Numerous mammals primarily including armadillos, raccoons, sea otters, skunks, and cats serve as intermediate hosts for S. neurona and ingest many sporocysts.

[3] There are many unanswered questions concerning the development of the disease once this protozoan infects the horse by ingestion of sporocysts in contaminated water and feed.

It is presumed that sporocysts release sporozoites that are able to penetrate the intestinal wall and enter arterial endothelial cells within the horse.

When the merozoite accesses the central nervous system, it is suggested that schizonts form in one or more areas of the CNS including the cerebrum, brainstem, cranial nerves, and/or the spinal cord of the horse.

Transmission of the protozoan from the infected horse to other animals is not possible based on the schizonts and daughter merozoites remaining uninfective in the neural tissue.

[5] Recent studies suggest that approximately 22–65% of horses in the United States, depending on the geographic location, are seropositive for S. neurona antibodies.

[5] Sarcocystis neurona can parasitize all regions of the central nervous system, including the anterior cerebrum to the end of the spinal cord.

[6] Early clinical signs of EPM include stumbling and frequent interference, which can often be mistaken for lameness of thoracic and/or pelvic limbs in horses.

[10] However, due to EPM only occurring in a small proportion of horses infected with S. neurona, the detection of antibodies against this parasite offers minimal diagnostic value.

[11] Enzyme-linked immunosorbent assays (ELISAs) are easy to perform, provide a more objective interpretation of the results, and allow for increased throughput testing.

Validative studies have proved that the SnSAG ELISAs are specific and do not cross-react with serum from horses infected with other species of Sarcocystis.

Treatment of horses with suspected equine protozoal myeloencephalitis should begin immediately after clinical signs and symptoms of the disease have been recognized and confirmed.