Amebiasis is an infection of the intestines caused by the parasite Entamoeba histolytica.
Entamoeba histolytica can live in the large intestine (colon) without causing disease. However, sometimes, it invades the colon wall, causing colitis, acute dysentery, or long-term (chronic) diarrhea. The infection can also spread through the blood to the liver and, rarely, to the lungs, brain, or other organs.
This condition occurs worldwide, but it is most common in tropical areas with crowded living conditions and poor sanitation. Africa, Mexico, parts of South America, and India have significant health problems associated with this disease.
Entamoeba histolytica is spread through food or water contaminated with stools. This contamination is common when human waste is used as fertilizer. It can also be spread from person to person -- particularly by contact with the mouth or rectal area of an infected person.
Risk factors for severe amebiasis include:
In the United States, amebiasis is most common among those who live in institutions and people who have anal intercourse.
Most people with this infection do not have symptoms. If symptoms occur, they are seen 7 to 10 days after being exposed to the parasite.
Examination of the abdomen may show liver enlargement or tenderness in the abdomen.
Treatment depends on the severity of infection. Usually, metronidazole is given by mouth for 10 days.
If you are vomiting, you may need to receive medications through a vein (intravenously) until you can tolerate them by mouth. Antidiarrheal medications are usually not prescribed because they can make the condition worse.
After treatment, the stool should be rechecked to make sure that the infection has been cleared.
The outcome is usually good with treatment. Usually, the illness lasts about 2 weeks, but it can come back if treatment is not given.
Call your health care provider if you have persistent diarrhea.
When traveling in tropical countries where poor sanitation exists, drink purified or boiled water and do not eat uncooked vegetables or unpeeled fruit. Public health measures include water purification, water chlorination, and sewage treatment programs.
Safer sex measures, such as the use of condoms and dental dams for oral or anal contact, may help prevent infection.
Amebic dysentery; Intestinal amebiasis
Schuster FL, Glaser CA. Amebiasis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 373.
Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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