Kaydence Sports Medicine & Rehab

01/02/2026

Equine Esophagel Obstruction—Better Known as Choke

Esophageal obstruction, routinely referred to as choke, is considered an equine emergency. It often results from feed or a foreign object getting lodged in the esophagus. Types of feed often associated with choke include hay, grain, and/or beet pulp. However, choking horses can present with a variety of feedstuffs, including treats, as well as nonfeedstuffs (such as wood and shavings). In addition, geriatric horses can be more prone to choke.

When a Horse Chokes
Some causes of choke include: eating quickly (bolting), dental issues (worn or missing teeth, dental disease), foreign objects, dehydration, and recent sedation.

Clinical signs of choke are often associated with the horse’s inability to swallow, leading to a buildup of saliva and feed in the pharynx that often exits through the nostrils. This results in the classic frothy, feed-tinged nasal discharge seen with these cases. Horses can also exhibit signs of pain similar to colic.

Other signs include coughing, stretching out the neck, hypersalivation, agitation, attempting to swallow, inappetance, and a palpable swelling on the left side of the neck.

Treating a Horse for Choke
If you suspect choke, call your vet immediately. The longer an episode continues, the more likely complications could result.

While waiting for your practitioner to arrive, remove feed and water from the stall/pen, and try to keep your horse calm.

Veterinarians often start with a thorough physical exam and then administer sedation. Sedation allows passing of a nasogastric tube; this is the best way to confirm choke. In a nonchoking horse the tube passes from the nostril to the pharynx, into the esophagus, and down to the stomach. With a choking horse the tube stops once it hits the esophageal obstruction. Keeping the horse’s head low during this procedure allows fluid to exit the nostrils and minimizes aspiration.

Next steps typically involve performing a gentle water lavage of the obstruction through the tube. If the choke can’t be relieved in the field, or there is concern about damage to the esophageal mucosa or aspiration pneumonia, your veterinarian might refer your horse to a hospital for an endoscopic exam and ultrasound.

Endoscopy allows practitioners to evaluate the esophageal mucosa for damage or potential secondary complications (such as strictures, etc.). An endoscopic exam also allows visualization of the obstruction’s cause and gives a continued opportunity to relieve it. In cases of potential aspiration pneumonia, the veterinarian will perform a thoracic ultrasound. In a small percentage of cases, horses need general anesthesia or a few days at the hospital to resolve a choke.

Once resolved, practitioners will outline a refeeding schedule and a management plan for your horse.

Preventing Future Choke
Steps you can take to help prevent a future episode include: not feeding following sedation (wait until your horse is awake); using a slow feeder if your horse bolts feed; and ensuring regular veterinary dental care.

Take-Home Message
In a perfect world your horse will not experience choke. But if he does, remember to call your veterinarian as soon as possible to help guide you and your horse through this emergency.

The Horse

12/29/2025

Equine Neurologic Conditions vs. Lameness

While trotting around the arena, you feel your horse stumble behind. He’s done it before, but is it just weakness? A patch of deep footing? Or could it be something more serious such as a neurologic condition? Musculoskeletal and neurologic lameness can be difficult to differentiate, but with a thorough exam and appropriate diagnostics, veterinarians can often determine where the problem lies and how to treat it.

Signs of Neurologic Disease in Horses
One key concept helps guide that process: A neurologic horse’s gait is “irregularly irregular,” while a lame horse’s gait is “regularly irregular,” says Stephen Reed, DVM, Dipl. ACVIM, of Rood & Riddle Equine Hospital in Lexington, Kentucky. A neurologic horse often shows proprioceptive ataxia, meaning poor coordination and reduced awareness of where his limbs are in space. “Ataxia is an abnormal sway of the limb in the air, abnormal posture or positioning when it lands, circumduction when turning in small circles with a wide outward turn with one of the limbs, and pacing.”

These horses might also show signs of weakness, such as tripping, dragging a foot, or stumbling. “Damage to the spinal cord can manifest as spastic or weak limb movements that result in tripping or an abnormal gait that might be mistaken for orthopedic lameness,” says Amy L. Johnson, DVM, Dipl. ACVIM-LAIM, of the University of Pennsylvania’s New Bolton Center, in Kennett Square. “These steps that can look in some ways like a lameness, but it’s not in one leg, it’s in all four legs, so it can be really hard to pinpoint. The horses can feel very ‘off,’ but the rider or the observer can’t pick a leg because each leg is doing something different, and it’s a very irregular gait. There also is often some weakness or buckling that’s common with neurologic disease.”

