead, they recommend a free-choice electrolyte. What you offer depends on the horse.

Take-Home Message

When horses sweat, they lose a significant amount of electrolytes that must be replaced to help them maintain adequate fluid balance as well as muscle and nerve function. Dehydration can be detrimental to equine health and performance. Therefore, adopt effective electrolyte supplementation strategies to promote hydration. Remember to critically review the  guaranteed analysis prior to purchasing a performance electrolyte and introduce it to your horse to consume at home prior to traveling or competing in warmer weather.

Lyme isn’t the only tick-borne illness horse owners need to consider

Lyme is the tick-borne disease most people think of first, but it isn’t the only one. Anaplasmosis is another disease of clinical significance in horses, and other diseases might be on the rise (Have you heard of ehrlichiosis in horses?). In this story we’ll look at what ticks are troublesome to horses, when and where they can be found, then discuss the clinical signs, diagnosis, and treatment of anaplasmosis, the “other” tick-borne disease that always seems to take a back seat to Lyme.

Which Ticks are Found on Horses?

In the U.S., many hard ticks infest horses, including the American dog tick (Dermacentor variabilis), the winter tick (Dermacentor albipictus), the lone star tick (Amblyomma Americanum), the Gulf Coast tick (A. maculatum), and the black-legged tick (Ixodes scapularis).

“Of particular interest to horse owners and veterinarians is the ability of these ticks to transmit disease agents,” says Kathryn Duncan, DVM, PhD, Dipl. ACVM, adjunct assistant professor at Oklahoma State University, in Stillwater, who has studied the subject with colleague Kellee Sundstrom, MS, senior research specialist. “Occasionally, a foreign animal disease, such as equine piroplasmosis, is diagnosed in the U.S. Ticks can be implicated as the cause of transmission, but the tick-borne disease agents most often transmitted to horses are through a bite from Ixodes species.” 

Where Ticks are Found

Geographically Traditionally, I. scapularis are found in the eastern parts of the United States, whereas I. pacificus are found along the West Coast, including California, Washington, and Oregon, with a few reports coming from Nevada and Utah. With continued biogeographical changes, however, the “natural” ranges of ticks are evolving, experts say, and many ticks are found well outside what has been considered their traditional geographical areas.

Sonenshine et al. (2018) reported that the main reason for expansion of ticks is climate change, notably the rapidly rising global temperatures. That said, host availability and specificity, habitat suitability, relative humidity tolerance, the extent and duration of freezing temperatures, and human impact (habitat modification) all contribute. As an example of expanding tick ranges, Sonenshine et al. noted that I. scapularis densities have also intensified in many areas, and they appear to be advancing into parts of southern Canada at a rate of about 46 km (28.5 miles)/year.

Anatomically (on the Horse) In a study on horses in northeastern Oklahoma, Sundstrom et al. (2021) looked at the types of ticks infesting horses and the preferred site of attachment. Client-owned horses residing on eight farms were examined twice monthly for one year. Researchers collected ticks from those horses and recorded the anatomic location of attachment. They included 88 horses in the study, and 84.1% of horses were infested with ticks at least once during the study period.

The median number of ticks per horse was three. Researchers identified five different tick species, the most common being A. Americanum—the lone star tick (78.2%)—followed by I. scapularis, which was much less prevalent (18.2%). They found the lone star tick most often attached in the inguinal region (groin), and they found I. scapularis primarily on the chest and armpits (axilla) of the horses.

What Times of Year In that same study Sundstrom et al. also noted ticks were discovered on horses year-round in northeastern Oklahoma with the largest number seen in May. I. scapularis predominated October through February and was still common in March.

“The belief that ticks are only out in the summer is a myth that many tick researchers and veterinarians have been trying to bust for a while now,” explains Duncan. “Tick numbers may decline in the winter, but the extent to which this happens is dependent on the geographic region.”

In fact, she says that Ixodes spp and D. albipictus prefer cooler months.

“Ticks will ‘overwinter’ in leaf litter, under snow cover, and in reservoir host habitats but reemerge when there are ample hosts available and slightly warmer days,” Duncan explains. “In order to reemerge in the spring, some stages are required to survive the winters. With milder winters and premature emergence of warm weather, we can expect ticks to be noted earlier than we’ve seen in the past. This is likely a trend that will remain based on continued tick habitat changes.”

A Look at Anaplasmosis (and Some Comparisons to Lyme)

This disease is caused by an infection with Anaplasma phagocytophilum, which is a type of bacterium in the rickettsial group. These bacteria must live inside the cells of the infected animal. With anaplasmosis, the bacteria live inside white blood cells, which are also called granulocytes. This is why veterinarians also refer to anaplasmosis as equine granulocytic anaplasmosis (EGA). In contrast, the bacterial spirochete Borrelia burgdorferi causes Lyme disease.

Similar to Lyme disease, A. phagocytophilum is transmitted to horses via the bite of an infected black-legged tick—I. scapularis, I. pacificus, and other Ixodes spp. After the bite, the tick injects the bacterium into the horse’s skin. Migrating granulocytes respond to the local inflammation and engulf the bacteria, attempting to kill them.

“But A. phagocytophilum is now exactly where it wants to be, inside the cell, where it is able to avoid natural immune defenses,” says Duncan. “Disease symptoms are caused by natural immune chemicals like interferon trying to fight off the infected cells. It takes about one week before the horse begins showing signs of disease.”

Clinical Signs of Anaplasmosis

Classic clinical signs of anaplasmosis can be as mild as the horse having a fever, depression, subtle limb edema (fluid swelling), and ataxia (incoordination).

“Many horses with anaplasmosis probably don’t show any clinical signs at all,” says Janet Foley, DVM, PhD, professor in the Department of Medicine and Epidemiology at the University of California, Davis (UC Davis), School of Veterinary Medicine.

More severe signs, which typically develop in older, geriatric horses, include loss of appetite, reluctance to move, icterus (jaundice), and petechiae, which are small pinpoint bruises on the skin.

When present, the fever is quite high, usually 103-104 F, but can reach 107-108 F and lasts for about five days.

That said, tick-borne diseases are true masters of disguise, and researchers have described various other clinical presentations. John Madigan, DVM, MS, Dipl. ACVIM, a professor in the Department of Medicine and Epidemiology at the UC Davis School of Veterinary Medicine, recently published an article describing one horse with dysphagia (difficulty swallowing) and another with respiratory distress attributable to anaplasmosis (2021).

Veterinary Diagnosis

Horses with potential exposure to ticks—essentially, those in every state in the U.S.—presenting with the above-described clinical signs, particularly a high fever, should be tested for anaplasmosis.

“A horse presenting with a high-ish fever that resides in a place that overlaps
geographically with I. pacificus would definitely make you want to test for anaplasmosis,” says Foley.

Testing includes the following steps:

• A complete blood cell count. Typical findings include either a decrease in white blood cell counts or a decrease in all three cell lines: white blood cells, red blood cells, and platelets. This latter presentation is called pancytopenia.
• Microscopic analysis of the blood cells. The white blood cells might show “cytoplasmic inclusion bodies,” which are the rickettsial organisms living inside the granulocytes.
• A polymerase chain reaction (PCR) test, a molecular method for detecting DNA of the bacterium in a horse’s blood sample.
• The IDEXX SNAP 4Dx that detects antibodies to anaplasmosis. It provides a “positive” or “negative” indication for antibodies, but it does not confirm an active infection.
• An immunofluorescence antibody test (IFAT) that identifies antibodies against A. phagocytophilum. Veterinarians must interpret this result with caution, however, because many horses living in areas where hard ticks are endemic might have those antibodies.
• Acute and convalescent titers. This is an IFAT performed when the horse is first sick to measure the antibody levels, then again two to four weeks later. The antibody levels increase about fourfold in horses that have been actively infected.

