Research Efforts Focus on EPM Prevention

Equine protozoal myeloencephalitis (EPM) is an infection of the brain and spinal cord of horses by single-celled parasites known as protozoa. EPM, which is the most commonly diagnosed neurological disorder in horses, can be a permanently

Share
Favorite
Close

No account yet? Register

ADVERTISEMENT

Equine protozoal myeloencephalitis (EPM) is an infection of the brain and spinal cord of horses by single-celled parasites known as protozoa. EPM, which is the most commonly diagnosed neurological disorder in horses, can be a permanently debilitating or fatal disease. The disease is most commonly (probably greater than 95% of cases) caused by the protozoa Sarcocystis neurona; occasionally, another protozoa known as Neospora hughesi also can cause EPM.


EPM is a disease of North, Central, and South America, and it is only observed in horses outside this region among horses that have been exported from the Americas. This infection is acquired by ingestion of the intermediate stages of the S. neurona parasite, which are passed in the feces of opossums and which contaminate feed and forage consumed by the horse. After the parasite is ingested, it is eliminated by the horse’s immune response in most cases.


In a small minority of cases (probably less than 2%), the organism invades the spinal cord or brain of the horse and grows, resulting in the clinical signs recognized as EPM. The organism is carried to the nervous system either directly by the blood stream or within white blood cells that have engulfed the organism. Horses do not appear to be able to transmit the infection directly to other horses.


The clinical signs of EPM in the horse are quite variable and depend upon the anatomic location in the nervous system in which it resides. Chance seems to favor the spinal cord, and the most common clinical signs expressed are stumbling, a weak, weaving gait, and atrophy of muscles. If the brain is affected, which is far less common, the clinical signs might include blindness, inability to chew or swallow, atrophy of muscles of the head (such as the masseter in the cheek that closes the jaw during chewing), head tilt, or seizures

Create a free account with TheHorse.com to view this content.

TheHorse.com is home to thousands of free articles about horse health care. In order to access some of our exclusive free content, you must be signed into TheHorse.com.

Start your free account today!

Already have an account?
and continue reading.

Share

Written by:

Martin Furr, DVM, PhD, Dipl. ACVIM, is the professor and Adelaide C. Riggs chair in Equine Medicine at Virginia Tech’s Marion duPont Scott Equine Medical Center in Leesburg, Virginia. His research interests include equine neurology, immunology, and neonatology. He is a member of the American College of Veterinary Internal Medicine, American Society of Veterinary Perinatology, American Veterinary Medical Association, and Equine Protozoal Myeloencephalitis Society.

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from TheHorse.com

Sponsored Content

Weekly Poll

sponsored by:

Where do you primarily feed your horse?
328 votes · 328 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with TheHorse.com!