Sarcocystis spp., which include S. bovihominis and S. suihominis, have a very different life cycle, more similar to some helminths than to other protista. They are acquired by eating undercooked or raw beef or pork. The meat contains cysts containing 'bradyzoites' which, when consumed, can lead to intestinal infection in humans. They have an obligatory two host life cycle (see life cycle below). Intermediate hosts acquire the infection by consuming sporocysts from the definitive host species. Extraintestinal infection in humans is rare, as humans are generally the definitive hosts.
Distribution of this parasite is worldwide, but infections are more common where animals are raised for human consumption.
The disease manifests as nausea, diarrhea, abdominal pain, and weight loss; symptoms are most often observed in immunocompromised hosts. The rare person who gets the intramuscular infection (through consumption of sporocysts from feces) may have skeletal and cardiac muscle symptoms.
Diagnosis is sometimes done by noting clinical symptoms together with a history of eating undercooked meat. Sarcocystis spp. can be found in fecal specimens where they appear as single or double sporocysts in or out of an oocyst. The image to the right depicts an oocyst with two sporocysts seen fluorescing under a UV microscope.
Although molecular assays have been developed, they are not yet widely used.
