Amebiasis is both an acute and chronic cause of diarrheal disease caused by the protozoa Entamoeba hystolytica. It is transmitted by the faeco-oral route and infection is usually caused by ingestion of cysts from contaminated food and drink. Its manifestations vary from asymptomatic carrier state to severe fulminating illness with mucosal inflammation and ulceration. The diagnosis should also be considered when a patient with bloody diarrhoea fails to show improvement following treatment for shigellosis.

Diagnosis is made by identification of the RBC ingesting trophoizites by direct stool examination.