Typically, a horse experiences musculoskeletal lameness due to pain from an injury site. In contrast, a neurologic horse might not appear painful and, for that reason, a veterinarian might recommend a short phenylbutazone (Bute, a non-steroidal anti-inflammatory drug) trial. Improvement suggests a musculoskeletal cause.

Diagnosing Neurologic Disease in Horses
A standard lameness exam—including hoof testing and nerve blocking progressing up the limb—can help your veterinarian localize pain. Diagnostic imaging such as radiographs, nuclear scintigraphy (bone scans), and ultrasound can help pinpoint the source of pain. “If you get all the way up to the shoulder and you haven’t been able to make the horse normal, you have what I would call an unblockable lameness,” says Reed, pointing toward a possible neurologic cause.

In those cases a veterinarian might proceed with a neurologic exam, which includes walking the horse in a tight circle and in a zigzag pattern, pulling on the tail to assess strength and response, and carefully observing limb placement. If a horse appears incoordinated, has delayed reactions, or leans excessively, those findings raise concern for neurologic disease.

Common Equine Neurologic Diseases
Equine protozoal myeloencephalitis (EPM) affects the spinal cord and causes asymmetric gait abnormalities that can mimic musculoskeletal lameness. The protozoa responsible for EPM can affect multiple areas of the nervous system. “It is not unusual when you have those kinds of infections to also get muscle wasting,” says Reed. “When you have muscle atrophy, the hallmark clinical sign is weakness.”

Johnson also sees horses with an abnormal hind-end gait referred for suspected pelvic fractures after a presumed fall. During sedation, technicians might notice the horse appears wobbly and, after a clean bone scan, a cerebrospinal fluid tap ultimately confirms EPM.

Johnson says some of the most challenging neurologic cases affect only one limb. “Those are ones where you have either peripheral nerve involvement or a specific area of the spinal cord that houses the cell bodies that contribute to the peripheral nerve,” she explains. “When those nerves are affected, the horse develops a gait abnormality localized to one limb; EPM is the most notorious neurologic disease to do that.”

Cervical stenosis, commonly referred to as Wobbler syndrome, can also cause signs of neurologic disease. This developmental condition compresses the spinal cord in the neck, leading to incoordination and ataxia.

Johnson also notes that neck arthritis or a condition called foraminal stenosis can cause nerve compression, pain, or lameness. Foraminal stenosis refers to narrowing of the opening, or foramen, where nerve roots exit the spinal cord and form the spinal nerves that innervate the front limbs. Traumatic nerve injury or even a tumor putting pressure on a nerve can create similar clinical signs.

Diagnosing Equine Neurologic Conditions With Technology
Johnson says veterinarians have growing interest in objective ways to identify mild ataxia because diagnosis currently relies heavily on subjective assessment. Scientists are examining electrodiagnostic techniques that measure signal delays between the brain and limbs—particularly through the neck region—though they are not yet widely available. “There is a potential means to put a number on things and document that it truly is a spinal cord problem,” she says. “That type of electrodiagnostic technology is being actively investigated to assist in both the differentiation and quantitation of neurologic disease to determine whether the spinal cord is transmitting information correctly and, if not, how slowly it’s functioning.”

Artificial-intelligence-powered equine gait analysis apps already detect asymmetry and provide stride-by-stride data, and Johnson says they could eventually support neurologic assessment as well. “It’s just because of the irregularity and the unpredictability of the neurologic gait that it hasn’t been as easy to use this type of AI compared to its routine use for a lameness that’s more consistent,” she explains

Electrodiagnostic testing to evaluate muscle and nerve function, such as transcranial electrical and transcranial magnetic stimulation, represents another sophisticated diagnostic tool, Reed adds. “But that’s going to be something that’s done to each individual horse, as opposed to something that you would look at and utilize when trying to assess a gait, say during an exam,” he notes. “This would be an ancillary test you do after the exam.”

