Amebiasis

Alternative names:

amebic dysentery; intestinal amebiasis

Definition:

An infection caused by a tiny parasite (amebae) in the large intestine.

Causes, incidence, and risk factors:

The parasite can live in the large intestine without causing disease; or it can invade the colon wall causing colitis, acute dysentery, or chronic diarrhea. The infection may also spread through the blood to the liver and rarely, to the lungs, brain, or other organs. Amebiasis is present worldwide, but it is most common in tropical areas where crowded living conditions and poor sanitation exist. Africa, Latin America, Southeast Asia, and India have significant health problems associated with this disease. In the United States amebiasis is seen with increased frequency among homosexual males.

Transmission occurs through ingestion of cysts in fecally-contaminated food or water, use of human excrement as fertilizer, and person-to-person contact. Cockroaches and house flies can also spead the cysts. (There are an estimated 50 million cases worldwide of amebiasis with 40,000 to 50,000 deaths annually.)

Typical symptoms of intestinal amebiasis consist of frequent diarrheal bowel movements with cramps or colicky abdominal pain. Pain on defecation (tenesmus) is common. The diarrhea may contain blood or mucus. Uncomplicated attacks may last up to two weeks and recurrences are common unless the diagnosis is made and the individual is treated. Spread of the ameba into the wall of the colon may occur in 8 to 10% of cases and to the liver in approximately 1%.

Malnutrition and alcoholism predispose a person to more severe disease, as does immunosuppression. Recent travel to a tropical region is a risk factor. In the U.S., institutionalized mentally retarded people and male homosexuals are considered high risk groups.