7 Common Equine Diseases and How To Recognize Them

Horses are remarkably resilient animals, but they’re not immune to illness. Recognizing the early signs of equine disease is key to effective veterinary care. But because horses instinctively mask pain and weakness, it can be difficult to know when something is wrong—even for the most experienced horse owners. 

Use this guide to help determine if your horse is sick, learn the risks and signs of common equine diseases, and know when to isolate an individual horse or group of infected animals to protect the rest of the herd. 

Knowing what’s normal for a healthy horse can help you identify early warning signs before a horse’s condition becomes serious. The outcome of an illness—and its potential impact on the herd—often depends on how soon they receive veterinary attention, whether the condition is neurologic, infectious, or bacterial, and whether the horses are vaccinated. 

Clinical symptoms of common equine diseases may include: 

• Lethargy 

• Fever 

• Lameness 

• Abnormal stance 

• Nasal discharge 

• Changes in appetite or performance 

• Behavior changes (e.g., depression, agitation or new/recently worsened repetitive behaviors)  

Any unexplained change merits a veterinary exam.  

Recognizing the early clinical signs of these common equine diseases can help you protect your healthy horses—especially if unvaccinated horses are present—and seek prompt veterinary care for sick horses.  

Laminitis is one of the most common diseases affecting adult horses. This painful condition causes inflammation and separation of the laminae within the hoof. Common causes include excessive weight-bearing (obesity), high carbohydrate consumption, and endocrine disorders involving insulin regulation. Other cases of laminitis are triggered by systemic inflammation, infection, or bacterial toxins in the bloodstream—often caused by metritis, pleuritis, enteritis, or colitis.  

Laminitis commonly affects the front feet, but any limb can be affected. Clinical disease signs include: 

• Severe pain 

• Extremely stiff or short-strided gait 

• Braced or rocking horse posture (weight shifted to the hind limbs) 

• Strong digital pulses 

• Reluctance to lift the hoof for exam or care 

Treatment focuses on the underlying cause (analgesia, cryotherapy, hoof support, corrective farriery and management of systemic disease). A small number of metabolic drugs (for example, SGLT2 inhibitors such as ertugliflozin) are being investigated for insulin-dysregulated horses with EMS, but these are experimental/off-label and not a substitute for immediate local laminitis care — consult your veterinarian. 

Equine protozoal myeloencephalitis (EPM) is an infectious neurologic disease that affects a horse’s central nervous system (CNS). Affected horses are exposed to EPM through contaminated feed or water infected with Sarcocystis neurona. These protozoal spores enter the horse’s body and attack any or all parts of the CNS. Horses with EPM can display a range of neurologic signs, including: 

• Weakness 

• Loss of coordination (ataxia) 

• Muscle loss 

• Appetite loss 

• Changes in the horse's head or face (tilt, drooping ears, drooling) 

• Seizures 

• Behavior changes 

Progression of equine protozoal myeloencephalitis can be gradual or rapid, leading to varying degrees of neurologic dysfunction and occasionally death. Antiprotozoal medications such as ponazuril can help in some cases, but relapse is possible. 

Gastric ulcers are a common equine health problem. EGUS refers mainly to ulceration of the equine stomach (both squamous and glandular regions); foals may also develop severe ulceration that involves the pylorus or proximal small intestine. Frequently associated with stress and certain feeding regimens, ulcers are most common in performance horses and young foals—although any horse can be affected. 

Signs of EGUS include: 

• Reduced performance 

• Abdominal pain (colic) 

• Lethargy 

• Reduced appetite 

• Poor appearance  

Additional signs in foals may include: 

• Severe diarrhea 

• Poor nursing 

• Frothing or drooling  

By the time a foal shows visible signs, ulcerations are severe and require veterinary attention.  

Gastrointestinal protectant and acid-reducing products like sucralfate or omeprazole may benefit EGUS-prone horses and heal the affected gastric lining. Treatment options may involve alleviating stress, anti-inflammatory medications, diet modification, and supportive care. 

Equine Cushing’s disease, or pituitary pars intermedia dysfunction (PPID), is a degenerative endocrine equine disorder that affects older horses. PPID results from dysfunction of the pars intermedia of the pituitary and abnormal production of POMC-derived peptides/ACTH; this leads to progressive signs (hirsutism, abnormal fat distribution, laminitis risk). Pergolide is the established medical therapy; veterinarians should follow approved dosing and monitoring guidelines. 