Take-Home Message
Pain-related and neurologic gait abnormalities often look similar, but a veterinarian can usually sort them out with a careful exam. As emerging tools such as AI-based gait analysis advance, they might further support diagnostic decision-making. Reed says owners should remember an irregularly irregular gait often reflects neurologic disease, while a regularly irregular pattern typically indicates a musculoskeletal cause.

The Horse

12/20/2025

12/19/2025

Conditioning Horses in Fall and Winter

Fall can bring a welcome relief from blistering heat, but as winter approaches, with freezing temperatures and shortened daylight hours, conditioning horses in fall and winter can become a challenge. In many parts of the country, bitter cold and drifting snow can ruin even the most determined rider’s plan. While you can’t control the weather, with a little knowledge and planning, the colder months can be a safe and productive time for you and your horse.

The challenges of conditioning horses in fall and winter will, of course, vary greatly depending on where you live. In parts of Texas, for instance, winter consists of a few weeks of rain and 50°F temperatures. Similarly, riders in many Southern states might look forward to winter as the “good” time of year to ride, when the likelihood of heat stroke and sunburn wanes. Riders in other parts of the country, however, face a variety of adverse conditions in the form of subfreezing temperatures, gusting winds, extreme dryness or humidity, freezing rain, and snow. Much of the challenge for riders during these months is simply to stay warm and prevent frostbite.

Horses, on the other hand, are fairly well-equipped to handle the cold. Problems can arise, though, when we ask our horses to perform strenuous activities under these circumstances. In the following sections we’ll discuss how cold weather riding conditions affect your horse’s body and what you can do to keep him healthy and performing at his best all season long.

How Your Horse Handles Cold
As with any other management or training change, your horse’s body needs time to adjust to cold weather. While these physiologic adaptations aren’t as extensive as those seen with warm weather riding, it’s still important to give him about two weeks to get used to his new working environment (i.e., if the temperatures have dropped abruptly or you’ve relocated to a colder climate). Just as importantly, there are limits to the ways in which your horse can compensate for the cold; this means that you’ll have to adjust your workouts to accommodate his needs.

Muscles
Cold weather, especially when it’s extreme, can decrease not only skin temperature but also muscle temperature. Numerous studies involving human athletes have revealed that this decrease in muscle temperature can have a detrimental effect on performance for a number of reasons. For example, the contractile structures within the muscle fibers (which are responsible for muscle movement) don’t cycle as quickly when it’s cold. Nerves supplying the muscle also don’t fire as rapidly, and blood flow to resting muscle decreases to minimize heat loss (blood flow is concentrated in the body’s core to keep the vital organs warm). In addition, cold muscles are stiffer biomechanically than warm muscles. All these factors combined result in reduced human athletic performance. Results from one study in humans conducted in the cold estimated that muscle performance is altered 2-5% for each degree Celsius change in muscle temperature. In fact, the people in this study had to walk briskly for 20 minutes before their muscles even warmed up enough to let them perform at a normal level. Although similar studies have yet to be conducted in horses, it’s reasonable to expect that cold temperatures might cause similar reductions in equine performance.

Another important effect of cold is it changes the way groups of muscles work together. Every time a muscle contracts, there is also a small contraction of an antagonist muscle to oppose it; this allows a very fine level of control and lets us make precise movements that are appropriate in speed and strength to the task at hand. When muscles are cold, antagonist muscles might be activated more, and this decreases the net amount of movement and changes the way an exercising horse moves.

As an example, in one study applying cold water up to the knees of human athletes prior to each performing a jump changed the kinematics (or the way that the body moves as a whole) of their jumps. This resulted in decreased shock absorption upon landing. Although these are the results of only one human study, they are important because they suggest that cold muscles might change the kinematics of jumping horses, too. This could be one more reason why horses (especially jumpers) that are not properly warmed up are more prone to injury.

Bones and Joints
How chilly weather affects your horse’s movement depends partially on changes in muscle contraction and partially on these temperatures’ direct impact on the joints. Cold temperatures increase viscosity (thickness) of synovial fluid, making joints feel stiff to the horse. Synovial fluid is thixotropic, meaning that it becomes less viscous when agitated. Thus, joints need to “warm up” before a workout just like muscles do, particularly when it’s cold outside.

