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Amebiasis

Amebiasis

In the United States, returning travelers and recent immigrants from developing countries account for the vast majority of amebiasis cases.

What is amebiasis?

As the name suggests, amebiasis is a disease caused by an amoeba. In this case, the culprit is Entamoeba histolytica, a one-celled, protozoan parasite that often lurks in food and water contaminated with human feces.

In approximately 90 percent of all cases, E. histolytica doesn’t cause any problems. But if conditions are right, the parasite can start eating away at the walls of your intestine, causing illness. In rare cases, it can spread to other organs, like the liver. Complications occur more commonly in young children, pregnant women, the elderly, and anyone with a compromised immune system.

While this parasite is rare in the United States and other developed countries, it thrives throughout much of Asia, Africa, Central America, Mexico, and South America — anywhere where poor sanitary conditions are the norm. Generally, infection rates in travelers vary depending on the destination, the local hygiene practices, and the length of time people are exposed to local germs. According to the Centers for Disease Control and Prevention, amebiasis causes approximately 50 million serious illnesses and up to 100,000 deaths worldwide every year.

Who is at risk for amebiasis?

In the United States, returning travelers and recent immigrants from developing countries account for the vast majority of amebiasis cases. Outbreaks have also occurred in mental hospitals with poor sanitary conditions. In a few cases, the disease has been transmitted through unprotected anal sex.

What are the symptoms of amebiasis?

Most people infected with E. histolytica are symptom-free, and any symptoms that do arise, like diarrhea, abdominal pain, and minor cramping, are usually mild. The disease may exist without symptoms for many years. In some people, however, the disease gradually develops more severe symptoms. Eventually, you may have profuse, bloody diarrhea along with a fever, intense abdominal pain, and rapid weight loss. Such extreme cases are also called amebic dysentery. If the infection spreads to your liver, which is rare, you may develop a fever, pain in your upper-right abdomen, nausea, vomiting, loss of appetite, weight loss, and fatigue.

How is amebiasis diagnosed?

Detecting a case of amebiasis used to be very difficult. Fortunately, researchers have developed several tests that can detect E. histolytica in fresh stool samples. The tests aren’t 100 percent accurate, though, and they can’t always make the distinction between E. histolytica and a similar, harmless amoeba that’s 10 times more common.

How is amebiasis treated?

Even if your infection isn’t causing symptoms, your doctor may still recommend treatment to prevent spreading the disease to others. If you don’t have symptoms, your doctor will probably prescribe a single antibiotic. Depending on which antibiotic your doctor prescribes, you may need to stay on the pills for seven to 20 days.

If the infection is enough to make you sick, one drug won’t be enough. Your doctor will probably recommend that you take the common drug metronidazole (Flagyl) for five to 10 days or tinidazole (Tindamax) for three days, followed by a course of antibiotics.

If you have the infection, you can protect others around you by washing your hands regularly with soap and water, especially after using the toilet, after changing diapers, and before preparing food.

How can I prevent amebiasis?

If you’re traveling to an area with poor sanitation, taking a few precautions can protect you from amebiasis and other diseases.

The most important tip: Don’t drink the water. Simply brushing your teeth with tap water, or tossing a couple of ice cubes into your drink can be enough to make you sick. In many areas, the only safe beverages are boiled water, canned or bottled sodas, tea and coffee (made with boiled water), beer, or wine. If it’s not possible to boil your water for at least one minute, treat it with chemical disinfectants such as iodine or chlorine. For extra protection, strain the water through an “absolute 1 micron” filter (available at outdoor supply stores) before adding the disinfectant.

In areas with poor sanitation, the food can be as dangerous as the water. You should be especially suspicious of salads, uncooked fruits and vegetables, unpasteurized milk, raw meat, shellfish, and any foods sold by streetside vendors. In general, fruits that you peel yourself and hot meals are safer choices.

References

Mayo Clinic. New test announcement: Entamoeba histolytica Antigen, Feces.

Centers for Disease Control and Prevention. Diagnostic procedures for stool specimens.

Kucik CJ et al. Common Intestinal Parasites. American Family Physician.

Centers for Disease Control and Prevention. Amebiasis fact sheet.

Petri WA and U Singh. Diagnosis and management of amebiasis. Clinical Infectious Diseases. Vol. 29: 1117-1125.

Treatment options for the eradication of intestinal protozoa. Nature Clinical Practice Gastroenterology and Hepatology.

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