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Amebiasis is an infection of the large intestines caused bya single-celled parasite.

What is going on in the body?

The large intestine, or colon, is infected after amebic cysts are eaten. The parasite can then invade the colon, causing it to become inflamed.


What are the causes and risks of the infection?

Direct transmission of amebiasis occurs through contact with infected stool, or contaminated water or soil. The infection can also be transmitted sexually, particularly among male homosexuals.
Fruits and vegetables can be contaminated when they are grown in soil fertilized by human stool, washed in polluted water, or prepared by someone who is infected.
Amebiasis is more common and more severe in subtropical and tropical areas. It occurs more often when living conditions are crowded, sanitation is poor, and nutrition is inadequate.


What can be done to prevent the infection?

A person should eat only food that is unlikely to be contaminated, especially when traveling to tropical regions. This means eating only food that is well cooked and drinking bottled water. Hand washing after contact with dirty water or soil is important. Practicing safer sex will also help prevent the spread of amebiasis.


How is the infection diagnosed?

Amebiasis is usually identified by examining the stool. Several samples may need to be tested. Antibody titer blood tests may also be ordered.

Long Term Effects

What are the long-term effects of the infection?

A very severe amebiasis infection can lead to perforation or rupture of the colon. Rarely, the infection involves other organs in the body, such as the liver, brain, or lung.

Other Risks

What are the risks to others?

Someone who excretes cysts into his or her stool puts others at risk for amebiasis. Careful hand-washing and good sanitation help prevent the spread of this infection.


What are the treatments for the infection?

Medications such as iodoquinol (i.e., Yodoxin), paromomycin (i.e., Humatin), and diloxanide are used to kill the parasites in the intestines.
Other medications, such as metronidazole (i.e., Flagyl) followed by diiodohydroxyquin, or tinidazole (i.e. Tindamax) may be used to kill the organisms that have invaded the tissue. Surgery may be needed for complications such as perforation of the bowel.

Side Effects

What are the side effects of the treatments?

Side effects depend on the medication used. Metronidazole often causes nausea, vomiting, and diarrhea. Surgery carries a risk of bleeding, infection, and allergic reaction to anesthesia.

After Treatment

What happens after treatment for the infection?

Amebiasis is usually cured with medication, and the person can go back to normal activities.


How is the infection monitored?

Stool samples are examined 1, 3, and 6 months after treatment to be sure the person is free of the parasite. Any new or worsening symptoms should be reported to the healthcare provider.


The Merck Manual of Medical Information, 1997

Current Medical Diagnosis and Treatment, Tierney, 2000

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