One of the most common equine neurologic diseases—equine protozoal myeloencephalitis, or EPM—is also one of the most difficult to diagnose. Further, with only three FDA-approved treatment options, treating EPM can be a challenge as well.

At the 2013 Western Veterinary Conference, held Feb. 17-21 in Las Vegas, Nev., Laurie Beard, DVM, MS, Dipl. ACVIM, associate clinical professor at Kansas State University’s College of Veterinary Medicine, reviewed the current diagnostic and treatment options for veterinary attendees.

Beard said that EPM is the most common equine neurologic disease in North America, and it affects horses of all ages, breeds, and disciplines. It is a progressive (increasing in extent and severity) and potentially fatal neurologic disease caused by protozoal (single cell) microorganisms—most commonly Sarcocystis neurona and less commonly Neospora hughesi—that cause inflammation in the brain and/or spinal cord. Clinical signs of disease vary widely, she said, and include:

  • Ataxia (incoordination), ranging from mild to severe, depending on disease status;
  • Muscle atrophy;
  • Lameness, ranging from mild to severe;
  • Head tilting; and
  • In severe cases, recumbency (the inability to stand or rise).

In many cases, EPM clinical signs are asymmetric, meaning one side of the horse’s body is more severely affected than the other.

Beard also noted that disease prevalence generally correlates with opossum (S. neurona‘s definitive host and the animal that passes EPM-causing organisms on to horses) populations i