Cardiovascular System
When exercising in the heat, one of the primary challenges is to maintain enough blood flow to exercising muscles and the skin so they can help dissipate heat. Training in the cold, on the other hand, causes vasoconstriction in the skin that diverts more blood flow to working muscle. For this reason, horses can often exercise at lower heart rates in cooler temperatures than they can in the heat; in such instances the cold weather actually works in your favor. Just be aware that this decreased blood flow to the skin increases the risk of frostbite, especially if you’re riding with a significant wind chill. Fortunately, healthy adult horses are fairly resistant to frostbite, although riders should be sure to protect their own skin in cold weather. In humans, frostbite of the fingers and toes is prevented by a temporary increase in blood flow every few minutes, which warms the tissue back up. This is improved by exercise training and suggests that the more fit you are, the less likely you might be to get frostbite while riding.

Respiratory System
In both humans and horses, cold weather workouts might lead to exercise-induced bronchospasm (EIB). In humans this is also called “ski asthma,” and it can cause shortness of breath, coughing, and decreased athletic performance. In certain exercising horses researchers believe the upper airways can’t warm and humidify inhaled air quickly enough to prevent exposing the sensitive lower airways to cold, dry air, which causes tissue damage. Just one bout of exercise while breathing cold air can cause lung inflammation and an increased airway resistance to air flow in healthy horses with no history of breathing problems, according to a series of studies published by Michael S. Davis, DVM, PhD, Dipl. ACVIM, professor and director of the Comparative Exercise Physiology Laboratory at Oklahoma State University’s College of Veterinary Medicine, in 2006 and 2007. Surprisingly, these effects can last up to 48 hours after exercise, which could lead to chronic low-grade inflammation in horses that are exercised regularly in the cold. No conclusive evidence exists, however, demonstrating EIB occurs in horses. But as a preventive measure, try to ride in a well-ventilated indoor arena when possible.

Keys to Cold Weather Riding

Warm and Dry
As your mother always said, dressing in layers is the key to staying warm and dry in the winter. Believe it or not, the same is true for your horse. All clipping and blanketing strategies have one goal in common: to keep your horse warm while still allowing his coat to dry quickly after a workout. One strategy is to use a half-sheet or exercise sheet during warm-up and cool-down. This warms the large hip and thigh muscles and aids in the warming process (see the prior section regarding muscles and tendons). Other than the possible addition of an exercise sheet, a winter warm-up shouldn’t differ much from a summer warm-up. A standard recommendation is five minutes each of walking, trotting/jogging, and cantering/loping before really putting your horse to work. After your ride is over, a wool cooler will help keep your horse warm while wicking moisture from his coat. No matter what, your horse should be cool and dry before he is stalled or turned out again.

Clear the Air
If you have a choice of whether to ride indoors or outdoors, consider not only your comfort but also your horse’s comfort. Results from a study done at Pennsylvania State University showed that during the winter there are significant differences in air quality between indoor and outdoor riding arenas. The researchers determined that indoor arenas were slightly warmer than outdoor arenas but were also more humid, likely due to the water applied to arena surfaces to reduce dust. Warm and humid air could help alleviate some respiratory problems, but it also promotes the growth of mold and fungus, which can irritate the lungs. Alternatively, dust can be a major problem, particularly in poorly ventilated arenas.

To improve your indoor arena’s air quality, Jenifer Nadeau, MS, PhD, an equine extension specialist at the University of Connecticut, recommends making sure it is well-ventilated rather than closed up tight.

In addition, if you add water to your arena to keep the dust down, water heavily but seldom. A good rule of thumb is to apply water until the footing has been saturated to a depth of two inches. “You can also consider using products such as salts of calcium chloride or magnesium chloride (for dust control), although both can dry out horse’s hooves,” Nadeau adds.

Good ventilation in the stable area is important as well, since many horses spend more time stabled during colder months. Nadeau suggests turning horses out while their stalls are being cleaned to avoid exposing them to airborne dust and dirt. Also consider ammonia. A quick way to judge air quality in your horse’s living space is to “go into the stall and put your head down to about horse’s nose level,” says Nadeau. “If you smell ammonia, the stall does not have good air quality.”

A “stuffy” feeling might also indicate that the stall needs more ventilation. These problems can often be fixed by opening doors or windows on opposite sides of the barn that allow efficient cross ventilation. “If condensation occurs on surfaces inside the barn, the stable is not being properly ventilated,” Nadeau says.

While it might not seem like it, these small changes can have a large impact on your horse’s comfort, health, and performance.

