DEFINITION Amoebiasis is an infection of the large intestine produced by Entamoeba histolytica. There are 7 species of amoeba that naturally parasitize the human mouth and intestine, but of these only E. histolytica causes disease. The organism may behave as a parasite (by harming the host) or as a commensal (when it does no harm to the host). EPIDEMIOLOGY Worldwide distribution