It is widely disseminated in nature in surface water, mammals, birds and reptiles. Transmission occurs from animals or water to man by the oral route.
Diagnosis depends on demonstrating the acid fast oocysts in stool.
Most common symptom is watery diarrhea with abdominal pain, anorexia and weight loss. Self limited disease in healthy individuals lasting 10-20 days. Severe disease occurs in immunocompromised patients, esp. Incubation period is 2-14 days. Asymptomatic shedding after infection lasts 5 weeks.