Anaplasmosis must be differentiated from other diseases. Because horses can exhibit ataxia, the top differentials include viral encephalitides such as equine herpesvirus myeloencephalopathy (EHM), West Nile virus, and the Eastern and Western encephalitis viruses. Other conditions to consider are liver disease (because of the jaundice); purpura hemorrhagica, which is a secondary complication to strangles (Streptococcus equi bacterial) infection; viral arteritis; and even the reportable and highly fatal disease equine infectious anemia (EIA). 

Treating Anaplasmosis

Like Lyme disease, anaplasmosis is easily treatable. Veterinarians’ antibiotic of choice is oxytetracycline.

“There are different treatment protocols out there, but a standard full course of antibiotics is appropriate, 10 days,” says Foley.

For more severely affected horses, practitioners can administer corticosteroids in addition to intravenous fluids and nonsteroidal anti-inflammatories.

Unlike many other diseases that fail to spare the feet, few horses with anaplasmosis ever develop laminitis.

How Commonly Does Anaplasmosis Strike?

“In Northern California, anaplasmosis is actually pretty common,” says Foley.

Duncan agrees, adding, “These infections are probably more common than we realize. But considering most horses are never tested for tick-borne diseases, we can’t know for sure.”

Nonetheless, tick-borne diseases are frequently considered as causes for disease (i.e., fever, lethargy, lameness, ataxia) in horses where ticks are endemic. But a Pennsylvania survey shows that infection with A. phagocytophilum and B. burgdorferi is not all that common even though ticks are commonly found in the state.

In that survey Thompson et al. analyzed blood samples collected from 271 horses whose veterinarians suspected tick-borne disease. The researchers used PCR to detect DNA from both bacteria and used the IDEXX SNAP 4Dx and an IFAT to detect antibodies.  

Key findings were:

• Researchers identified DNA for A. phagocytophilium in 7% of the horses. They did not find B. burgdorferi DNA in any horse;
• They detected antibodies to A. phagocytophilium and B. burgdorferi in 28.4% and 67.9% of horses, respectively;
• With IFAT they discovered antibody titers of 1:50 or more in 41.3% and 60.5% of horses for A. phagocytophilium and B. burgdorferi, respectively.

The high prevalence of antibodies to both bacteria in this survey shows that horses in Pennsylvania, where ticks are common, could have prolonged, repeated exposure to these pathogens (TheHorse.com/1118403).

“Again, though, simply identifying antibodies does not confirm that either of these bacteria are causing the disease. The presence of antibodies simply proves exposure to the bacteria,” says Foley.

The lack of B. burgdorferi DNA found in that study wasn’t surprising because the bacteria do not persist in the bloodstream for very long.

“For Lyme disease the bacteria can be sequestered in the joint, as well as any connective tissue, including kidney capsule, etc. For anaplasmosis, though, we do expect circulating blood to be PCR-positive during active infection,” says Foley. 

Identifying A. phagocytophilium DNA together with the lack of circulating antibodies in the bloodstream (the body hasn’t had time to produce them yet) and the presence of high fever or other clinical signs consistent with disease supports a diagnosis of anaplasmosis.

Emerging Tick-Borne Diseases

While Lyme, anaplasmosis, and piroplasmosis are the only three tick-borne diseases discussed in the U.S. for equids, surveys from other regions suggest Rickettsia spp and Ehrlichia spp might be clinically relevant in horses.

Therefore, Duncan et al. (2022) wanted to better understand the transmission risk of these tick-borne rickettsial disease agents.  In their study they tested ticks from horses residing in Oklahoma using PCR.

Additionally, they analyzed blood samples from horses both infested and not infested with ticks for antibodies to these bacteria.

They reported that illnesses caused by Rickettsia spp and Ehrlichia spp could be emerging tick-borne diseases in horses.

“We found that one-quarter of the ticks recovered from tick-infested horses contained DNA of Rickettsia spp, and R. amblyommatis was the most common species identified. This is part of the spotted fever group of bacteria, is transmitted by the lone star tick, and is currently considered nonpathogenic,” relays Duncan. “Ehrlichia spp were found far less commonly in ticks recovered from horses.”

In contrast, researchers did not find circulating antibodies for R. rickettsii in any of the study horses, but almost 30% of horses had antibodies for Ehrlichia spp.

“These results suggest there is a need to further explore the role of Rickettsia spp and Ehrlichia spp in equine health,” states Duncan.

The fact other diseases might also be transmitted by ticks isn’t surprising, considering ticks are known to transmit several different disease agents to humans in addition to Borrelia and Anaplasma. Examples include the agents of Rocky Mountain spotted fever, ehrlichiosis, tularemia, babesiosis, Colorado tick fever, and Powassan virus disease, among others.  

Take-Home Message

Some of the main takeaways from the current research are:

1. Many tick types can infest horses, but few are currently known to actually transmit disease to horses;
2. Tick ranges are expanding, so ticks are found in geographical ranges and at times of year they haven’t previously been found;
3. Anaplasmosis can occur commonly in certain geographic areas and should be considered as important a tick-borne disease as Lyme disease.

“If residing in a region with a heavy tick burden, be aware of practices to prevent tick-borne diseases including using regular tick control, screening annually with an antibody test, and performing thorough tick checks with proper removal,” advises Duncan.

This article first appeared in The Horse‘s Preventive Care Special Issue, which was distributed in June 2024. 

How a 21-year-old Hanoverian gelding stayed competitive at the Florida winter circuit

Many horse owners, riders, and trainers expect their horses’ athletic potential to diminish as they enter their later years; however, some horses remain healthy and happy in their work well past what many would consider their peak years. As horses age, they might experience more joint pain associated with osteoarthritis, digestive problems or a decline in gut health, or decreased performance. Fortunately, with advancements in equine medicine, veterinarians can work with horses’ trainers and care teams to help ensure long-term soundness.

The Crucial Equine Vet-Client-Patient Relationship

Successfully maintaining a horse in the top levels of competition throughout his later years requires a close relationship between the rider or trainer and veterinarian. “The rider is the person who spends the time on the horse’s back and feels differences in a gait transition or that a canter lead feels (different) one way versus the other,” says Kate Britton, DVM, of Atlantic Equine Services in Dover, New Hampshire, and Wellington, Florida.

These small details are crucial to the overall picture, especially when combined with information from the horse’s competition performance and a clinical exam. Meanwhile, don’t forget to keep the owner in the loop. “Keeping an open relationship with the owner is paramount to the health and success of the horse as they are the ones standing behind the horse with all parties involved on both good and bad days,” she adds. 

Maintaining Mindful at the Top Levels of Sport

Jennifer Hannan, rider and trainer, of Ocean Echo Farm in Wakefield, Rhode Island, and Wellington, has been training Mindful, a 21-year-old Hanoverian gelding owned by Selma Garber and Kensel LLC, since 2017. (Mindful started his US Equestrian-recognized showing career in 2013 with a different owner and riders.)

