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This article is about the infection. For the Amoebic Ensemble album, see Amoebiasis (album).
Classification and external resources
Entamoeba histolytica life cycle-en.svg
Life-cycle of the Entamoeba histolytica
ICD-10 A06
ICD-9 006
DiseasesDB 4304
MedlinePlus 000298
eMedicine article/212029 article/996092
MeSH D000562

Amoebiasis, or Amebiasis, refers to infection caused by the amoeba Entamoeba histolytica.[1][2] The term entamoebiasis is occasionally seen but is no longer in use;[citation needed] it refers to the same infection.


Signs and symptoms[edit]

Most infected people, about 90%,[5] are asymptomatic, but this disease has the potential to make the sufferer dangerously ill. It is estimated that about 40,000 to 100,000 people worldwide die annually due to amoebiasis.[6]

Infections can sometimes last for years. Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks. Symptoms can range from mild diarrhea to severe dysentery with blood and mucus. The blood comes from lesions formed by the amoebae invading the lining of the large intestine. In about 10% of invasive cases the amoebae enter the bloodstream and may travel to other organs in the body. Most commonly this means the liver, as this is where blood from the intestine reaches first, but they can end up almost anywhere in the body.


In asymptomatic infections the amoeba lives by eating and digesting bacteria and food particles in the gut, a part of the gastrointestinal tract.[citation needed] It does not usually come in contact with the intestine itself due to the protective layer of mucus that lines the gut. Disease occurs when amoeba comes in contact with the cells lining the intestine. It then secretes the same substances it uses to digest bacteria, which include enzymes that destroy cell membranes and proteins. This process can lead to penetration and digestion of human tissues, resulting first in flask-shaped ulcers in the intestine. Entamoeba histolytica ingests the destroyed cells by phagocytosis and is often seen with red blood cells (a process known as erythrophagocytosis) inside when viewed in stool samples. Especially in Latin America,[citation needed] a granulomatous mass (known as an amoeboma) may form in the wall of the ascending colon or rectum due to long-lasting immunological cellular response, and is sometimes confused with cancer.[7]

"Theoretically, the ingestion of one viable cyst can cause an infection."[8]


Amoebiasis is an infection caused by the amoeba Entamoeba histolytica Likewise amoebiasis is sometimes incorrectly used to refer to infection with other amoebae, but strictly speaking it should be reserved for Entamoeba histolytica infection. Other amoebae infecting humans include:[9]








Amoebae in a colon biopsy from a case of amoebic dysentery.




Amoebic Ulcer Intestine

To help prevent the spread of amoebiasis around the home :

To help prevent infection:

  • Boil water or treat with iodine tablets.

Good sanitary practice, as well as responsible sewage disposal or treatment, are necessary for the prevention ofE.histolytica infection on an endemic level. E.histolytica cysts are usually resistant to chlorination, therefore sedimentation and filtration of water supplies are necessary to reduce the incidence of infection.[15]



Main article: Amoebicide

E. histolytica infections occur in both the intestine and (in people with symptoms) in tissue of the intestine and/or liver.[14] As a result, two different classes of drugs are needed to treat the infection, one for each location. Such anti-amoebic drugs are known as amoebicides.


In the majority of cases, amoebas remain in the gastrointestinal tract of the hosts. Severe ulceration of the gastrointestinal mucosal surfaces occurs in less than 16% of cases. In fewer cases, the parasite invades the soft tissues, most commonly the liver. Only rarely are masses formed (amoebomas) that lead to intestinal obstruction.(Mistaken for Ca caecum and appendicular mass) Other local complications include bloody diarrhea, pericolic and pericaecal abscess.

Complications of hepatic amoebiasis includes subdiaphragmatic abscess, perforation of diaphragm to pericardium and pleural cavity, perforation to abdominal cavital (amoebic peritonitis) and perforation of skin (amoebic cutis).

