Amebiasis (Amebic Dysentery)

Amebiasis is an infection, usually in the intestines, that is caused by a microscopic parasite, Entamoeba histolytica. In 2008, there were 410 cases reported among New York City residents (rate of 5.0 cases per 100,000 persons).

Who gets amebiasis?

Anyone can get amebiasis, but it occurs more often in people who have traveled to developing countries, people who live in institutions that have poor sanitary conditions, and men who have sex with men.

How is amebiasis spread?

Amebiasis can occur when a person ingests the cyst (or egg-like) stage of the parasite in contaminated food or water. It can also be spread by person-to-person contact, by putting anything into the mouth that has touched the stool (feces) of a person who is infected with Entamoeba histolytica.

What are the symptoms of amebiasis?

People exposed to this parasite may experience mild or severe symptoms, or no symptoms at all. Fortunately, most exposed people do not become seriously ill. The mild form of amebiasis includes nausea, loose stools, and stomach pain and stomach cramping. Amebic dysentery is a severe form of amebiasis associated with frequent stools with blood or mucus, stomach pain, and fever. Rarely, the parasite will invade the body beyond the intestines and cause a more serious infection, such as a liver abscess.

How soon after infection do symptoms appear?

The symptoms may appear within a few days to a few months after exposure but usually within two to four weeks.

For how long can an infected person carry amebiasis?

Some people with amebiasis may carry the parasite for weeks to years, often without symptoms.

How is amebiasis diagnosed?

If your doctor suspects amebiasis he/she will check your stool for the parasite. Diagnosis is made by examining the stool under a microscope or by using special detection tests for Entamoeba histolytica. Sometimes, several stool samples taken on different days are needed, since the number of amoeba shed in the stool varies from day to day.

What is the treatment for amebiasis?

Specific antibiotics such as metronidazole can be prescribed by a doctor to treat amebiasis.

Should an infected person be excluded from work or school?

It depends. Since the Entamoeba histolytica parasite is passed in the stool, people with active diarrhea who are unable to control their bowel habits (for example, infants, young children, and certain disabled individuals) may need to be excluded from group settings where they present a risk to others. Most infected people may return to work or school when their stools become formed as long as they wash their hands thoroughly after using the toilet. Food handlers, certain health care workers, children in day care, pre-kindergarten or kindergarten, and employees in day care, pre-kindergarten and kindergarten must obtain approval from the Health Department before returning to their routine activities, even if they are not having diarrhea. This requires follow-up stool testing to be sure that they are no longer infectious.

How can amebiasis be prevented?

The most important preventive measures include:

Practice good hygiene.

  • Always thoroughly wash your hands with soap and warm running water before touching food, after using the toilet or changing diapers, after handling animal stools, and after gardening or other direct contact with soil.
  • If you work in a child-care center where you change children's diapers, wash your hands carefully between changing each child's diapers. When using gloves, wash your hands and change gloves between each child.
  • If you take care of persons with amebiasis, or persons who have diarrhea, wash your hands after bathing patients, emptying bedpans, changing soiled linen, or otherwise coming in contact with stool.

Avoid water that may be contaminated.

  • Do not drink water directly from streams, lakes, springs or swimming pools.
  • Heat water to a rolling boil for 1 minute whenever you are unsure of the safety of a drinking water source, or use a water filter that has an absolute pore size of 1 micron or smaller, or one that has been National Sanitation Foundation (NSF) rated for "cyst removal."
  • Carefully dispose of sewage wastes so as not to contaminate surface water or ground water.
  • Comply fully with water advisories whenever issued by public health or government authorities.

Avoid food that may be contaminated.

  • Uncooked fruits and vegetables should be washed thoroughly before being eaten. Take extra care when traveling.
  • If you travel to developing countries, you may be at greater risk for amebiasis because of poorer water treatment and food sanitation. Warnings about food, drinks and swimming are even more important when visiting developing nations. Avoid raw (uncooked) fruits and vegetables that you did not wash or peel yourself, unboiled tap water, ice made from unboiled tap water, and items purchased from street vendors.

Protect yourself and others.

  • If you have amebiasis, wash your hands often to prevent spreading the disease to other people.
  • Sexual practices that may result in hand or mouth contact with stool, such as anal sex, touching the anus, or oral-anal sex ("rimming"), increase the risk for amebiasis transmission. Risk of transmission may be decreased by washing thoroughly with soap and water before and after any anal contact, and by using a barrier such as a dental dam or household plastic wrap during oral-anal contact. Persons who are infected with amebiasis, or any diarrheal illness, should refrain from sexual activity that may expose a partner to their stool until they are effectively treated.