In their years together they have shown at the top venues around the country, such as Palm Beach International (now Wellington International), which Hannan says was the scene for their first international derby win as a pair. “He has since gone on to win seven international derbies at (Palm Beach/Wellington International). He has earned championships at every major horse show on the East Coast.”

Over the years Hannan and her veterinarian, Britton, have worked closely with one another to maintain Mindful’s physical and mental well-being at the highest levels of the sport.

Managing Mindful’s Joint Health

Britton regularly evaluates Mindful—typically monthly, she says, but twice monthly for performance evaluations during periods of intense competition. “Regarding maintenance care, we try to stay ahead of any issues, so (I see him) around four times per year for this.”

To manage any potential joint pain that could affect his performance, Britton treats him with intra-articular (IA) autologous protein solution and 2.5% polyacrylamide hydrogel (not at the same time) based on the results of her regular physical exams and soundness evaluations. “We try to stay ahead of any issues that may arise with his continued career, and we wanted to use the most beneficial treatments for his joints,” she says.

Equine Complementary Therapies and Nutrition

In addition to regular soundness examinations, Mindful also receives consistent veterinary chiropractic adjustments, acupuncture, and massage, which Britton says complement his medical treatments and play an important role in his longevity.

“He goes on a Theraplate daily and turns out as much as possible,” adds Hannan.

“His diet plays a role in his health as far as keeping him fit,” she continues. “We feed an all-natural diet, which is low in sugar, and I really feel like that has helped him in his career with me.” This consists of a forage-based diet (including alfalfa pellets and beet pulp) with non-GMO supplements to fill any nutritional gaps.

Utilizing Equine Fitness for Long-Term Soundness

Hannan works to keep Mindful physically fit year-round to help him maintain a healthy muscular condition and always stay comfortable in his work. “His overall fitness is our main goal,” she says. “We try to keep him fit and happy.”

Mindful stays in a consistent program with a balance of jumping and discipline-specific training days, along with relaxed trail riding and hacking days. “I think it’s important to keep him fit on many different types of surfaces,” says Hannan. “He works in the fields with hills as well as in the ring and even some harder surfaces.” However, Mindful only jumps once a week.

“That may include cavalletti exercises or just a few jumps, so he keeps his fitness,” Hannan adds, noting she rarely schools Mindful over show-height fences, but she might do so once before a show.

She adds that Mindful’s owner allows her to create a detailed training and competition plan for him, without ever pushing him past his physical or mental limits and while keeping his competition schedule light. “We have really been able to tailor his show schedule, physical fitness, and overall soundness (to his individual needs),” says Hannan. “I truly believe all of this has made a huge impact on his unbelievable career.”

Take-Home Message

Caring for horses that continue competing into their senior years demands a close relationship between the riders or trainers and veterinarians as well as careful daily monitoring of any minor changes in the horses’ behavior.

“Always listen to your horse and trust your feeling of them and what they are telling you,” says Britton. “Jenny has an exceptional ability to know minor changes in how her horses are feeling, which I feel helps keep them ahead of major issues.”

Trainers and veterinarians must maintain open communication regarding a horse’s health and performance to keep him sound and happy long-term.

This article is from the Older Horse 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.

On May 29, a 2-year-old Thoroughbred colt in Barn 85 at the Saratoga Race Course in Saratoga County, New York, tested positive for strangles. The horse was shipped to Rood & Riddle Equine Hospital on May 28 for evaluation and treatment of a respiratory infection. He began treatment immediately and was transported from the hospital to a private layup facility. 

Barn 85 is now under quarantine. A 24-hour security watch has been established, and all horses in the barn will receive regular temperature checks. The horses under quarantine are not permitted to enter races or train among the general horse population. Asymptomatic horses in Barn 85 will have isolated training hours at the Oklahoma Training Track following the close of training for the general horse population at 10 a.m. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

On May 28, one horse in Clearwater County, Alberta, was confirmed positive for equine infectious anemia (EIA). The horse was tested after developing clinical signs of disease. Initial reports indicate that there are several other horses on the property. The infected horse and all exposed horses are under quarantine. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About EIA

Equine infectious anemia is a viral disease that attacks horses’ immune systems. The virus is transmitted through the exchange of body fluids from an infected to an uninfected animal, often by blood-feeding insects such as horseflies. It can also be transmitted through the use of blood-contaminated instruments or needles.

A Coggins test screens horses’ blood for antibodies that are indicative of the presence of the EIA virus. Most U.S. states require horses to have proof of a negative Coggins test to travel across state lines.

Once an animal is infected with EIA, it is infected for life and can be a reservoir for the spread of disease. Not all horses show signs of disease, but those that do can exhibit:

• Progressive body condition loss;
• Muscle weakness;
• Poor stamina;
• Fever;
• Depression; and
• Anemia.

EIA has no vaccine and no cure. A horse diagnosed with the disease dies, is euthanized, or must be placed under extremely strict quarantine conditions (at least 200 yards away from unaffected equids) for the rest of his life.

What You Can Expect

• A New Brand Identity: Sweet PDZ will introduce a refreshed visual identity, making the product line even more recognizable and appealing to customers.

• No Change in Product Performance: The same effective, trusted formula that eliminates ammonia, reduces odors, and improves air quality will continue to deliver the quality you expect.

• New Packaging Debuting Soon: Retailers will begin to receive (and consumers begin to see) the updated Sweet PDZ packaging in May, with a full rollout continuing across all Sweet PDZ packaging throughout the remainder of the year.

We believe this updated branding will allow Sweet PDZ to stand out in the marketplace and provide customers with an even more compelling reason to choose this industry-leading ammonia and odor control solution. After more than forty years of providing superior odor control and making barns/stalls safer and healthier, Sweet PDZ remains committed and passionate in providing horse enthusiasts with the best in animal wellness. For any questions or further details on the new look, please reach out to Sweet PDZ at www.sweetpdz.com or 800-367-1534.

In performance horses, every aspect of care—from nutrition and farriery to conditioning and recovery—works together to influence the animal’s long-term soundness and success. Veterinarians or equine nutritionists might recommend supplements as part of multimodal approach to support horses’ overall wellness or help manage chronic conditions. While they’re not intended to replace foundational veterinary care or good nutrition, supplements can complement a comprehensive management plan when thoughtfully selected and used in conjunction with targeted therapies and training programs.

“Supplements should only be used to augment a preexisting care plan,” says Nimet Browne, DVM, MPH, Dipl. ACVIM, of Hagyard Equine Medical Institute, in Lexington, Kentucky. “We need to understand that they are not going to solve all our problems, but they can bring out the best in our athletic partners.”

What Is a Multimodal Approach to Performance Horse Health?

A multimodal management strategy involves using multiple treatments or techniques, each targeting a different aspect of a problem (i.e., pain or inflammation). This could mean pairing a nonsteroidal anti-inflammatory drug (NSAID) with physical therapy or combining regenerative therapies with appropriate nutrition and supportive shoeing.

“By combining different modalities and agents, we hope to achieve a greater level of pain relief,” Browne says. “For example, we might use extracorporeal shock wave therapy in addition to NSAIDs to alleviate back pain.”

Because the FDA classifies only products that treat, cure, or prevent disease as drugs—requiring them to pass rigorous approval processes—most owners turn to supplements to complement the diet or fill nutritional gaps. Supplements have comparatively limited regulatory oversight, meaning owners, veterinarians, and nutritionists should thoroughly research a supplement before feeding it to a horse.