Safety First
Although frigid temperatures are the more obvious limitation during this time of year, late fall and the winter present additional potential problems for horses and riders. Shorter days mean fewer daylight hours for riding, which can mean increased danger for equestrians who must ride on public roads to access their favorite trail, arena, or cross-country course. Nadeau suggests wearing a reflective safety vest, carrying a light, and riding at a slow pace if you find yourself on the road after dark. “You can even get a safety vest for the neck (and chest) of your horse to make him visible to traffic,” she says.

Another major concern while riding outdoors during the colder months is the footing. Deep snow, hidden ice, and even frozen mud can cause injuries. “A little slip could mean a long layup, so proper shoeing for winter trail rides and removal of ice balls through the use of ‘snowball pads‘ or borium (to prevent slipping) is the best way to prevent injuries,” Nadeau advises. Although it can be frustrating to have to skip a ride, “If it seems dangerous to ride outside, then don’t.”

Take-Home Message
Cold weather presents unique challenges, but with a little knowledge and planning, this time of year can be safe, comfortable, and productive for you and your horse. You mount will also be in better physical condition going into the spring riding and showing season. Be sure to give your horse plenty of time to warm up at the start of exercise, make sure he stays warm and dry, and keep his environment well-ventilated. And, as always, use your best judgment when it comes to you and your horse’s safety.

The Horse

12/17/2025

How to Keep Your Horse Hydrated During the Winter

As we head into an incredibly cold stretch of weather for the start of winter, there has been much discussion on how to prepare horses. Increasing forage intake to help keep core body temperature warm while it ferments in the digestive tract is incredibly important. Also consider providing blankets and shelter, depending on your horse’s hair coat.

One factor we cannot overlook, however, is keeping horses hydrated. Most equine nutritionists consider water to be the most important nutrient because of the various functions it performs. These include regulating body temperature, digestion, absorption, and utilization of nutrients, moving feedstuffs through the digestive tract from mouth to re**um, and removing waste products.

How Much Water Does My Horse Need?
On average, the adult horse drinks approximately 1 gallon per 100 pounds of body weight; therefore, the average 1,000-pound horse needs about 10 gallons of water a day. It is very important to make sure horses are consuming enough water, especially when their diets are high in dry feed content, such as hay, to help ensure the feed is moving through the digestive system. If horses do not consume an adequate amount of water, they may become dehydrated quickly, could go off their feed, and might suffer from impaction colic.

Many horses decrease their water intake below required amounts in extremely cold weather for a variety of reasons, such as not wanting or being able to walk to a water source, water being too cold to drink (preferred water temperature is between 45 and 65 degrees F for most horses), or water being frozen.

Preventing Dehydration This Winter
Horse owners and managers can do several things to ensure their horses do not become dehydrated:

* If a drop in temperature is predicted, make sure water is freely available before the temperature change, so horses are properly hydrated before the cold weather hits.
* If hot water is not available in the barn, get insulated water jugs and bring it from the house. Invest in heated water buckets or a water heater. Make sure these are grounded, and routinely check to make sure they are working properly. A horse that gets shocked when he tries to drink will be conditioned to not drink!
* Break ice if it forms on the water source, and remove the chunks of ice. Although horses can break through thin ice, it can deter them from drinking. “Frost-free” type waterers can be helpful, but even these can freeze if horses are not drinking often enough. Check water sources for ice at least twice a day and more often in colder conditions.
* Monitor your horse’s hydration status daily. If you do not know how, ask your veterinarian or another experienced horse person to train you in doing skin pinch tests and evaluating mucous membranes.
* Soaking feeds can be a way to get additional water into your horse. For example, beet pulp is a feed that can hold a good amount of water, and most horses are willing to eat it. Chopped hays also absorb water and are usually willingly consumed by horses. Ideally, soak these dry feeds in warm water for about 15 minutes before offering them to the horse.

Take-Home Message
When the temperatures drop, make sure water is accessible at all times, and that horses are drinking enough. It is crucial to have water available at mealtimes, especially when feeding dry feeds; researchers have shown that horses drink the most water within three hours of consuming a meal. Finally, carefully monitor both water intake and hydration status daily, especially during extreme or rapid changes in the weather.

The Horse

12/16/2025

Haul in opportunity Friday 12/19 in Rogersville, MO; we are accepting all appointment types.

