Amebiasis is a parasitic infection of the gastrointestinal tract. The Parasite responsible is Entamoeba histolytica, a single-cell organism that enters the body when one drinks water or eating food that contains E. histolytica in cyst form.

The cyst is a protective encasing within which the ameba may sustain itself in a dormant stage for weeks to months outside a host (an organism that provides nutrients for a parasite).

Once within the small intestine the cyst ruptures and the ameba emerges to enter its active stage. In this active stage the ameba called a trophozoite, travels to                the large intestine where it feeds on intestinal bacteria.

As the number of trophozoites increases, they burrow into the intestinal mucosa (mucous lining of the colon). Substances trophozoites secrete to digest the substances they consume, cause ulcerations or sores that produce symptoms.

The symptoms of amebiasis, also called amebic dysentery, begin two weeks to four months after ingesting the contaminated food or water. They include abdominal cramping or abdominal pain, frequent bowel movements or diarrhea which may be bloody. Fever is also common especially in children infected with Entameba histolytica.

The diagnostic path includes microscopic examination of stool samples to detect the presence of either cysts or trophozoites.

The doctor may also conduct sigmoidoscopy to examine the colon for the characteristic ulcerations and to rule out other causes of the symptoms.

Occasionally trophozoites penetrate far enough into the intestinal mucosa to enter the blood circulation, which transports them to other organs and extends the infection.
The liver is the most common site for distant infection, where it presents as a hepatic abscess though the lungs and brain may also become involved. In locations other than the colon the trophozoites can cause abscesses, resulting in serious life-threatening illness.

Symptoms of systemic infection depend on the affected area. Amebiasis is most common in countries where community sanitation is poor.

Many people from developed countries suffer episodes of amibiasis attack if exposed to unhygienic conditions. The infection spreads through direct contact with fecal contamination, eating vegetables from contaminated soil or drinking contaminated water.

People who have amebiasis can spread the infection to other people. Diligent hand washing and safe food preparation are effective measures for preventing the spread of amebiasis.

Visitors to countries where sanitation is substandard should follow precautions that include eating only foods that are thoroughly cooked, and drinking only bottled or canned beverages or water boiled for a minimum of one minute.

Treatment for enteric or systemic infection is a combination of antibiotic medications. Appropriate treatment cures the infection. Inadequately treated or untreated amebiasis becomes chronic with cycles of alternating recurrence and remission of symptoms.

Until recently doctors believed it was possible to have an E. histolytica infection without symptoms.

However, although it is possible to have an E. histolytica infection with very mild symptoms, infectious disease specialists has determined a closely related and nearly identical ameba, E. dispar, is the cause of infection when no symptoms are present. E. dispar is benign and does not require treatment.

Ends