Supplements should never replace foundational management, such as proper conditioning and veterinary diagnostics. “If you’re relying on a supplement to resolve (for example) lameness, it’s very important that you first have a diagnosis so that you know what you are dealing with to know if that product might help,” says Emma Adam, DVM, PhD, Dipl. ACVIM, ACVS, assistant professor at the University of Kentucky’s Gluck Equine Research Center, in Lexington. “Supplements can complement a good program, but they are not a substitute for suboptimal training, nutrition, or management practices.”

How to Evaluate a Supplement for Horses

When choosing a supplement for a performance horse, veterinarians and owners should consider its quality, bioavailability, and clinical backing as the top priorities. “Start by consulting your veterinarian,” Browne says. “They can help identify ingredients and dosages that would help the particular problem you are trying to address.”

For example, she adds, “There are many formulations of vitamin E on the market, but many of them have poor absorption. Working with your veterinarian, you can choose the most appropriate formulation.”

Adam agrees and emphasizes the importance of evidence-based decision-making. “We can’t assume all supplements are the same,” Adam says. “I look for peer-reviewed studies or data that support a supplement’s claims. Products backed by research and developed by reputable companies demonstrate that company’s commitment to their product and to their customer.”

Bioavailability—the rate and extent to which the body can absorb and use an ingredient—can be a critical factor in a supplement’s effectiveness, says Adam. High-quality and verified ingredients, correct dosing, and a horse’s individual metabolism all affect outcomes. “If the supplement isn’t being absorbed, it doesn’t matter how promising it sounds,” she says.

Timing Performance Horse Supplement Administration

Timing of administration can influence a supplement’s efficacy. For example, owners should feed most supplements consistently to maintain steady therapeutic levels. Owners might need to give other supplements, such as those used for recovery or acute stress, around competition. “There are ingredients that help maintain athletic ability and support recovery after a tough workout,” Browne says. “These tend to have a short duration of action and therefore need to be administered closer to competition time.”

Common Equine Supplement Mistakes to Avoid

Horse owners often make the mistake of over supplementing—adding multiple products without a clear plan or awareness of potential ingredient overlaps, says Browne. “Although often not dangerous, doubling up on ingredients can lead to increased expenses and complicate feeding routines,” she says. “It can also make horses reluctant to eat or resistant to oral medications.”

However, in some cases, over supplementing might be risky because little research available to demonstrate how multiple supplements fed together can affect horses, says Adam. “Owners want to do the best for their horses and may be tempted to add product after product, but without guidance and data that strategy is inefficient at best and risky at worst.”

Choosing Equine Supplements as a Team Effort

Ultimately, effective supplement use requires collaboration between veterinarians, farriers, trainers, and owners. This includes being aware of the legal and ethical considerations around supplement use, especially in competition settings.

“It is extremely important that both veterinarians and professionals have a solid understanding of the rules and regulations set forth by the governing body of their sport,” Browne says. “These rules are in place to ensure the health and safety of the equine and human athlete.”

Adam encourages open communication between all involved in a horse’s care. “When everyone’s on the same page, the horse benefits,” she says. “Transparency helps prevent negative interactions and ensures the overall plan is coherent.”

Take-Home Message

When addressing a specific problem in a performance horse, supplements can be one part of the solution and work best when integrated into a larger strategy. Veterinarians, owners, farriers, and nutritionists should work together to create a multimodal management plan for performance horses built on transparency and including high-quality nutrition, routine veterinary care, medical management, and complementary therapies.

“Supplements can be one piece of a comprehensive care plan,” says Adam. “It’s about doing what’s right for each horse, backed by science, experience, and teamwork. Where possible use evidence-based practices rather than anecdotal experience. Always tailor choices to the individual horse’s needs and medical history.”

A 2-week-old foal in Région de Gatineau, Quebec, recently tested positive for rotavirus after developing diarrhea and hepatitis. The foal is recovering, and one additional case is suspected. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

The State Department of Agriculture recently confirmed that one horse in Hall County, Georgia, is positive for pigeon fever. The horse is under voluntary quarantine. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Pigeon Fever

Pigeon fever is a bacterial infection that affects cattle and horses. It can cause large abscesses, most commonly on the chest and under the belly. Horses become infected when bacteria enters through broken skin, such as small scrapes or wounds. Peak season for infection is late summer through fall.

Good horse health safety practices are key to limiting the spread of pigeon fever. These practices include:

• Fly control;
• Not sharing water buckets or equipment; and
• Avoiding tying horses in high-traffic areas.

If a horse owner suspects that their animal is affected, they should contact their veterinarian.

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

On May 22, a 6-year-old Mustang gelding in Eaton County, Michigan, tested positive for strangles. The horse developed clinical signs on May 12, including nasal discharge and swollen submandibular lymph nodes. He is now under quarantine. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

On May 24, a 26-year-old Arabian gelding at a boarding facility in Niagara County, New York, tested positive for strangles. The horse developed clinical signs on May 21, including fever and inappetence. Two additional cases are suspected, and 15 horses are exposed. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

Three horses at a boarding facility in Marion County, Florida, recently tested positive for strangles. The affected horses are under quarantine, and 50 additional horses are exposed. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

On May 22, a 4-year-old Thoroughbred gelding at a boarding facility in Montgomery County, Pennsylvania, tested positive for strangles. The horse developed clinical signs on May 19, including fever and nasal discharge. He is under quarantine, and 39 horses are exposed. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

On May 22, a 20-year-old Quarter Horse mare in Cumberland County, Pennsylvania, tested positive for Potomac horse fever. The horse, who is vaccinated, developed clinical signs on May 18, including fever and colic signs which progressed to liquid diarrhea. She was referred to a hospital in Virginia, where she is responding to medical management.

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Potomac Horse Fever

Potomac horse fever is caused by Neorickettsia risticii, an organism found in parasites, called flukes (flatworms), that infects aquatic snails and insects. Horses can be infected by ingesting insects carrying Potomac horse fever or by drinking water containing N. risticii. Additionally, horses can get Potomac horse fever by inadvertently consuming infected insects or parasites in feed, water, or on pasture.

The incubation period for Potomac horse fever is between one and three weeks, and the mortality rate is up to 30%. While vaccines against Potomac horse fever are not 100% effective, vaccinated horses tend to have fewer and less severe clinical signs.

Most Potomac horse fever cases are reported in July through September, and outbreaks tend to be seasonal.

Horse owners and caretakers, especially those who keep their horses near creeks and rivers, should watch for signs including:

• Diarrhea
• Colic
• Loss of appetite
• Lethargy
• Toxic shock
• Dehydration
• Abortion in pregnant mares
• Laminitis
• Mild to severe fever.

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.

Q. How long does it take for pasture grass sugar levels to drop after the sun goes down?

—Debra, Texas

A. The level of sugar in pasture grass varies due to several factors, including the weather, how stressed the grass is, its maturity, the time of year, and the time of day. As sun shines on pasture grass, the plants photosynthesize. This creates sugar stores the plan uses overnight to keep growing. Therefore, grasses tend to have higher sugar contents later in the day compared to earlier in the day.

