Amebiasis is an infection of the intestine (bowel) caused by the parasite Entamoeba histolytica .

Alternative Names

Amebic dysentery; Intestinal amebiasis

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 chronic diarrhea . The infection can also spread through the blood to the liver and rarely, to the lungs, brain or other organs. This condition can occur anywhere in the world, 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. Transmission occurs through ingestion of cysts in fecally contaminated food or water, which is common where human excrement is used as fertilizer. It can also be spread person-to-person -- particularly via oral/anal contact. Cockroaches and house flies can also spread 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 E. histolytica into the wall of the colon may occur in 8-10% of cases and to the liver in approximately 1%. Malnutrition, old age, pregnancy, use of steroids, malignancy (cancer), and alcoholism predispose a person to more severe disease, as does immunosuppression . Recent travel to a tropical region is a risk factor. In the US, amebiasis is most common among gay men and residents of institutions.

Signs and tests

Examination of the abdomen may show liver enlargement and abdominal tenderness. Tests include:

Stool culture

of 3 stool specimens several days apart

Serology

for amebiasis

Sigmoidoscopy

Treatment

Oral antiparasitic medication is the standard treatment for amebiasis. The choice of drug depends on the severity of the infection.

When nausea or vomiting are present, intravenous therapy may be necessary until medications can be tolerated by mouth. Antidiarrheal medications are usually not prescribed and can make the condition worse. After treatment, the stool should be rechecked to ensure that the infection has been cleared.

Expectations (prognosis)

The outcome is likely to be good with treatment.

Complications

Liver abscess

Medication side effects, including

nausea

Spread of the parasite through the blood to the liver, lungs, brain, or other organs

Calling your health care provider

Call your health care provider if persistent diarrhea occurs.

Prevention

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/anal contact, may help prevent infection.