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 diarrhea. The infection can also spread through the blood to the liver and, rarely, to the lungs, brain or other organs.

This condition can be seen anywhere in the world, 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.

The bacteria is spread through food or water contaminated with stools. This 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.

Intestinal amebiasis causes frequent diarrhea, often with abdominal pain. Rectal pain during the diarrhea (tenesmus) is also common. The diarrhea may contain blood or mucus. Usually, the illness lasts about 2 weeks, but it can come back again and again if not treatment is given.

Risk factors for severe amebiasis include malnutrition, old age, pregnancy, use of steroids, malignancy (cancer), and alcoholism. Recent travel to a tropical region is also a risk factor.

In the United States, amebiasis is most common among those who live in institutions and people who have anal intercourse. There are an estimated 50 million cases worldwide of amebiasis with 40,000 to 50,000 deaths annually.