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A.D.A.M. Medical Encyclopedia [Internet]. Atlanta (GA): A.D.A.M.; 2013.

A.D.A.M. Medical Encyclopedia.

Amebiasis

Amebic dysentery; Intestinal amebiasis

Last reviewed: August 15, 2012.

Amebiasis is an infection of the intestines caused by the parasite Entamoeba histolytica.

Causes, incidence, and risk factors

Entamoeba histolytica can live in the large intestine (colon) without causing damage to the instestins. However, sometimes, it invades the colon wall, causing colitis, acute dysentery, or long-term (chronic) diarrhea. The infection can also spread through the blood to the liver and, rarely, to the lungs, brain, or other organs.

This condition occurs worldwide, but it is most common in tropical areas with crowded living conditions and poor sanitation. Africa, Mexico, parts of South America, and India have significant health problems associated with this disease.

Entamoeba histolytica is spread through food or water contaminated with stools. This contamination is common when human waste is used as fertilizer. It can also be spread from person to person -- particularly by contact with the mouth or rectal area of an infected person.

Risk factors for severe amebiasis include:

  • Alcoholism
  • Cancer
  • Older or younger age
  • Recent travel to a tropical region
  • Use of corticosteroid medication to suppress the immune system

In the United States, amebiasis is most common among those who live in institutions or people who have returned from travel to an area where amebiasis is common.

Symptoms

Most people with this infection do not have symptoms. If symptoms occur, they are seen 7 to 28 days after being exposed to the parasite.

Mild symptoms:

Severe symptoms:

  • Abdominal tenderness
  • Bloody stools
    • Passage of liquid stools with streaks of blood
    • Passage of 10 - 20 stools per day
  • Vomiting

Signs and tests

Examination of the abdomen may show liver enlargement or tenderness in the abdomen.

Tests include:

Treatment

Treatment depends on the severity of infection. Usually, metronidazole is given by mouth for 10 days. This is followed by paromomycin or diloxanide.

If you are vomiting, you may need to medications through a vein (intravenously) until you can take them by mouth. Medicines to stop diarrhea are usually not prescribed because they can make the condition worse.

After treatment, the stool should be rechecked to make sure that the infection has been cleared.

Expectations (prognosis)

The outcome is usually good with treatment. Usually, the illness lasts about 2 weeks, but it can come back if treatment is not given.

Complications

Calling your health care provider

Call your health care provider if you have persistent diarrhea.

Prevention

When traveling in tropical countries where poor sanitation exists, drink purified or boiled water and do not eat uncooked vegetables or unpeeled fruit. Public health measures include water purification, water chlorination, and sewage treatment programs.

References

  1. Petri WA Jr, Haque R. Amebiasis. In: Goldman L, Schafer AI,eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 360.
  2. Petri WA Jr, Haque R. Entamoeba species, including amebiasis.In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 273.
  3.  

Review Date: 8/15/2012.

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

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Copyright © 2013, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

What works?

  • Percutaneous needle aspiration does not seem to help patients with uncomplicated amoebic liver abscessesPercutaneous needle aspiration does not seem to help patients with uncomplicated amoebic liver abscesses
    Amoebiasis (disease caused by the protozoan Entameoba histolytica) remains an important clinical problem in countries around the world, with 40 to 50 million people affected. Mortality rates are significant, with 40,000 to 110,000 deaths each year. In fact, amoebiasis mortality is second only to malaria as cause of death from protozoan parasites. The most common complication of amoebiasis is the formation of a pus‐filled mass inside the liver (liver abscess). Metronidazole is the drug of choice for treatment of amoebic liver abscesses followed by a luminal agent to eradicate the asymptomatic carrier state. Cure rates are 95% with disappearance of fever, pain, and anorexia within 72 to 96 hours. This review compares the standard treatment with a more invasive alternative, where pus‐filled mass is drained by image‐guided percutaneous procedure (performed through the skin). Seven low quality randomised trials were included. All the seven studies included a total of 310 patients, but due to selective outcome reporting bias, less patients could be included in our analyses. Pooled analysis of three homogenous trials showed that needle aspiration did not significantly increase the proportion of patients with fever resolution. Benefits could be observed in resolution time of pain and tenderness. No additional benefit has been found with percutaneous needle aspiration plus metronidazole versus metronidazole alone for uncomplicated amoebic liver abscesses in hastening clinical and radiologic resolution. However, this conclusion is based on trials with methodological flaws and with insufficient sample sizes, and requires further confirmation in larger well‐designed, randomised trials.
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Figures

  • Amebic brain abscess.
    Digestive system.
    Digestive system organs.

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