Equine protozoal myeloencephalitis is a heartbreaking disease.

Equine protozoal myeloencephalitis is a neurological disease caused by a tiny parasite. Opossums carry the parasite, and horses contract the disease by eating feed or drinking water contaminated by opossum feces.

EPM is characterized by the three A’s: Asymmetrical ataxia (incoordination) with or without muscle atrophy (degeneration).

Signs of EPM

    • Incoordination (ataxia): stiff, stilted movements (spasticity); abnormal gait or lameness.
    • Incoordination and weakness that worsens when going up or down slopes or when the head is elevated.
    • Muscle atrophy, most noticeable along the topline or in the large muscles of the hindquarters, but sometimes involving the muscles of the face or front limbs.

Since approximately 50 percent of U.S. horses have been exposed to the organism responsible for EPM, it is extremely important to know the signs of infection. Early detection and treatment are key to recovery. Download The Racing Journal's FREE EPM report to start protecting your horse.

    • Paralysis of muscles of the eyes, face or front limbs.
    • 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.

Preventing EPM

    • Keep feed rooms and feed containers closed and sealed.
    • Use feeders that minimize spillage and are difficult for wild animals to get into.
    • Clean up any dropped grain immediately to discourage birds and other scavengers.
    • Feed heat-treated cereal grains and extruded feeds.
    • Keep water tanks clean and filled with clean, fresh water.
    • Maximize your horse’s health and fitness through proper nutrition, regular exercise and routine deworming and immunizations.
    • Schedule regular appointments with your equine veterinarian.

To reduce your horse's risk of contracting this disease, you must take preventative measures. Download The Racing Journal's FREE EPM report for more important tips to prevent exposure to the organism that causes equine protozoal myeloencephalitis.

Treating EPM

In July 2001, the U.S. Food and Drug Administration approved Marquis, an oral paste that was the first medication developed specifically for the treatment of EPM in the United States. Marquis is manufactured by AQHA Corporate Partner Bayer Animal Health and is an FDA-approved EPM treatment.

Marquis is given to a horse once a day for 28 days. Although most horses respond favorably, drug treatment is not a guarantee for 100 percent improvement. The parasite behind EPM causes damage to the brain and/or spinal cord, so even though it may be out of the horse’s body, some of the damage done may be permanent.

It’s also possible that horses can experience relapses of the disease and even be reinfected. Unless the horse’s environment is drastically changed, there will be continued exposure to the parasite. The sooner you treat a horse that’s showing signs of EPM, the better the chances of a positive outcome.