Equine protozoal myeloencephalitis (EPM) is a neurologic disease of horses caused by protozoal infection of the central nervous system. Sarcocystis neurona causes most cases; Neospora hughesi can also cause disease. Both organisms are obligate intracellular pathogens in the protozoan phylum Apicomplexa.

Clinical signs are variable and can mimic most other neurologic diseases as well as musculoskeletal problems. While EPM can mimic many diseases, certain clinical signs increase or decrease suspicion for EPM. Multifocal neurologic signs with asymmetric deficits (including ataxia) or muscle atrophy should increase clinical suspicion, while fever or evidence of pain accompanying the neurologic signs should decrease clinical suspicion.

Resource Type

  • Guideline


  • Equine protozoal myeloencephalitis (EPM)

Publish Date

February 19, 2021