Time Pasture Access Carefully

Generally, veterinarians and nutritionists recommend horses sensitive to sugar in pasture grass (such as those with insulin resistance, equine metabolic syndrome, or a history of laminitis) graze very early in the morning. It takes several hours after the sun sets for sugar levels to drop, so ideally try to avoid grazing before 3 a.m. And, because sugar levels start to build up again with sun exposure, it’s best to remove sensitive horses from pasture by about 10 a.m. If there’s significant cloud cover, you might be able to leave horses out a little longer, because photosynthesis (which relies on the sun) will be slower and therefore the amount of sugar will be lower.

One exception would be if the temperature drops below about 40°F overnight. At this temperature and below, the plants’ growth rate slow, which means stored sugars aren’t used up. As such, they’ll still be high in the early morning. In this situation, potentially at-risk horses should not have pasture access.

And, you must consider that some very sensitive horses might never be able to graze safely, while others can with careful grazing and pasture management. It all depends on the individual horse. Grazing muzzles are a very useful tool to help limit grass intake but still allow pasture access. Studies have shown that some muzzles can limit intake by as much as 80%.

Proper Pasture Management

Another important consideration is that most of the sugar in grasses tends to be in the bottom 3 to 4 inches of the plants. While it might be tempting to think that a very short, overgrazed pasture is safe because there’s “nothing out there,” such pastures present several risks—grasses are very stressed and only the lower inches of the plant are available, meaning these pastures can be very high in sugar.

As such, proper pasture management is very important to keep grasses from becoming stressed. This means horse owners need to properly fertilize and irrigate (if necessary) pastures.

It’s better for the plant and safer for the horse to stop grazing when the pasture has only about 3 to 4 inches of height left. This not only reduces sugar intake by your horse but also leaves some leaf for the plant so that it can regrow without having to dip in to root stores too heavily.

Take-Home Message

With an understanding of pasture grass metabolism and careful pasture and grazing management, many horses should be able to safely graze for at least part of the day. But, always consult your veterinarian or equine nutritionist before turning out your potentially sugar-sensitive horses on pasture.

Two horses in Florida recently tested positive for strangles. The horses live in Charlotte and Walton counties. 

In Charlotte County, a 14-year-old Quarter Horse gelding tested positive on May 20 after developing nasal discharge. He is under quarantine, and one additional horse is suspected positive. 

In Walton County, an 8-year-old Thoroughbred gelding tested positive on May 20 after developing a lymph node abscess on May 15. One additional horse is suspected positive, and four horses are exposed. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

On May 20, a 25-year-old mare at a boarding facility in the Regional Municipality of Halton, Ontario, tested positive for strangles. The mare developed a thick nasal discharge and cough after sharing a paddock with four new horses. She is now under quarantine. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

Six horses at a premises in Los Angeles County, California, recently tested positive for equine herpesvirus-1 (EHV-1). 

Two horses—a 20-year-old Thoroughbred mare and a 28-year-old warmblood mare—were reported positive on May 16. The 20-year-old mare was euthanized, and 95 exposed horses were placed under quarantine. 

Since then, four additional horses have tested positive, including a 3-year-old gelding, a 20-year-old mare, a 21-year-old warmblood mare, and a 24-year-old Quarter Horse mare. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and EHM.

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.

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.

One horse at a stable in Mirabel, Quebec, recently tested positive for equine influenza after developing a cough and light nasal discharge. The horse is under quarantine. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Equine Influenza

Equine influenza is a highly contagious respiratory disease that infects horses, ponies, and other equids, such as donkeys, mules, and zebras. The virus that causes it is spread via saliva and respiratory secretions from infected horses. Horses are commonly exposed via horse-to-horse contact; aerosol transmission from coughing and sneezing; and contact with humans’ contaminated hands, shoes, or clothes or contaminated tack, buckets, or other equipment.

Clinical signs of equine influenza infection can include a high fever (up to 106°F); a dry, hacking cough; depression; weakness; anorexia; serous (watery) nasal discharge; and slightly enlarged lymph nodes. Consider monitoring your horse’s health at shows by taking his temperature daily, which can help you pick up on signs of infection early and take appropriate measures to reduce disease spread.

​Vaccination is an important and inexpensive way to protect your horse. US Equestrian requires proof that horses have had an equine influenza vaccination within the six months prior to attending organization-sanctioned competitions or events. Your veterinarian can help you determine what other vaccines your horse might benefit from.

In addition to vaccinating, following strict biosecurity protocols can help reduce your horse’s chance of infection and disease. Such measures include quarantining new equine arrivals at barns, disinfecting buckets and equipment, and preventing nose-to-nose contact between horses.

One horse at a private facility in King County, Washington, recently tested positive for pigeon fever. No additional details are currently available. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Pigeon Fever

Pigeon fever is a bacterial infection that affects cattle and horses. It can cause large abscesses, most commonly on the chest and under the belly. Horses become infected when bacteria enters through broken skin, such as small scrapes or wounds. Peak season for infection is late summer through fall.

Good horse health safety practices are key to limiting the spread of pigeon fever. These practices include:

• Fly control;
• Not sharing water buckets or equipment; and
• Avoiding tying horses in high-traffic areas.

If a horse owner suspects that their animal is affected, they should contact their veterinarian.

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.

People say good school horses are worth their weight in gold. Here’s what it takes to maintain the equine industry’s most valuable teachers.

How do you preserve your school horses’ health, soundness, and well-being long-term? This difficult question challenges every good horseman, says Jesslyn Bryk-Lucy, DVM, cAVCA, professor of equine studies and resident veterinarian at Centenary University, in Long Valley, New Jersey, where she manages the daily medical needs of the school’s approximately 85-horse herd.

Riding school owners like Nina Leeds, who runs Manor Hill Farm in Nicholson, Pennsylvania, constantly face the challenge of balancing their ponies’ and horses’ health and welfare with the financial pressures of their business. “You must do right by your equine employees,” she says.

Let’s take a closer look at the challenges and unique needs of riding school mounts.

School Horses’ Unique Challenges

Unlike a privately owned pleasure horse that’s not expected to pay for himself, school horses must earn their keep, generating enough income to cover their own care. But despite widespread stigma, a riding school job doesn’t necessarily equal subpar access to equine health care. In Bryk-Lucy’s collegiate program, where horses train and compete in the hunter/jumper and dressage disciplines, these equine professors have access to top-of-the-line care—a prime example being regular chiropractic and acupuncture treatments.

Nonetheless, these animals deal with stressors specific to their school horse status. “Inconsistency of riders is undoubtedly the biggest challenge,” Leeds admits. “These individuals must be forgiving and adaptable. Most of the time their student riders are still working on the basics and, as a result, may unintentionally sit crooked, add more pressure to one rein than another, etc.,” she says. “This can be habit-forming for the horses, causing them to travel incorrectly and creating compensatory pain over time.”

Adding to the challenge, she says, most ponies get ridden by children of varying skill levels because small, light, and experienced adult riders are hard to find.

Different Jobs, Similar Needs

Despite their occupational challenges, school horses have the same physiological needs as any other horse. “I manage the 85 school horses like any privately owned horse in my ambulatory practice,” says Bryk-Lucy, who also owns Leg Up Equine Veterinary Services in northern New Jersey. “The issues that I often have to manage—arthritis, sore backs, chronic soft tissue injuries, navicular syndrome, etc.—are the same pathologies (disease/damage) I see in private practice.”