-general wellness/vaccines
-dental floats
-chiropractic/acupuncture
-lameness/joint injections

Mobile x ray, ultrasound, laser, shockwave, and prostride

Text clinic to schedule 417-448-0131

12/16/2025

We will be at Longhorn Arena 12/18 and are accepting all appointment types.

-general wellness/vaccines
-dental floats
-chiropractic/acupuncture
-lameness/joint injections

Mobile x ray, ultrasound, laser, shockwave, and prostride

Text clinic to schedule 417-448-0131

12/12/2025

Equine dental plaque is a sticky film of bacteria, food, and saliva that forms on horse teeth, hardening into tartar, leading to gum disease (gingivitis, periodontitis), cavities, and oral infections if left unchecked.

When getting your horses annual dental float done, removing the plaque from their canine teeth is part of the procedure!

It is important to have the plaque chipped off as well as an incredibly rewarding activity to watch it all crumble!

Some collect plaque quicker than others, that is why it is something that gets checked annually with the dental float itself. It is important to get it removed so it doesn’t cause further damage to the canine teeth.

A very simple, easy crunch of the pliers tends to remove the plaque quickly and cause no discomfort to the horse.

12/10/2025

Here is some of our upcoming availability.

12/12- available clinic appointments in Carthage - any type of appointment

12/18- appointments available at Longhorn Arena in Mt. Vernon - any type of appointment

12/19- appointments available at the clinic or for farm calls - any type of appointment

Please text the clinic to schedule 417-448-0131

We will have very limited availability between Christmas and new years.

12/08/2025

The Mysterious Fever of Unknown Origin

He’s just a little off. It’s hard to say exactly what’s going on. But he’s your horse, and you know him so well you pick up on the slightest little nuances when something is wrong.

So, you check him all over: no signs of injury, no strange bug bites, no drainage coming out of the nose, no diarrhea, no cough. Then you take his temperature.

Sure enough, fever. Something is wrong. But what?

Welcome to the world of fever of unknown origin. For both owners and their treating veterinarians, this condition can be fraught with frustration, confusion, guesswork, and a Sherlock-Holmes-like investigative process with some modern technological flair.

Fortunately, through strong collaborations with laboratories and referral clinics, horses with fevers of unknown origin can often get the diagnoses and targeted treatment they need.

“At first, it’s unknown origin—but we hope to give it an origin, and give that horse a diagnosis,” says Toby Pinn-Woodcock, DVM, Dipl. ACVIM, assistant clinical professor in the Department of Population Medicine and Diagnostic Sciences at Cornell University College of Veterinary Medicine, in Ithaca, New York.

Understanding Fever in Horses
More than ever, horse owners are tracking their horses’ body temperatures, our sources say.

Technology has certainly played a role in that—thanks to rubbery digital thermometers that beep with a digital reading less than 30 seconds after being inserted in the horse’s re**um. Veterinarians can also now implant microchips with temperature sensors into a horse’s neck, which send real-time data to mobile phones and alert you if the temperature is abnormal.

When such technology meets the hands of highly observant owners, fevers get noticed right away. “Horse owners are so astute,” Pinn-Woodcock says. “They catch things so early—sometimes before there are other signs.”

Re**al or chip-based temperature readings above 101.5 degrees Farenheit (38.5 degrees Celsius) generally indicate a fever in horses. Unless extenuating circumstances exist—such as excessively high outdoor temperatures or significant muscular effort akin to race training—that means there’s some sort of inflammation in the body, says Julia Felippe, MedVet, MS, PhD, Dipl. ACVIM, professor and immunologist in the section of Large Animal Medicine, also at Cornell.

Fever and inflammation function as the body’s first-line defense mechanisms in response to a wide range of health challenges, she says. Specialized molecules induce fever to help immune cells move and function better, while also creating an unfavorable environment for pathogens (disease-causing organisms) to survive.

Indeed, sometimes owners catch fevers before other clinical signs develop, such as nasal discharge, coughing, or diarrhea. Those additional signs often help pinpoint the fever’s cause within a few days, our sources say. But not all horses develop additional signs, even in the case of infectious diseases.

If an acute fever goes away on its own and stays away, it’s still useful to find out its cause—not only to keep the horse’s medical history current and accurate but also determine whether the fever stems from a contagious disease.

