Humans can serve as either the definitive or intermediate host to the protozoan parasite, Sarcocystis. When humans are the definitive host, they have an intestinal infection, which is usually characterized by self-limited watery diarrhea. When humans are the intermediate host, the parasite develops tissue cysts throughout the body and the patient presents with eosinophilia and myalgias. Shown here is a tissue cyst (sarcocyst) within skeletal muscle. Each sarcocyst contains multiple bradyozoites.