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Amebiasis

• Amebiasis [am-e-BY-a-sis] is a parasitic infection of the large intestine.
• People get amebiasis from hand-to-mouth contact with surfaces or objects contaminated with stool from an infected person. People also get amebiasis when they swallow water or food contaminated with stool from an infected person.
• Amebiasis is treatable with antibiotics.
• To prevent amebiasis, follow careful handwashing and waste disposal practices. When traveling to tropical areas, follow safe food and water precautions.

   

What is amebiasis?

Amebiasis is a parasitic infection of the large intestine.

What is the infectious agent that causes amebiasis?

Amebiasis is caused by Entamoeba histolytica, a microscopic one-celled parasite. The parasite produces cysts that are passed in the stool of infected persons. The cysts can survive in the environment in water and food and on surfaces and objects.

Where is amebiasis found?

The parasite that causes amebiasis is found in the United States and around the world.

How do people get amebiasis?

People get amebiasis when they swallow Entamoeba histolytica cysts. This can happen by:

• Putting anything into the mouth that has touched the stool of an infected person
• Swallowing water or food that has been contaminated with Entamoeba histolytica
• Touching and bringing to the mouth cysts picked up from surfaces contaminated with Entamoeba histolytica

   

What are the signs and symptoms of amebiasis?

In most persons, the parasite lives in the intestine and does not cause illness, or causes mild intestinal symptoms. Symptoms of the mild form of amebiasis include loose or watery stools, abdominal tenderness or discomfort, and stomach cramps. Some people develop a severe form of amebiasis called AMEBIC DYSENTERY. Symptoms are stomach pain, bloody stools, and fever.

In rare cases, the parasite spreads outside the intestine to the liver and forms an abscess. Even less commonly, it spreads to other parts of the body, such as the lungs or brain.

How soon after exposure do symptoms appear?

Symptoms usually start within 1 to 4 weeks, but the time between infection and symptoms can be shorter or longer.

How is amebiasis diagnosed?

Infection is diagnosed by examining a stool sample under a microscope to look for the parasite. Because amebiasis can be difficult to diagnose, more than one stool sample might be needed.

A blood test is available but is recommended only if the patient's health-care provider thinks that the infection has invaded the wall of the intestines or some other organ, such as the liver. Blood tests might be positive if a person had an amebic infection in the past.

Who is at risk for amebiasis?

Anyone can get amebiasis, but it is most common in people who live in developing countries with poor sanitary conditions. In the United States, the disease is seen most often in immigrants from developing countries, men who have sex with men, and people who live in group settings or institutions that have poor sanitary conditions.

What is the treatment for amebiasis?

Several antibiotics are available to treat amebiasis. Treatment must be prescribed by a physician and can require more than one kind of medicine.

How common is amebiasis?

Amebiasis is common in tropical areas where living conditions are crowded and sanitation is poor.

How can amebiasis be prevented?

• Always wash hands thoroughly with soap and warm water after using the toilet, after changing diapers, before preparing food or drink, and before eating. When traveling in tropical countries where sanitation is poor, follow these precautions:
• Drink only bottled water, carbonated water, or canned or bottled sodas. Boiling water for 1 minute will kill parasites, bacteria, or viruses that might be present. Entamoeba histolytica is not killed by low doses of chlorine or iodine; do not rely on chemical water purification tablets, such as halide tablets, to prevent amebiasis.
• Be sure that food is cooked thoroughly to kill any parasites, bacteria, or viruses that might be present. Before eating raw vegetables that might be contaminated, wash them first with a strong detergent soap and then soak them in vinegar for 10-15 minutes.
• Do not eat fruit that has already been peeled or cut.
• Drink only pasteurized milk and dairy products.

   

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health-care provider. If you have any questions about the disease described above or think that you might have a parasitic infection, consult a health-care provider.

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