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Amebiasis is a parasitic infection of the gastrointestinal tract. The parasite responsible is Entamoeba histolytica, a single-cell organism (an ameba) that enters the body by drinking 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 (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 colon (large intestine) where it feeds on intestinal bacteria.
As the population 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 (sores) that produce symptoms.
Symptoms and Diagnostic Path
The symptoms of amebiasis, also called amebic dysentery, begin two weeks to four months after ingesting the contaminated food or water. They include
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 the brain may also become involved.
In locations other than the colon the trophozoites can cause abscesses, resulting in serious or life-threatening illness. Symptoms of systemic infection depend on the affected area.
Treatment Options and Outlook
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 have 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.
Antibiotic Medications to Treat Amebiasis
|ANTIBIOTIC MEDICATIONS TO TREAT AMEBIASIS|
Risk Factors and Preventive Measures
Amebiasis is most common in countries where community sanitation is poor. People who travel in such countries or are immigrants to the United States from such countries, are at highest risk for amebiasis. The infection spreads through direct contact with fecal contamination, such as by 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. Travelers 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 (without ice) or water boiled for a minimum of one minute.
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