Starting with the basics, school horses need suitable forage-based nutrition, sufficient turnout, proper grooming, regular dentistry and hoof care, and appropriate vaccination and deworming. In 2021 Bryk-Lucy’s then-student Abigail Reilly found that university horses turned out for at least 12 hours a day had a 25% lower incidence of soft tissue injuries than those turned out for less time¹. Researchers on a French study looking at 184 school horses found housing had the biggest impact on the animals’ emotionality level, a factor affecting their suitability to teach riders of varying levels². The data underscore the importance of species-appropriate care, including turnout and social contact for school horses.

Recognizing Signs of Pain in School Horses

Many school horses are hardy and stoic, making it easy to overlook signs of distress and discomfort. Pain can also manifest in subtle ways, which is why Bryk-Lucy relies on the staff and students to alert her to any potential issue with a university-owned horse. In her experience, early detection can have a significant positive effect on the horse’s recovery.

“Some common complaints that prompt an exam are an evasive response suggesting back soreness when being brushed, crabbiness when grooming and tacking, mounting block issues, reluctance to move forward, refusing jumps, favoring a lead, swapping (leads) before a jump, missing a lead change, running on the landing of a jump, tripping, etc.,” she says.

“In our lesson program we try to rule out pain as a cause of the behavior before classifying that behavior as a training issue,” she adds. In another study, the same French authors mentioned earlier found school horses were less likely to exhibit back disorders if managed by attentive caretakers who tend to overevaluate potential back pain³.

Essentially, scientists have shown attention to subtle changes in horses’ demeanors and getting the vet involved early pays off.

Limitations And Expectations

“Like most riding school programs, we have quite a few ponies that come to us as a step-down job from their competition careers with preexisting limitations,” Leeds says. She credits their long-term success to resisting the urge to push these schoolmasters when they are seemingly going so well.

“If our veterinarian has advised us that a pony should be used for flatwork only, not be longed, etc., there are no exceptions for us,” she adds. “It’s tempting when you are in a pinch, but ultimately pushing them past what is advisable, even as a once-in-a-while exception to the rule, can be detrimental to the goal of a long, productive career.”

Leeds says she’s found that teaching true horsemanship helps minimize wear on her ponies while still allowing her to run a large, successful program. Here again, setting expectations and prioritizing horse welfare remain key. “My students do not expect to jump every day, jump huge fences, or ride in extreme temperatures,” she says. “Our goal is to teach them that the animal must always come first. In turn, we can provide a more realistic workload for the lesson ponies.”

Further, Leeds emphasizes correct flatwork and small jumps with more technical exercises, and she turns to activities such as groundwork sessions and trail rides on extremely hot or cold days. For both their physical and mental well-being, she’s found it helpful to introduce variety in school horses’ work while limiting longe-line lessons because repeatedly traveling in circles adds strain to the musculoskeletal system.⁴

Money Matters

The stakes are high for the barn owner who depends on lesson income to feed and care for all her in-work, laid-up, and retired school horses and pay for and maintain the property. In France students often purchase an annual riding school pass with a fee to fund the school horses’ retirements. In the U.S. some establishments are switching from a no-commitment pay-per-lesson billing method to a semester-long subscription system, eliminating the sometimes devastating unpredictability of fluctuating monthly income. Some early adopters of the practice point out that school horses need to eat regardless of whether students attend their scheduled sessions.

We turned to Bryk-Lucy to describe the common physical limitations of school horses. “Beyond soft tissue and joint injuries, I see a lot of back soreness,” she says, pointing out that these animals typically carry different saddles and riders daily. Under her care university horses with chronic back pain get their own saddles. The rest get time off, non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone (Bute) or firocoxib, methocarbamol (a muscle relaxer), acupuncture, and chiropractic care. “These individuals usually return to work and are monitored and managed closely,” she says. However, if one needs shock wave therapy or regenerative therapies, she must refer to an outside practice, which she says isn’t always cost-effective for such a large herd.

Beyond her own expectations, Bryk-Lucy must also manage those of the faculty, staff, and students. “The reality is these donated horses are on their second or third career; they may come to us with a stiff hind end, good and bad days, etc.,” she says. As long as horses are comfortable and willing to work,and the slight gait abnormality (also called a mechanical lameness) does not worsen, she allows them to keep doing their job.

“I prepare the faculty, staff, and students to expect these individual variations in certain horses and educate them on what to look for to identify a new or worsening condition,” she says. There’s an upside, though. “Sometimes soundness issues in a low-level riding program are not as limiting as they once were on the show circuit because the horses are doing an easier job, and then I don’t have to manage anything!”

What Makes or Breaks School Horse Soundness

Bryk-Lucy says some of the big considerations that affect school horses’ ability to stay sound for the long haul include:

• Limiting rider weight to no more than 20% of the school horse’s body weight, because researchers have found exceeding this can temporarily cause lameness⁵.
• Maintaining fitness. Researchers have shown hippotherapy horses better tolerate heavier riders when fi tter⁶. “Fit horses are better able to handle their workload and less likely to sustain a soft tissue injury,” Bryk-Lucy says. “Some of our university horses are off for the summer and winter breaks. We are very careful and strategic with their return to work to ensure they are fi t enough for the first intercollegiate horse show, generally four to six weeks after the start of the semester.”
• Imposing limits on how often and how high horses jump. In a 2010 study of eight school horses, researchers in the Netherlands confirmed via blood tests what professionals already knew—jumping, even at a low level, significantly increases workload compared to cantering the same distance and speed without jumps⁷.
• Scheduling lessons so school horses have rest days and time off to recover. In 2023 researchers published data suggesting that following an increase in work hours, school horses show a greater degree of behaviors that can be interpreted as either fatigue or discomfort using the Horse Grimace Scale (HGS)⁸. Trainers must provide proper recuperation time to support career longevity.
• Choosing the appropriate level for use in a riding program, considering previous injuries, age, soundness, and suitability. “The horses that successfully work for a long time start at upper levels and slowly teach less experienced riders as they age (and need to step down),” Bryk-Lucy says. “These horses can continue to earn their keep as they age gracefully, fulfilling multiple roles as their career progresses.”
• Keeping up with maintenance as needed and addressing health and soundness issues early. At Manor Hill Leeds’ vet evaluates her ponies at least twice a year when it’s spring and fall vaccination time.

Leeds has found workload to be the most significant factor affecting a school horse’s career longevity. “Overloading an individual with a jampacked schedule risks leaving them physically sore and mentally burnt out,” she says. “Being realistic about how many students you can take with your current lesson stock is important,” she adds, tying back to the importance of keeping expectations in check.

“Pushing your lesson horses beyond reasonable risks harms both your animals and your means of making an income, potentially resulting in horses needing significant downtime and incurring vet bills,” she adds. To find the right balance, she grew her program gradually, accepting more students only as she could find more ponies to join her team.

Final Thoughts on School Horse Soundness

People say good school horses—reliable, adaptable, forgiving, and sure-footed—are worth their weight in gold. Our sources establish a few truths about the noble fourlegged teachers in riding schools: They need to earn their keep. They are athletes and should be treated accordingly, and they face unique challenges tied to their occupation. Ultimately, school horses form the foundation of our equestrian sport and deserve our commitment to a lifetime of care.

References

1. Reilly AC and Bryk-Lucy JA. Incidence of soft tissue injury and hours of daily paddock turnout in non-elite performance horses. 2021 Equine Science Society Virtual Symposium. tinyurl.com/6z75a9mw

2. Lesimple C, Fureix C, LeScolan N, Richard-Yris MA, Hausberger M. Housing conditions and breed are associated with emotionality and cognitive abilities in riding school horses. Appl Anim Behav Sci. 2011;129(2-4):92-99.

