Amebiasis

Amebiasis is an infection of the large intestines caused by Entamoeba histolytica, a 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. The infection is also a sexually transmitted disease, 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 are the signs and symptoms of the infection?

The illness may produce no symptoms at all, or may produce only very mild ones. The symptoms may be so vague, they are not noticed, and may include:

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.

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 keeping to food that is well cooked and water that is bottled. Practicing safer sex will also help prevent the spread of amebiasis.

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.

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 ioloquinol, paromomycin, and diloxanide are used to kill the parasites in the intestines. Other medications, such as metronidazole, may be used to kill the organisms that have invaded the tissue. Surgery may be needed for complications like perforation of the bowel.

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.

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.