Dr. Gray,

If a horse is treated for a mild case of EPM, and the treatment is "successful", can the horse make a full recovery or will it always be in their systems to where a possible reoccurrence could happen in the future. Thank you, MLS

Dear M.L.S.,

Equine Protozoal Myeloencephalitis (EPM) is a disease near and dear to my heart, as not one but BOTH my horses developed it. My thoroughbred was treated, made a near 100% recovery, and hasn’t had a single relapse. My quarter horse was treated, did not quite recover his ability to canter, and has relapsed so many times I’ve lost count.

According to Dr. Stephen Reed from The Ohio State University College of Veterinary Medicine, the prognosis for horses with EPM seems to be similar regardless of the treatment used: 60 – 75% of horses improve on standard therapy. Unfortunately, less than 25% of affected horses return to their original function. Standard therapy includes:

Pyrimethamine and a sulfonamide
Ponazuril (commonly known as Marquis)
Nitazoxanide (commonly known as Navigator)

The growing concern, however, is the percentage of horses that relapse days, weeks or even months after treatment. Exactly why horses relapse is unclear, but there are three possible reasons: 1) the parasite that causes the disease, Sarcocystis neurona, came out of a form of hibernation within the horse’s body, 2) a small but persistent focus of infection was never completely killed off, or 3) the horse was re-exposed to the parasite.

To ensure your horse’s chances for success, I recommend a three-pronged approach. First, in addition to the standard therapy listed above, work with your veterinarian to determine if anti-inflammatories such as phenylbutazone (“bute”) or flunixin meglumine (“Banamine”) should be used, if an antioxidant such as Vitamin E might support nervous tissue, and if the B-vitamin folic acid may prevent the deficiency sometimes created with treatment.

Second, continue treatment for as long as your veterinarian advises or until tests on CSF (cerebrospinal fluid) come back negative. Third, follow the currently recommended suggestions for preventing EPM in your horse. There are a number of universities currently studying this disease, including:

University of Kentucky College of Agriculture Department of Veterinary Science Gluck Equine Research Center www.ca.uky.edu/gluck

The Ohio State University College of Veterinary Medicine http://vet.osu.edu/462.htm

The University of California—Davis www.vetmed.ucdavis.edu/ceh

Virginia-Maryland Regional College of Veterinary Medicine www.vetmed.vt.edu

Michigan State University College of Veterinary Medicine www.cvm.msu.edu

Another way to keep up with the latest research on EPM or any other animal health issue is to register with the International Veterinary Information Service (IVIS) found at www.ivis.org. This is a not-for-profit organization established to provide information to veterinarians, veterinary students and animal health professionals worldwide using Internet technology. The IVIS website provides free access to original, up-to-date publications organized in electronic books each edited by highly qualified editors, proceedings of veterinary meetings, short courses, continuing education, and more.

Finally, a site that I visit regularly is the online version of The Horse magazine at www.thehorse.com. Like the veterinary research site above you must register, but registration is free and provides you access to over 10,000 articles on horse health. The Horse is an educational partner of the American Association of Equine Practitioners and has an Advisory Board made up of AAEP members.