Q. My horse was diagnosed about six months ago with EPM (equine protozoal myeloencephalitis). He is a 5-year-old gelding. This affected his hindquarters, and he is still stiff and sometimes wobbly. Is there anything I can do to help him gain his strength back?

Sharon Todd, Georgia

A. EPM is caused by a parasite that infects the central nervous system (brain and spinal cord) of the horse. Clinical signs associated with EPM can be quite variable, depending on exactly where in the brain or spinal cord the parasite is living.

There are at least three possible reasons why your horse might be stiff and wobbly. A stiff, wobbly gait is common in horses with EPM; however, it is also common with many other diseases. One possibility is that your horse's problems are not the result of EPM. Was the diagnosis made only on the basis of clinical signs, or did you have a blood or spinal fluid test? Even the blood and spinal fluid Western blot tests can result in "false positives," meaning that even though the test is positive, EPM is not the cause of the horse's problem.

Another possibility is that any treatment you administered might have been ineffective at completely eliminating the parasite. Some horses require multiple rounds of treatment.

A third possible reason for your horse's continuing stiffness and incoordination is that, even though the parasite is now gone, the damage to the nervous system caused by the parasites remains. Many horses with EPM are never 100% normal again after treatment. However, some of these horses will benefit from a controlled, carefully prescribed regimen of physical therapy.

I suggest you contact your veterinarian and discuss the three possible reasons for your horse's continuing problems. The resultant plan might include another evaluation by your veterinarian, referral to a specialist for a second opinion, additional treatment for EPM, or developing a specific physical therapy plan.

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