Sarcocystis

This apicomplexan parasite's life cycle is heteroxenous, meaning that it has more than one obligatory host in its life cycle. Sarcocystis relies on the predator-prey relationship of animals. Oocysts are passed through the feces of an infected individual where it undergoes sporogony and becomes infected itself. The oocysts then undergo lysis where the sporocysts are left out in the environment. An intermediate host such as a cow or pig will ingest a sporocyst. Sporozoites are then released in the body and migrate to the muscle tissue where it undergoes asexual reproduction. Once the intermediate host is eaten by the definitive host such as a dog or human, the parasite undergoes sexual reproduction to create macrogamonts and a mircogamonts. They create a zygote which develops into an oocyst, which is passed through the feces completing the life cycle.

Human infection is rare but can happen when undercooked meat is ingested. Symptoms include diarrhea, which may be mild and transient or severe and life threatening. Human outbreaks have occurred in Europe.