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Intestinal Entamoeba histolytica amebiasis

Karin Leder, MBBS, FRACP, PhD, MPH, DTMH
Peter F Weller, MD, MACP
Section Editor
Edward T Ryan, MD, DTMH
Deputy Editor
Elinor L Baron, MD, DTMH


Intestinal amebiasis is caused by the protozoan Entamoeba histolytica. Most infection is asymptomatic; clinical manifestations include amebic dysentery and extraintestinal disease [1]. Worldwide, approximately 50 million people develop colitis or extraintestinal disease, with over 100,000 deaths annually [2]. Extraintestinal manifestations include amebic liver abscess and other more rare manifestations such as pulmonary, cardiac, or brain involvement; these are discussed separately. (See "Extraintestinal Entamoeba histolytica amebiasis".)

There are four species of intestinal amebae with identical morphologic characteristics: E. histolytica, E. dispar, E. moshkovskii, and E. bangladeshi [3,4]. Most symptomatic disease is caused by E. histolytica; E. dispar is generally considered nonpathogenic. Reported infections with E. moshkovskii are becoming more frequent, with increasing evidence of its potential pathogenicity emerging [5]. The pathogenic potential of E. bangladeshi remains unclear [5,6].

Issues related to intestinal E. histolytica infection will be reviewed here; issues related to extraintestinal E. histolytica infection are discussed separately. (See "Extraintestinal Entamoeba histolytica amebiasis".)


Amebiasis occurs worldwide; the prevalence is disproportionately increased in developing countries because of poor socioeconomic conditions and sanitation levels. Infection with E. dispar occurs approximately 10 times more frequently than infection with E. histolytica [3]. Areas with high rates of amebic infection include India, Africa, Mexico, and parts of Central and South America. The overall prevalence of amebic infection may be as high as 50 percent in some areas [3].

In developed countries, amebiasis is generally seen in migrants from and travelers to endemic areas. E. histolytica is not a common cause of travelers' diarrhea, and gastrointestinal infection is uncommon in travelers who have spent less than one month in endemic areas. In one prospective study of German travelers to the tropics, only 0.3 percent had pathogenic E. histolytica infection [7]. Institutionalized patients and sexually active homosexuals are also at increased risk of infection [8].

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Literature review current through: Nov 2017. | This topic last updated: Nov 06, 2017.
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