Amebiasis is a disease caused by a one-celled parasite called Entamoeba histolytica (ent-a-ME-ba his-to-LI-ti-ka). Although anyone can have this disease, it is most common in people who live in developing countries that have poor sanitary conditions. In the United States, amebiasis is most often found in immigrants from developing countries. It also is found in people who have traveled to developing countries and in people who live in institutions that have poor sanitary conditions. Men who have sex with men can become infected and can get sick from the infection, but they often do not have symptoms.