3. Lesimple C, Fureix C, Biquand V, et al. Comparison of clinical examinations of back disorders and humans’ evaluation of back pain in riding school horses. BMC Vet Res. 2013;9:209.

4. Logan AA, Nielsen BD, Robison CI, Hallock DB, Manfredi JM, Hiney KM, Buskirk DD, Popovich JM. Impact of gait and diameter during circular exercise on front hoof area, vertical force, and pressure in mature horses. Animals. 2021;11(12):3581.

5. Dyson S, Ellis AD, Mackechnie-Guire R, Douglas J, Bondi A, Harris P. The influence of rider: horse bodyweight ratio and rider-horse-saddle fit on equine gait and behaviour: a pilot study. Equine Vet Educ. 2020;32(10):527-539.

6. De Oliveira K, Clayton HM, Dos Santos Harada É. Gymnastic training of hippotherapy horses benefits gait quality when ridden by riders with different body weights. J Equine Vet Sci. 2020;94:103248.

7. Sloet Van Oldruitenborgh-Oosterbaan MM, Spierenburg AJ. The workload of ridingschool horses during jumping. Equine Vet J. 2006;38(S36):93-97.

8. Ijichi C, Wilkinson A, Riva MG, Sobrero L, Dalla Costa E. Work it out: investigating the effect of workload on discomfort and stress physiology of riding school horses. Appl Anim Behav Sci. 2023;267:106054.

This article is from the Older Horse 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.

Weighing Benefits Versus Risks

To boot or not to boot? The choice to cover a horse’s legs—and with what—­depends on many factors unique to each horse.

A main consideration is whether the horse has a specific need for protection, says Marlin, based on a previous injury, for example. Maybe he’s had issues with overreach and clips his forelimbs with his hind limbs. Or she’s got scrapes on the inner fetlocks where the opposite foot strikes. “If that shoe hits the inner fetlock just right, you can get a chip fracture,” he says.

Horses at high risk of colliding with structures other than their own feet—such as cross-country obstacles or show jumping fences taken at high speeds—also need protection. Horses hacking out through thick brush or on rocky paths need boots, at the very least to protect their skin from injury.

Hill believes it makes sense to follow the lead provided in human sports. “Human athletes use compression sleeves, tape, or braces to provide some support to areas that are unstable or a source of chronic issues, and I don’t recall those applications being shown to their detriment,” he says. Horses with chronic issues might still be able to have active careers with a bit of leg support, he says, and wrapping could help stabilize more recent injuries while they heal.

Warning Signs

Our sources agree: When used correctly, boots and wraps should only help, not harm. While researchers are still working on practical recommendations for their use, riders can take precautions to ensure these pieces of equipment aren’t causing new problems.

Polo wraps must be applied with just the right amount of tension—a skill riders can learn from experienced horse people, veterinarians, or physical therapists, says Hill. Any inflammation or swelling could suggest the wrap was too tight, he says.

Wet wraps might lose elasticity and trap moisture, putting the horse at risk of dermatitis (skin inflammation), Hill adds. Never apply a wet wrap. If the wrap gets wet during exercise, riders can complete the session, remove the wrap, and dry the leg.

As for boots, they shouldn’t slip, but they also shouldn’t be overtight, says Marlin. “Try putting an ankle bandage on, and make it really tight over your Achilles tendon,” Marlin says. “Then go for a run and see how that feels. You won’t do it to your horse again.”

Riders must also consider external factors, he adds. “The hotter the weather, the thicker the boot (especially foam or fleece types), the harder or longer the exercise, the hotter the tendons are going to get,” Marlin says.

Take-Home Message

Riders often apply boots and wraps to their horses’ legs for protection. But science still struggles to support manufacturers’ claims that boots and wraps help prevent certain injuries, and some researchers suggest they might increase the risk of tendon injury. Until evidence provides clearer guidelines, riders can aim to use properly applied boots and wraps wisely, recognizing their potential benefits and risks.

Editor’s note: This article was originally published in the Riding Horse 2023 issue.

Biosecurity measures remain a critical component to combating ‘strep throat for horses’

Teddy and the Chipmunks were brand-new additions at FarmHouse Fresh Sanctuary, in McKinney, Texas. The 15-month-old donkey and his three Miniature Horse friends were quarantined for the sanctuary’s standard 30-day period in the summer of 2023. On Day 29, feeling relieved that quarantine for Teddy and the Chipmunks was ending, the sanctuary’s team started removing the temporary fences that keep quarantined herds from touching noses with healthy resident animals.

On Day 30 the newbie herd started showing signs of equine strangles.

Strangles has been vexing horse owners since at least 1256. Caused by the bacterium Streptococcus equi, the common name “strangles” refers to the upper respiratory noise that is one of the disease’s more remarkable clinical signs. It ranks among the frequently encountered infectious diseases affecting horses.

Equine strangles is an old problem, but when it’s happening to your herd, it can feel dramatically new, changing your daily routines in an instant.

“We went on strict lockdown with them,” recalls Elise Khan, manager of the sanctuary. “Only one person would go in with them … once that person finished in the morning, they had to go upstairs and shower and change their clothes.”

Khan’s sanctuary team has been forthcoming online about the strangles outbreak. Khan says the organization’s mission to rescue animals from some of the worst situations puts her and her colleagues in a position to share information.

“It’s usually not somebody’s fault. No one would intentionally spread strangles,” Khan says. “I just feel (with) all these medical things, it would just be really comforting to me to have seen someone else go through it. And understand what to do and how to prevent it.”

‘Strep Throat for Horses’

Although it is caused by a different bacterium, “strep throat for horses” is a suitable analogy for strangles, says Ashley Boyle, DVM, Dipl. ACVIM. Boyle is an associate professor at the University of Pennsylvania New Bolton Center, in Kennett Square, teaching in the field service section. She has been researching strangles for 15 years and was the lead author on the American College of Veterinary Internal Medicine’s 2018 consensus statement regarding strangles.

But where humans can hoarsely complain about their sore throat, horses can’t articulate their discomfort.

“In horses, it gets further along before it’s recognized,” Boyle says.

The earliest sign your horse has strangles is a temperature spike. “A spike would just be an increased temperature from the normal range,” she says, which is typically 99-101.5 F. “Though sick horses are often 103 F or warmer, you should look for an increase in the horse’s normal recorded temperature.”

Other signs include a runny nose, difficulty swallowing, a “strangled” upper respiratory noise, not eating, swollen lymph nodes, or abscesses on the throat or jaw. Authors of the consensus statement report that the abscesses might rupture and drain externally or internally.

The strangles incubation period—the time from exposure to first indications of illness—can be three to 14 days, Boyle says. Once clinical signs start, they can last a few weeks.

While younger horses are more likely to be affected by strangles, S. equi can infect horses of any age. They can be exposed to the bacterium at shows, sales barns, or other places horses commingle.

PCR Testing: The Gold Standard for Equine Strangles

One of the newer developments in strangles detection and management is the use of a PCR (polymerase chain reaction) test. Now considered the “gold standard,” the PCR test can detect S. equi before a culture.

While it’s not “wrong” to test for strangles using a culture, Boyle says, it might miss the infection early on.

“If it’s early in the fever, you may not get a positive right away because they haven’t started shedding (the bacteria),” she says .