But if fevers persist, or come and go, without any clear reason, Pinn-Woodcock recommends finding out what’s behind them, because they can indicate life-threatening diseases.

First Things First: Biosecurity at the Farm

Until you can prove otherwise, assume any fever of unknown origin might stem from a pathogen that could spread to other horses. That means you need to ramp up biosecurity immediately.

Your feverish horse should go in an isolated stall or paddock where he has no contact and shares neither air space nor water sources with other horses, our sources say. “The next step is to contact your veterinarian for evaluation and advice,” says Felippe. If you get a diagnosis for an infectious disease, you’ll need to follow the biosecurity guidelines specific for that disease to prevent or stop an outbreak.

Keep the horse in isolation while you work with your veterinarian to rule out contagious causes of equine fever common to your region, Pinn-Woodcock says.

Causes of Fever in Horses
A feverish horse could have a wide range of bacterial or viral infections, such as strangles, equine herpesvirus types 1 and 4 (EHV-1 and EHV-4), the tickborne disease anaplasmosis (caused by Anaplasma phagocytophilum bacteria), and equine coronavirus—which are a few of the common culprits, our sources say. But they could also carry fungal or parasitic infections such as guttural pouch mycosis and piroplasmosis. Noninfectious conditions, including cancer, immune-mediated disease, or an immunodeficiency disorder, could also be to blame.

“It can be quite challenging to find the cause of fever,” Felippe says.

Cornell’s Animal Health Diagnostic Center (AHDC) offers a comprehensive plan for homing in on horses’ fevers of unknown origin in more complex cases, says Pinn-Woodcock. The Cornell AHDC provides a long list of possible causes of equine fever and diagnostic tests that can be tailored to specific circumstances. These include cultures and polymerase chain reaction (PCR) tests on whole blood, nasal swabs, cerebrospinal fluid, peritoneal (abdominal) fluid, urine, and f***s for pathogens such as herpesviruses, West Nile virus, coronavirus, adenovirus, strangles, Salmonella, Lawsonia, Leptospira, and more.

That doesn’t mean people should run all these tests, she says. Rather, the comprehensive plan serves as a “brainstorming tool” for practitioners. “It’s kind of a jumping-off point to select tests a la carte given the context of each case,” she explains.

Clues for Fever: Seasons, Regions, and Travel
The hunt for a fever’s origin starts with certain clues, our sources say.

Seasons, for example, play an important role, notes Pinn-Woodcock. “We tend to see more fevers caused by betacoronavirus in the winter months, as this virus survives best in cool, moist environments, and we tend to see respiratory viruses in the early spring, which may be due to increased horse travel during this time of year,” she says.

Region also plays an important role, she explains, especially regarding vector-borne diseases. Vectors are disease transmitters—think ticks and midges. Different regions of the world have different vectors. In the northeastern U.S., for example, equine granulocytic anaplasmosis commonly causes fever in horses—especially in the fall when the ticks carrying A. phagocytophilumbacteria are more prone to bite large mammals. And Potomac horse fever, caused by the Neorickettsia risticiibacteria harbored by aquatic insects such as mayflies and caddisflies, occurs most often in summer to early fall in horses living in proximity to a lake, pond, or river in some regions of the U.S. and Canada. Eastern equine encephalitis (EEE) can cause fever in southeastern and Gulf coast states year-round and in northeastern states during summer and early fall when mosquitoes are present.

Make sure you also consider the horse’s recent travel history, says Pinn-Woodcock. Horses attending shows or other events involving multiple horses from different origins can contract a wide variety of pathogens such as respiratory viruses, she says. Plus, researchers have recently confirmed horses in transit often have slightly weakened immune systems, making them more susceptible to such pathogens.

The travel history of the horse’s stablemates should be considered as well, she adds. Horses that have recently arrived on the premises or have been out traveling and returned home could have brought pathogens with them—without appearing sick themselves. “There’s a lot that goes into these risk analyses,” Pinn-Woodcock says.

The Veterinarian’s Workup on Fever
Workups for fevers of unknown origin start with a detailed history, followed by a thorough clinical exam of each system in affected horses: respiratory, gastrointestinal, musculoskeletal, urogenital, and so on, Felippe says. “You use a multidirectional approach to narrow it down,” she says.