Although PPID can be managed with supportive care, it is a progressive condition. In the early stages, affected horses can experience various signs, including: 

• Coat changes, such as a curly coat 

• Inability to shed or patchy hair loss 

• Weight or muscle loss 

• Unusual fat accumulations 

• Increased thirst and urination 

• Frequent infections (including respiratory infections) 

• Lethargy 

• Laminitis  

• Insulin resistance 

Persistently high cortisol levels can lead to permanent damage and affect the horse’s quality of life. Early recognition, guidance by an equine veterinarian, and proper management of PPID, which often includes pergolide administration, are essential to supporting affected horses. 

Infectious equine conditions are highly contagious diseases that can be shared through contaminated equipment, direct contact, or the air. Equine influenza, strangles, and equine herpesvirus (EHV) can move rapidly through large horse populations—especially those that include young or unvaccinated horses. Some equine infectious diseases (for example EIA, certain forms of EHV-1, equine influenza, strangles) are reportable to animal health authorities; reporting requirements vary by region — contact your state veterinarian or check USDA/APHIS guidance. 

Signs include: 

• High fever 

• Coughing 

• Nasal discharge and other upper respiratory tract signs 

• Lethargy 

• Swollen lymph nodes  

In some cases, equine herpes virus can progress to a neurologic form and may cause abortion or complications in pregnant mares. 

Other infections can be transmitted by biting insects, such as tick-borne Lyme disease or mosquito-borne West Nile Virus (WNV). Insect repellents may help decrease exposure to blood-sucking insects in the environment, while WNV vaccination can protect against disease development.  

Treatment depends on the cause — antibiotics (eg, doxycycline, where indicated) for bacterial infections, antivirals/supportive care for viral disease, and symptomatic/supportive therapy (fluids, anti-inflammatories) as needed. 

Navicular syndrome is a collection of conditions that affect an area of the hoof known as the navicular or podotrochlear apparatus. This area includes the navicular bone as well as surrounding ligaments and tendons. Navicular syndrome is painful and often affects both front hooves. It is typically caused by increased forces on the hoof, such as excess weight, poor trimming or shoeing, hard surfaces, or structural abnormalities.  

Horses with navicular syndrome may show signs such as: 

• Lameness 

• Reduced performance 

• Stiff movement 

• Shortened stride 

• Pain and sensitivity 

Early identification and management of navicular syndrome, such as corrective shoeing, anti-inflammatories such as phenylbutazone, and medications such as isoxsuprine, can help improve comfort and function. The outcomes of these treatments vary; discuss with your farrier and veterinarian. Please note that phenylbutazone has a narrow therapeutic index and withdrawal/competition rules apply — use under veterinary guidance. 

As shown by many of these conditions, lameness is a common sign of many equine diseases and illnesses. It is usually caused by an inflammatory process such as arthritis, joint disease, or bacterial or viral diseases like tick-borne Lyme disease or mosquito-borne West Nile Virus.  

Because lameness can indicate numerous conditions, thorough evaluation by an equine veterinarian is key to effective pain relief and return to function. Routinely observing your horse’s movement and behavior can help you recognize lameness and pain before it becomes severe, while consistent veterinary care, proper nutrition, and vaccinations can help prevent many common causes. 

While waiting for the equine veterinarian, isolate sick horses from the herd to minimize exposure and disease spread. Until you know the cause of the illness and whether it is infectious, practice good hygiene and husbandry. This includes: 

• An isolation period for new horses 

• Stripping and cleaning stalls where affected animals were housed 

• Maintaining separate grooming equipment, medical instruments, and feeding pans 

• Using hand sanitizer between interactions 

It's also helpful to practice this protocol when bringing in a new horse. This gives time for any hidden infections to show up during the incubation period, before they can spread. 

Whether you’re caring for a horse with a chronic condition or managing a sudden and unexpected ailment, convenient access to high-quality equine medications and guidance makes all the difference. Wedgewood provides an extensive catalog of equine preparations, a dedicated team of specialists, and convenient home delivery—right to your barn or home—to help you keep your horse healthy.