A rare infection due to the protozoan parasite Sarcocystis nesbitti. Patients are typically from Southeast Asia (and particularly Malaysia). Humans become infected by eating meat or water contaminated by oocysts from snakes. Patients may be asymptomatic. If there are symptoms, they may include fever, headache, cough, myalgia, or arthralgia.

Diagnosis is made by examining stool (looking for sporocysts or oocysts). Magnetic resonance imaging of affected muscle may show findings consistent with myositis. Muscle biopsy may show the organisms on histopathologic examination. Laboratory studies are not specific, but eosinophilia may be present.

There are no conclusive recommendations for treatment, and in most cases symptoms improve without therapy.