Gastrointestinal Amebiasis

What Is It?

Gastrointestinal amebiasis is an infection of the large intestine caused by microscopic one-celled parasites commonly known as amoebas. Their scientific name is Entamoeba histolytica. Because these parasites live in the large intestine, they are carried in the feces of infected persons, and they can contaminate drinking-water supplies in places where sanitation is poor. They also can contaminate fruits and vegetables grown in areas where human feces are used as fertilizer, or can be transferred on the dirty hands of infected people who have poor hygiene.

Once amoebas enter the mouth, they travel through the digestive system and settle in the large intestine. The harmless strains of the parasite (Entamoeba dispar) live there without causing damage. E. histolytica also can live in the intestine without causing symptoms, but this parasite can cause severe disease. These amoebas may invade the wall of the intestine, causing amoebic dysentery, an illness characterized by intestinal ulcers, bleeding, increased mucus production and diarrhea. These amoebas also may pass into the bloodstream and travel to the liver or, infrequently, the brain, where they form abscesses (pockets of infection).

About 10 percent of the world's population is infected with amoebas, particularly people who live in Mexico, India, Central America, South America, Africa and the tropical portions of Asia. In industrialized countries, amebiasis is most common in recent immigrants and travelers who visit countries where amoebas are prevalent. Cases also have been reported in homosexual men, prisoners and residents of other institutions.

Symptoms

In more than 90 percent of cases, the infecting strain of amoeba does not cause any symptoms. When symptoms occur, they usually begin within months after amoebas first enter the body. In some people, symptoms are mild, consisting of mild pain and gurgling sounds in the lower abdomen, with two or three loose stools daily. In other people, however, there can be full-blown symptoms of amoebic dysentery, including high fever, severe abdominal pain and 10 or more episodes of diarrhea daily. Typically, this diarrhea is watery or contains blood and mucus.

When amoebas spread to the liver and cause liver abscess, symptoms can include fever, nausea, vomiting, pain in the upper right portion of the abdomen, weight loss and an Enlarged liver. It is possible for a person to develop symptoms of an amoebic liver abscess without ever having had the diarrhea associated with amoebic infection of the intestines.

Enlarged liver Definition Hepatomegaly is the enlargement of the liver beyond its normal size. Hepatosplenomegaly is enlargement of both the liver and the spleen - see .