Pulmonary amoebiasis can occur from hepatic lesion by haemotagenous spread and also by perforation of pleural cavity and lung. It can cause lung abscess, pulmono pleural fistula, empyema lung and broncho pleural fistula. It can also reach brain through blood vessel and cause amoebic brain abscess and amoebic meningoencephalitis. Cutaneous amoebiasis can also occur in skin around sites of colostomy wound, perianal region, region overlying visceral lesion and at the site of drainage of liver abscess.

Urogenital tract amoebiasis derived from intestinal lesion can cause amoebic vulvovaginitis (May's disease), rectovesicle fistula and rectovaginal fistula.

Entamoeba histolytica infection is associated with malnutrition and stunting of growth.[17]


As of 2010 it caused about 55,000 deaths down from 68,000 in 1990.[18] In older textbooks it is often stated that 10% of the world's population is infected with Entamoeba histolytica.[citation needed] It is now known that at least 90% of these infections are due to E. dispar.[citation needed] Nevertheless, this means that there are up to 50 million true E. histolytica infections and approximately seventy thousand die each year, mostly from liver abscesses or other complications. Although usually considered a tropical parasite, the first case reported (in 1875) was actually in St Petersburg in Russia, near the Arctic Circle.[19] Infection is more common in warmer areas, but this is both because of poorer hygiene and the parasitic cysts surviving longer in warm moist conditions.[14]

The most dramatic incident in the USA was the Chicago World's Fair outbreak in 1933 caused by contaminated drinking water; defective plumbing permitted sewage to contaminate water.[20] There were 1,000 cases (with 58 deaths). In 1998 there was an outbreak of amoebiasis in the Republic of Georgia.[21] Between 26 May and 3 September 1998, 177 cases were reported, including 71 cases of intestinal amoebiasis and 106 probable cases of liver abscess.

See also[edit]


  2. ^ WHO (1997). "WHO/PAHO/UNESCO report. A consultation with experts on amoebiasis. Mexico City, Mexico 28–29 January 1997.". Epidemiological Bulletin 18 (1): 13–14. PMID 9197085. 
  3. ^ WHO (1998). Life in the 21st Century: a vision for all. The World Health Report 1998. World Health Organization, Geneva, Switzerland. 
  4. ^ Haque R, Mondal D, Duggal P, et al. (2006). "Entamoeba histolytica infection in children and protection from subsequent amebiasis". Infection and Immunity 74 (2): 904–909. doi:10.1128/IAI.74.2.904-909.2006. PMC 1360358. PMID 16428733. 
  5. ^ "Amebiasis". NEJM. United States NEJM: Massachusetts Medical Society. 2003-04-17. Retrieved 2012-04-12. 
  6. ^ Atlas of Human Infectious Diseases, First Edition. Heiman F.L. Wertheim, Peter Horby and John P. Woodall., 2012, Blackwell Publishing Ltd.
  7. ^ Day, David W.; Basil C. Morson; Jeremy R. Jass; Geraint Williams; Ashley B. Price (2003). Morson and Dawson's Gastrointestinal Pathology. John Wiley & Sons, Inc. ISBN 978-0-632-04204-3. 
  8. ^ "Foodborne Pathogenic Microorganisms and Natural Toxins Handbook: Entamoeba histolytica". Bad Bug Book. United States Food and Drug Administration: Center for Food Safety & Applied Nutrition. 2007-12-28. Archived from the original on 9 July 2009. Retrieved 2009-07-13. 
  9. ^ Berger SA, Marr JS. Human Parasitic Diseases Sourcebook. Jones and Bartlett Publishers: Sudbury, Massachusetts, 2006.
  12. ^ " Keratitis: 39-year-old contact lens wearer with persisting keratitis & pain". Archived from the original on 5 December 2008. Retrieved 2009-01-17. 
  16. ^ "FDA Bacteriological Analytical Manual". Archived from the original on 6 April 2008. Retrieved 2008-03-26. 
  17. ^ Mondal D, Petri Jr WA, Sack RB, et al. (2006). "Entamoeba histolytica-associated diarrheal illness is negatively associated with the growth of preschool shildren: evidence from a prospective study". Trans R Soc Trop Med H 100 (11): 1032–38. doi:10.1016/j.trstmh.2005.12.012. PMID 16730764. 

External links[edit]