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Infection follows ingestion of cysts, commonly through contaminated food or water; trophozoites emerge and may invade the colon, causing ulcers and, in some cases, spread to the liver or other sites. Illness ranges from asymptomatic cyst passage to dysentery, severe colitis, and liver abscess. Diagnosis may involve stool testing, antigen detection or PCR, serology, and imaging when abscess is suspected. Treatment depends on the clinical presentation: invasive intestinal disease and liver abscess require a tissue-active agent, followed by a luminal agent to clear cysts. Asymptomatic cyst passers receive a luminal agent. The lesson also addresses drug cautions, pregnancy, resistance, complications, and public-health measures.