Pregnant mares may abort, riding horses may become unsafe to ride, and breeding stallions may be unable to serve mares. Diagnosis is determined by a veterinarian when there are clear neurological symptoms consistent with EPM as well as a positive blood or cerebrospinal fluid sample. Over 50 percent of the horses admitted to the University of Illinois Large Animal Clinic have tested positive to the presence of antibodies in the blood. Testing cerebrospinal fluid is more accurate, but researchers find it nearly impossible to obtain a blood-free cerebrospinal fluid sample. Even a few red blood cells will contaminate the sample and could result in a false-positive test.
Treatment demands a strong commitment on the part of the owner in both time and finances.
These horses must receive medication twice daily at specific times, often for 4 to 6 months. Veterinary services and lab fees will vary somewhat depending on the individual case, plus what other treatment is needed to stabilize the horse. Owners should discuss these issues with their veterinarian before beginning treatment. If a response is noted within the first 7 to 10 days of treatment, chances for recovery are good. Horses with rapidly worsening symptoms and pregnant mares late in their pregnancy have a less favorable outlook.