95 - Sarcocystosis

Abstract

•Cause: Protozoan parasites belonging to order Apicomplexa, family Sarcocystidae. There are more than 200 named species of Sarcocystis. Disease in dogs and cats results from infection with Sarcocystis neurona or S. neurona-like organisms, Sarcocystis felis, Sarcocystis canis, and Sarcocystis caninum.•First Described: The encysted stage of the parasite (sarcocyst: in Greek, sarkos = flesh, kystis = bladder) was first found in the muscle of a house mouse in 1843, but its life cycle remained unknown until 1970. Natural sarcocyst infection in dogs was reported in 1966 and in cats in 1986.•Affected Hosts: Most warm-blooded animals, humans, and some cold-blooded animals.•Intermediate and Definitive Hosts: These vary with each Sarcocystis species.•Geographic Distribution: Worldwide. Some species may be confined to geographic locations defined by the distribution of definitive or intermediate hosts. For example, S. neurona is confined to the Americas, dependent on the geographic location of its definitive host, the opossum (Didelphis spp.).•Route of Transmission: Definitive hosts become infected by ingestion of muscles of an infected intermediate host. Intermediate hosts are infected by ingestion of food or water that has been contaminated with sporocysts.•Major Clinical Signs: These depend on the Sarcocystis species and the specific intermediate hosts infected, but include fever, lethargy, neurologic signs (S. neurona), muscle pain, weakness (myositis due to sarcocysts), and icterus as a result of hepatitis (S. canis, S. caninum).•Differential Diagnosis: Toxoplasmosis, neosporosis, hepatozoonosis, rabies, CDV infection, infectious canine hepatitis, West Nile virus infection, canine monocytic ehrlichiosis, RMSF, deep mycoses, migrating ascarid infections, neuronal storage diseases, granulomatous or eosinophilic meningoencephalitis, immune-mediated neuromuscular diseases, primary or metastatic neoplasia.•Human Health Significance: Humans can be definitive and intermediate hosts for certain species of Sarcocystis. However, Sarcocystis species of dogs and cats do not infect humans.