Veterinarians also need to test the correct area of the horse’s body. “They’ve heard us harp on checking the guttural pouches (blind-ended sacs on either side of the throat), but that’s actually more when you’re kind of looking to clean up the disease,” Boyle says. “The guttural pouches may not actually be positive early on in the disease.”

At the start, it might be better to get the sample from the nasopharynx (the cavity above the soft palate) via a nasopharyngeal wash or an aspirate of an enlarged lymph node.

“Those can be done with culture or PCR,” she adds. “But if you’re getting negatives and you’re still suspicious of strangles, you really should be checking with PCR.”

What You Need to Know About Guttural Pouches

If a horse has chondroids(firm balls of pus) in his guttural pouches, the S. equi is contagious. “That’s what makes the carriers and what makes the risk of infection keep going even if you have got all the clinical signs down in the herd,” explains Alberte Fridberg, DVM, of the University of Copenhagen’s Department of Veterinary and Animal Science and Ansager Equine Hospital, in Denmark. To look for chondroids in the guttural pouch, your veterinarian will use a scope and flush the area.

When a “persistent carrier” continues to shed the bacteria into common areas like water troughs, a strangles outbreak can seem to be waning, only to flare back up again, making the outbreak last longer.

Equine Strangles Vaccination Strategy

In the U.S. there are two strangles vaccines you need to know about, Boyle says. There is an intramuscular vaccine and an intranasal vaccine.

Both vaccines provide protection against S. equi. A benefit the intranasal vaccine offers is that it provides immunity at the location where bacteria enter the horse, Boyle says. Meanwhile an intramuscular vaccine given to the dam prior to parturition (birth) can provide protection to a suckling foal.

Strangvac, which is available in Europe but was still awaiting USDA approval as of November 2023, has the attention of Fridberg, who was still a veterinary student when strangles captured the attention of Denmark’s horse community during an outbreak. She was inspired to work on an article outlining strangles hygiene, which was ultimately published in 2023 in Equine Veterinary Education.

Fridberg says she finds Strangvac interesting because of its DIVA—differentiating infected from vaccinated animals—capabilities.

“We were missing that in some of the others,” Fridberg says. “That’s an important ability of a vaccine.”

Vaccine timing is important.

If your barn is in the middle of an outbreak, you’ll have to wait before vaccinating, says Boyle. That’s because some horses are hyper-responders and can develop purpura hemorrhagica (an immune-mediated inflammation of blood vessels causing swelling of the belly and limbs and bleeding noted on the gums) after the vaccine. For the same reason, you’ll need to be cautious about vaccinating horses known to have had strangles in the past. Your vet might recommend running a titer to check your horses’ immunity to be sure they aren’t at high risk of being hyper-responders.

Isolating the Sick Herd

When equine strangles strikes, put up the fences. Isolation is key because the bacteria spread through close contact and shared equipment.

“It’s easier said than done,” Boyle acknowledges. “And I so appreciate that. But it’s so, so important.”

Exactly how you’ll isolate your horses will depend on your facilities. On some farms, that might mean the barn becomes the sick ward, and the pastures are for horses without clinical signs. On other farms, that might mean turning a run-in shelter into a stall and adding a double fence perimeter to the shed so horses in the rest of the pasture can’t touch noses with the sick horse.

The team at FarmHouse Fresh Sanctuary, which faced two outbreaks in six months, designated one pasture for healthy horses. The pasture beside it was for sheep on one side and goats and donkeys on the other. The third pasture was for sick horses.

“None of them could touch noses,” Khan says. “The goats can’t get strangles, but let’s say (a sick horse) sneezed and a goat stepped in it and then walked over to a healthy horse. A healthy horse could get it (from coming in contact with the nasal discharge). So that’s why we got really strict.”

Checking Temps, Cleaning Buckets

Once you’ve established your quarantine area, look at hygiene considerations such as shared equipment, temperature checks, and personal protective equipment.

Shared water sources provide an opportunity for exposure to S. equi; each pasture and stall should have its own water source with no cross-contamination—don’t swap out buckets and don’t let a hose dip into the water of any bucket or trough and then dip it in the next.

You’ll need to clean, disinfect, and dry buckets and other shared materials. Don’t skip the drying process.

“The bacteria love wet environments,” Boyle says. “That’s been shown in studies.”

Also, remember the human element. You’re a possible disease “fomite.” The concern isn’t your snot; it’s the snot on your sleeve or slobber from a sick horse, much like the goat scenario Khan described (the goat could’ve acted as a fomite, too).

If you are managing a strangles outbreak, expect to do a lot of laundry. It will be up to you how you manage that; maybe you’ll elect to have personal protective equipment such as Tyvek suits. Maybe you’ll wear different clothing around different herds. Maybe you’ll have different personnel handle sick horses. You might also add a disinfecting foot bath station and hand sanitizer pumps.

For the most part, washing machines work well at killing off the bacteria. But beware of nylon halters. In a Swedish study, researchers found the bacteria survive on nylon halters even after going through the machine, Boyle says. It might be best to throw nylon halters away after sick horses wear them.

Though the long incubation period associated with strangles can be daunting, temperature checks are your best hope.

Catching a jump in temperature can allow you to move the horse to isolation before it starts shedding a lot of bacteria.

“That’s the way to stop the outbreak,” Boyle says.

She recommends twice-daily temperature checks for every horse on the farm during an outbreak, but stresses that making temperature checks a part of your regular horse care routine can make it easier to catch even illnesses besides strangles.

“Anyone who had a fever of over 102.5 degrees would go straight over to the quarantine,” Khan says of the farm’s second outbreak. The team would then clean and sanitize the horse’s stall and equipment. “We also took notes on their discharge from their nose because our vet tells us you’re basically looking for … banana pudding consistency.”

The long battle with strangles has Khan taking a different approach to biosecurity. She’s extended the quarantine period for new additions to 35 days and is adding a pharyngeal wash for testing to new horses’ standard care before being released into the herd.

If your horse comes down with strangles, your veterinarian might or might not recommend antibiotics. It will depend on how sick your horse is. Horses that get antibiotics for strangles might not develop strong immunity to S. equi and could be reinfected, per the 2018 consensus statement.

Take-Home Message

Regularly checking your horse’s temperature can help you catch equine strangles early.

Strategize now for how you will separate infected, exposed, and healthy animals on your property. Build or buy any infrastructure you might need, such as temporary fencing or extra water troughs. Finally, talk to your veterinarian about vaccinating your horse against strangles.

Further Reading

Fridberg, A., Adler, DMT, Jørgensen, M.G. & Olsen, R.H. (2023) The hygienic aspects in the management of strangles. Equine Veterinary Education, 35, 540–550. Available from: https://doi.org/10.1111/eve.13794.

Boyle AG, Timoney JF, Newton JR, Hines MT, Waller AS, Buchanan BR. Streptococcus equi Infections in Horses: Guidelines for Treatment, Control, and Prevention of Strangles-Revised Consensus Statement. J Vet Intern Med. 2018 Mar;32(2):633-647. doi: 10.1111/jvim.15043. Epub 2018 Feb 9. PMID: 29424487; PMCID: PMC5867011.

A 27-year-old Arabian mare at a boarding facility in Dane County, Wisconsin, recently tested positive for strangles after developing clinical signs on May 8. She is under quarantine, and 50 horses are potentially exposed. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.

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.”