Based on the observations, vets collect diagnostic specimens such as nasal swabs, blood samples, and possibly peritoneal or cerebrospinal fluid for laboratory analyses. They might also analyze the f***s for equine coronavirus or infectious bacteria such as Salmonellaor Clostridium, which cause intestinal disease.

Our sources say that while these samples can be used for specific disease testing based on the case context, complete blood counts (CBCs) and complete serum chemistry profiles can also provide clues. These comprehensive exams can point to trends and even specific organ systems that might be affected, based on values that are within normal range or not. For example, high levels of the enzymes aspartate transaminase (AST) and gamma-glutamyl transferase (GGT) suggest a liver problem, and elevated blood urea nitrogen (BUN) and creatinine point to kidney issues.

“This can be a great place to detect a hint about what’s going on,” Pinn-Woodcock says.

Finally, additional tests might include imaging such as X ray or ultrasound, checking for evidence of inflammation or infection in various internal organs.

Even so, test results themselves don’t necessarily give a definitive answer, says Felippe. Tests might return negative results if the active pathogen shedding and replication period has passed, for example. Positives could represent remnants from previous infection or exposure that aren’t the cause of the current fever, or they could be an inflammatory response to vaccination.

“The veterinarian really has to understand what the results mean and how valid they are,” she says. “Even a positive result needs to be interpreted within the case context.”

On the opposite end of the spectrum, test results might not show anything at all—at least, not initially. “Fevers of unknown origin can sometimes take multiple rounds of testing,” Pinn-Woodcock says. “It’s a process. It can take time for the veterinarian to get to the bottom of it—and patience on everyone’s part. It’s not always straightforward.”

Dedicated Fever-of-Unknown-Origin Test Panels
Within a year of arriving at Cornell’s laboratory, Pinn-Woodcock realized her team was getting lots of calls from equine practitioners seeking help for diagnosing horses with fevers without other clinical signs. “It was confusing for them to figure out what sample types they needed and which tests to request,” she recalls.

So, in 2019 she developed a dedicated fever-of-unknown-origin test panel targeting the most common causes—at least in the northeastern U.S. The panel streamlines the testing process, eliminates confusion, and aids efficiency, leading to faster answers and cheaper costs, she says. The Cornell panel provides results on 10 pathogens within three days. This makes it easier for veterinarians to screen their patients for all these things to help them figure out a treatment plan, Pinn-Woodcock says.

University of California Davis researchers have also developed a fever-of-unknown-origin panel adapted to the western U.S., she adds. Regardless of where veterinarians are, they can ship samples to these labs or use existing panels as models to create their own lists of tests to order from local diagnostic labs.

Still, these dedicated panels don’t cover everything, Pinn-Woodcock adds. They just make it easy to rule out the most common infectious causes. “There are many other causes of fever,” she says.

Recurrent Fevers and Immune Disorders in Horses
Horses affected by fevers that just never seem to go away, or keep coming back after treatment, might have an immune disorder, Felippe says. In her research she’s shown these disorders can be particularly difficult to diagnose due to the immune system’s various cell types and functions, she says. “You could have something that affects one area of the immune system but not the other areas,” she explains. “And we do not have tests for all areas of the immune system, so we can miss the real cause.”

Still, some tests can be “quite revealing,” she adds. Low concentrations of immunoglobulins M and G (IgM and IgG) in a horse’s blood, for example, indicate impaired antibody production. “These horses have a decreased capacity to produce enough antibodies to fight against diseases, making them highly susceptible to various pathogens all the time,” she explains.

The immune system can also overreact, creating exaggerated immune responses, Felippe says. Such immune hypersensitivity leads to frequent fevers and tissue inflammation. “It’s a bit antagonistic,” she says. “The immune system is to use its cells and mediators for protection, while losing control of itself and causing damage.”

Take-Home Message
Fevers flag a health problem, but without other clinical signs it can be tricky to determine what that problem is. Using clues such as season, region, and recent travel history can help narrow down the possibilities, and certain diagnostic labs offer dedicated test panels that can help veterinarians efficiently diagnose—or rule out—the most common causes. Our sources indicate that with hundreds of infectious and noninfectious causes for fevers, identifying the issue often demands time and patience. Diligent, collaborative work among horse owners, vets, and laboratories frequently leads to proper diagnoses and targeted treatment.

The Horse