From Equine Disease Quarterly, Funded by Underwriters at Lloyd’s, London, Brokers, and Their Kentucky Agents, https://www.uky.edu/Agriculture/VetScience/q_jan02/q-jan02.htm.

Equine Protozoal Myeloencephalitis (EPM) is an infectious, degenerative protozoal disease of the central nervous system of the horse. The causative agent of EPM has been identified as Sarcocystis neurona.  Dr. David Granstrom developed the first pre-mortem test for the presence of S. neurona antibodies in 1993, using a western blot immunoassay. This test is currently the most reliable test that can be performed on serum and cerebrospinal fluid to detect the presence of antibodies to S. neurona.

The incidence of S. neurona is highest in the eastern U.S. because of the geographic habitat of the opossum, which is the definitive host. When ingested in high enough levels, the parasite can cause a broad range of clinical signs, including weight loss, muscle atrophy of the rear limbs, incoordination, urinary and fecal incontinence, gait abnormalities, paralysis, seizures and death.

The purpose of this research was to establish a base-line antibody level for the Morehead State University equine herd in Morehead, Kentucky. The study involved 39 adult horses (stallions, mares, and geldings) of various breeds, ranging in age from 4 years to 33 years of age. All horses were housed at the Derrickson Agricultural Complex on the Morehead State Farm and were housed and fed in a similar fashion