Definition of Amebiasis:

Amebiasis is an infection of the intestines caused by the parasite Entamoeba histolytica.

Causes, incidence, and risk factors:

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:

• Alcoholism
• Cancer
• Malnutrition
• Older or younger age
• Pregnancy
• Recent travel to a tropical region
• Use of corticosteroid medication to suppress the immune system

In the United States, amebiasis is most common among those who live in institutions and people who have anal intercourse.