Sarcocystis Neurona

Sarcocystis neurona is a member of the coccidia, a group of single-celled parasites of medical and veterinary importance including Eimeria, Sarcocystis, Neospora, and Toxoplasma. Unlike Eimeria, a single-host enteric pathogen, Sarcocystis, Neospora, and Toxoplasma are two-host parasites that infect and produce infectious tissue cysts in a wide range of intermediate hosts.

The protozoan Sarcocystis neurona is most commonly associated with equine protozoal myeloencephalitis (EPM), a serious disease of horses, and its management continues to be a challenge for veterinarians. Sarcocystis neurona has also emerged as a common cause of mortality in marine mammals, especially sea otters (Enhydra lutris). EPM-like illness has also been recorded in several other mammals, including domestic dogs and cats.

Sarcocystis neurona has a wide host range relative to other species in the genus Sarcocystis. The North American opossum (Didelphis virginiana) and the South American opossum (D. albiventris) are its known definitive hosts. Several other animal species are its intermediate hosts. In some hosts, only schizonts have been identified and these are considered aberrant hosts. Mature sarcocysts are essential for the completion of the life cycle. Hosts in which mature sarcocysts have been demonstrated are the intermediate hosts. Laboratory-raised opossums excreted sporocysts after feeding naturally infected skunk, raccoon, sea otter or armadillo muscle, indicating that they are proven intermediate hosts of Sarcocystis neurona.

While Toxoplasma form cysts in any organ, Sarcocystis cysts are largely restricted to muscle.

In humans, Sarcocystis neurona is associated with acute sarcocystosis. Sarcocystosis is typically asymptomatic but can be associated with muscle inflammation, diarrhea, or infection of the central nervous system.


  1. An update on Sarcocystis neurona infections in animals and Equine Protozoal Myeloencephalitis (EPM). J. P. Dubey,a,* D. K. Howe,b M. Furr,c W. J. Saville,d A.E. Marsh,d S. M. Reed,e and M. E. Griggf Vet Parasitol. Author manuscript; available in PMC 2016 Apr 15.
  2. Systems-Based Analysis of the Sarcocystis neurona Genome Identifies Pathways That Contribute to a Heteroxenous Life Cycle. Tomasz Blazejewski et al. mBio. 2015 Jan-Feb; 6(1): e02445-14.



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