Sarcocystis species are single-celled protozoan parasites which cause the disease known as sarcocystosis. Sarcocystis spp. have an intermediate-definitive host life cycle based on a prey-predator relationship. The prey animal (poultry) serve as the intermediate host and the predator (dogs, cats, skunks, and other mammals) is the definitive host.
Poultry become infected when they ingest Sarcocystis oocysts or sporocysts shed in the feces of mammals carrying the organism. Once ingested, Sarcocystis form intramuscular cysts (sarcocysts).