Equine Protozoal Myeloencephalitis (EPM) is a serious disease, which attacks the horse’s central nervous system and can be difficult to diagnose because its signs often mimic other health problems in the horse which signs ranging from mild to severe. More than 50 percent of all U.S. horses have been exposed to the parasite that causes EPM. Horses can come into contact with the parasite while grazing or eating feed or drinking water contaminated by opossum feces. Fortunately, not all horses exposed to the parasite develop the disease.

The clinical signs of EPM can be quite varied. Clinical signs are usually asymmetrical (not the same on both sides of the horse). Actual signs may depend on the severity and location of the lesions that develop in the brain, brain stem or spinal cord.

If left undiagnosed and untreated, EPM can cause devastating and lasting neurological damage. Use this checklist of symptoms from the American Association of Equine Practitioners (AAEP) when assessing your horse’s condition for the possibility of EPM:

• Ataxia (incoordination), spasticity (stiff, stilted movements), abnormal gait or lameness.
• Incoordination and weakness which worsens when going up or down slopes or when head is elevated.
• Muscle atrophy, most noticeable along the topline or in the large muscles of the hindquarters, but can sometimes involve the muscles of the face or front limbs.
• Paralysis of muscles of the eyes, face or mouth, evident by drooping eyes, ears or lips.
• Difficulty swallowing.
• Seizures or collapse.
• Abnormal sweating.
• Loss of sensation along the face, neck or body.
• Head tilt with poor balance; horse may assume a splay-footed stance or lean against stall walls for support.

Contact your veterinarian immediately if you suspect your horse has developed EPM. The sooner treatment begins, the better the horse’s chances for recovery. For more information on methods of prevention and the treatment options for EPM, ask your equine veterinarian for a copy of the “EPM: Understanding this Debilitating Disease” client education brochure, provided by the AAEP in partnership with Bayer Animal Health, an AAEP Educational Partner. Additional information also can be found on the AAEP’s horse-health Web site.

The American Association of Equine Practitioners, headquartered in Lexington, Ky., was founded in 1954 as a non-profit organization dedicated to the health and welfare of the horse. Currently, AAEP reaches more than 5 million horse owners through its over 9,000 members worldwide and is actively involved in ethics issues, practice management, research and continuing education in the equine veterinary profession and horse industry.

Permission for use is granted with attribution given to the AAEP and Bayer Animal Health.