Tryon Equine Hospital P.L.L.C




How do I know if my horse has Equine protozoal myeloencephalitis (EPM)?


How do I know if my horse has Equine protozoal myeloencephalitis (EPM)?

Equine Protozoal myeloencephalitis (EPM) is a commonly diagnosed neurological disease of horses. It is caused by Sarcocystis neurona, a protozoal parasite commonly shed in the feces of opossums, which is ingested by horses when grazing, eating contaminated food or drinking water.

The first step in determining if your horse has EPM is having a through neurological exam performed. This entails examining the horse’s full nervous system, for example the brain, brain stem, and spinal cord. EPM can affect all of these parts of the nervous system, but more commonly has a predilection for the spinal cord.

The gait examination is essential for assessing the spinal cord.  This requires looking at the horse in a straight line, but also while performing different maneuvers, such as walking up and down a small slope, walking with the head elevated, walking in serpentines, and walking in tight circles. The gait exam is most important, in determining whether the horse has proprioceptive deficits or ataxia (i.e. meaning the horse does not known where he is putting his feet in relationship to space). Ataxia can be subtle to clearly evident. Your veterinarian will grade the severity of the ataxia based on the neurologic exam. Ataxic horses can have impaired performance and can represent a risk to the rider and horse.  If the horse is determined to have neurologic deficits involving his gait, then further diagnostics are required and will most likely include testing for EPM, since the disease is very prevalent in this area of the country.

However…..Testing the horse’s blood does not provide a definite diagnosis that the horse has EPM; it only tells you the horse has been exposed to Sarcocystis neurona (the protozoal parasite responsible for EPM). The blood test shows you the horse has produced antibodies in response to exposure to the parasite. This does not equal central nervous system disease. Indeed, to prove that the parasite is responsible for clinical signs of disease affecting the nervous system, showing that production of antibodies within the central nervous has occurred and evaluating it with the blood concomitantly is much more reliable. This is done by obtaining spinal fluid from your horse, through a procedure known as a cerebral spinal fluid (CSF) tap, which is often conducted by a board-certified internist.

Dr. Emilie Setlakwe is our board-certified internist with significant experience dealing with neurological diseases. She had the privilege of being trained by one of the very few double boarded internal medicine/neurology large animal specialists. Dr. Setlakwe is more than happy to perform neurological evaluations and perform a cerebrospinal fluid tap if required.

Call our office at (828) 894-6065 to make an appointment with Dr. Setlakwe to see your horse. If you have a specific question, you can email her at