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Infection can cause self-limited watery diarrhea, cramps, and low-grade fever in immunocompetent people. In people with AIDS and CD4 counts below 200, diarrhea may be chronic and profuse, with malabsorption, weight loss, or biliary disease. Diagnosis relies on finding oocysts in stool with modified acid-fast staining; multiple stool samples or duodenal biopsy may be needed. TMP-SMX is first-line therapy, while alternative regimens may be considered for severe intolerance or allergy. Care also includes rehydration and electrolyte replacement; for patients with AIDS, antiretroviral optimization and appropriate secondary prophylaxis are important. Prevention focuses on safe water, hand hygiene, washing produce, and sewage treatment.