Equine Protozoal Myeloencephalitis (EPM)

Photo: Horse affected by EPM

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What is EPM?

EPM is a debilitating neurologic disease in horses caused by protozoa. The opossum is the definitive host that fecally sheds infective Sarcocystis neurona. In areas where opossums and horses coexist, ~50% of horses are seropositive for S. neurona. EPM is also caused by Neospora hughesi, and, although the source is uncertain, N. hughesi has been identified in horses from across the United States.

Making the Diagnosis

While it may not seem difficult to visually identify a horse as neurologic, diagnosing EPM can be a detailed process of evaluating the history, physical examination, and neurological examination of the horse. We encourage trained equine veterinarians to follow our detailed steps to perform a neurological examination of a horse. With results of the exam, veterinarians can then utilize our Diagnostic Flow Chart to determine if laboratory testing to confirm EPM is necessary, followed by the best course of action to treat the horse.

Laboratory Testing

EPM diagnostics, based on indirect fluorescent antibody tests (IFATs), have greater sensitivity than the more common but less sensitive, Western Blot test. The UC Davis Veterinary Medical Teaching Hospital offers two distinct IFATs that can be performed on both serum or cerebrospinal fluid (CSF):

Why SarcoFluor™ and NeoFluor™?

SarcoFluor™ and NeoFluor™ provide quantitative indication of EPM infections by providing actual titers and a likelihood ratio of disease correlating to the titer. UC Davis offers the only commercial platform that tests for both S. neurona and N. hughesi antibodies, ensuring more cost effective and complete screening from a single sample. Compared to other test formats, SarcoFluor™ is more sensitive and specific for serum sample screening, decreasing the likelihood of false-positive results and reducing the need to obtain a CSF sample from an already medically-compromised horse.

UC Davis has a rich history and culture of combining rigorous peer-reviewed research with cutting-edge medicine, and is proud to offer these tests to our clients.