infectious diseases
Amebiasis
Introduction
Amebiasis is infection withEntamoeba histolytica. It is acquired by fecal-oral transmission. Infection is commonly asymptomatic, but symptoms ranging from mild diarrhea to severe dysentery may occur. Extraintestinal infections include liver abscesses. Diagnosis is by identifyingE. histolyticain stool specimens and confirmed with immunoassays-detecting antigen in the stool, or by serologic tests if extraintestinal disease is suspected. Treatment for symptomatic disease is withmetronidazoleortinidazolefollowed byparomomycinor another drug active against cysts in the lumen of the colon. (See also Overview of Intestinal Protozoan and Microsporidia Infections .) Four species ofEntamoebaare morphologically indistinguishable, but molecular techniques show that they are different species: E. histolytica(pathogenic) E. dispar(harmless colonizer, more common) E. moshkovskii(less common, uncertain pathogenicity) E. bangladeshi(less common, uncertain pathogenicity) Amebiasis is caused byE. histolyticaand tends to occur in regions with poor socioeconomic conditions and poor sanitation. The parasite is present worldwide, but most infections occur in Central America, western South America, western and southern Africa, and the Indian subcontinent. In countries with sanitary food and water supplies (eg, US), most cases occur among recent immigrants and travelers returning from endemic regions. Worldwide each year, an estimated 50 million people develop amebic colitis or extraintestinal disease, and as many as 100,000 die. 