Amebiasis Patient Information Fact Sheet

What is amebiasis?
Amebiasis is an infection of the gut caused by a parasite called Entamoeba histolytica, which is found in most tropical areas. Most people who live in these areas have some form of parasite living within their intestine, but in many cases the parasites will not cause any serious harm. Amebiasis may be present in the local population, who will usually have no symptoms but nevertheless can pass the parasite to others. Travelers to tropical countries are therefore at high risk of contracting some form of parasite, which may cause serious illness.

What are the symptoms of amebiasis?
Amoebas such as E. histolytica usually live in the large intestine. If they live on the surface of the intestine there will usually be no symptoms. But if the parasite invades the wall of the large intestine and forms a cyst, this may cause ulceration and bleeding. Recurrent bouts of diarrhea will also occur, with the appearance of blood and slimy mucus in the bowel movements. An infected person can become dehydrated if he or she doesn't drink enough fluid to replace the fluid lost from the diarrhea. Unlike diarrhea caused by bacteria, amebic diarrhea has a gradual onset and does not usually cause the high fever associated with bacterial infections. Amebic liver abscesses can sometimes occur in people with amebic diarrhea, but in most cases they will not be accompanied by any bowel symptoms. Cysts travel from the intestine to the liver in about one in five cases of amebiasis, but abscess formation is uncommon. Abscesses cause severe pain over the liver and a high fever. They can be dangerous and need urgent medical treatment. Once a person is infected, amoebas will persist in the intestine for months or years and, although there may be no symptoms for a long time, it is still possible to develop illness many years later. The amoebas pass out of the body as cysts, which can then infect another person. Carriers with no symptoms should be treated to prevent both future illness and the risk of infecting other people with the parasite.

How is amebiasis treated?
If a person has no symptoms but a stool sample confirms the presence of amebic cysts, medical treatment will be prescribed. Metronidazole (Flagyl), a type of antibiotic, may be given for traveler's diarrhea, liver abscess or for other forms of amebic disease. It may also be prescribed to eradicate the parasite in carriers with no symptoms. Tinidazole (Tindamax) is another antibiotic that may be prescribed as an alternative to metronidazole. Chloroquine (Aralen) tablets may be used to treat amebic hepatitis. Rehydration is very important in treatment. Electrolyte solutions (Ceralyte) can be taken to replace fluid and salts that are lost as a result of the diarrhea. Plenty of clear liquids such as water or juice should also be taken.

How is amebiasis prevented?
It is important to be careful about food in tropical countries where all forms of travelers' diarrhea may occur:

  • Avoid foods that may have been cooked some time before. Freshly boiled food (eg, rice and sweet corn) is safe to eat.
  • Avoid salads, shellfish, crab and prawns.
  • Avoid fruit and vegetables that can't be peeled; fruits that can be peeled, eg, avocado, bananas, citrus fruits and melon, are safe.
  • Forgo ice in drinks and drink only bottled water. Do not use tap water, even for brushing teeth.

If a traveler has spent a long time in tropical countries, it may be advisable for them to have a stool test upon returning, as amoebae may be present without symptoms and may require treatment.

Further information
Centers for Disease Control and Prevention: http://www.cdc.gov/parasites/amebiasis/
PubMed Health: www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001343/
NY Department of Health: www.health.ny.gov/diseases/communicable/amebiasis/fact_sheet.htm

Last Reviewed: May 2013