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Other namesAmoebic dysentery, amebiasis, entamoebiasis[1][2]
Amebiasis LifeCycle.gif
The life-cycle of various intestinal Entamoeba species
SpecialtyInfectious disease
SymptomsBloody diarrhea, abdominal pain[3]
ComplicationsSevere colitis, colonic perforation, anemia[3]
CausesAmoebas of the Entamoeba group[3]
Diagnostic methodStool examination, antibodies in the blood[3]
Differential diagnosisBacterial colitis[3]
PreventionImproved sanitation[3]
TreatmentTissue disease: metronidazole, tinidazole, nitazoxanide, dehydroemetine, chloroquine,
Intestinal infection: diloxanide furoate, iodoquinoline[3]
Frequency>480 million[3]





Signs and symptomsEdit

Most infected people, about 90%,[6] are asymptomatic, but this disease has the potential to become serious. It is estimated that about 40,000 to 100,000 people worldwide die annually due to amoebiasis.[7]

Infections can sometimes last for years if there is no treatment. 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 dysentery with blood, coupled with intense abdominal pains. The blood comes from bleeding lesions created by the amoebae invading the lining of the colon. 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,[8] as this is where blood from the intestine reaches first, but they can end up almost anywhere in the body.



The ingestion of one viable cyst may cause an infection.[10]

Steroid therapy can lead to severe amoebic colitis in persons with asymptomatic or symptomatic E. histolytica infection.[11] Severe amoebic colitis is associated with high mortality, and on average more than 50% with severe colitis die.[12]





Life-cycle of the Entamoeba histolytica




Amoebiasis results from tissue destruction induced by the E. histolytica parasite. E. histolytica causes tissue damage by three main events: direct host cell killing, inflammation, and parasite invasion.[19]


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

With colonoscopy it is possible to detect small ulcers of between 3–5mm, but diagnosis may be difficult as the mucous membrane between these areas can look either healthy or inflamed.[3] Trophozoites may be identified at the ulcer edge or within the tissue, using immunohistochemical staining with specific anti-E. histolytica antibodies.[5]



Immunohistochemical staining of trophozoites (brown) using specific anti–Entamoeba histolytica macrophage migration inhibitory factor antibodies in a patient with amebic colitis.


Stool antigen detection tests have helped to overcome some of the limitations of stool microscopy. Antigen detection tests are easy to use, but they have variable sensitivity and specificity, especially in low-endemic areas.[5]

Polymerase chain reaction (PCR) is considered the gold standard for diagnosis but remains underutilized.[5]


Specimen of the human intestine that was damaged by amebic ulcer.

To help prevent the spread of amoebiasis around the home :

To help prevent infection:

  • Boil water or treat with iodine tablets.




E. histolytica infections occur in both the intestine and (in people with symptoms) in tissue of the intestine and/or liver.[18] Those with symptoms require treatment with two medications, an amoebicidal tissue-active agent and a luminal cysticidal agent. Individuals that are asymptomatic only need a luminal cysticidal agent.[5]






Entamoeba histolytica infection is associated with malnutrition and stunting of growth.[22]


Amoebiasis caused about 55,000 deaths worldwide in 2010, down from 68,000 in 1990.[23] 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.[24] Infection is more common in warmer areas, but this is because of both poorer hygiene and the parasitic cysts surviving longer in warm moist conditions.[18]


Amoebiasis was first described by Lösh in 1875, in northern Russia.[3] The most dramatic incident in the US was the Chicago World's Fair outbreak in 1933, caused by contaminated drinking water. There were more than a thousand cases, with 98 deaths.[25][26] It has been known since 1897 that at least one non-disease-causing species of Entamoeba existed (Entamoeba coli), but it was first formally recognized by the WHO in 1997 that E. histolytica was two species, despite this having first been proposed in 1925.[3] In addition to the now-recognized E. dispar, evidence shows there are at least two other species of Entamoeba that look the same in humans: E. moshkovskii and Entamoeba bangladeshi.[3] The reason these species haven't been differentiated until recently is because of the reliance on appearance.[3]

Joel Connolly of the Chicago Bureau of Sanitary Engineering brought the outbreak to an end when he found that defective plumbing permitted sewage to contaminate drinking water. In 1998 there was an outbreak of amoebiasis in the Republic of Georgia.[27] Between 26 May and 3 September 1998, 177 cases were reported, including 71 cases of intestinal amoebiasis and 106 probable cases of liver abscess.



  5. ^ a b c d e Shirley DT, Farr L, Watanabe K, Moonah S (July 2018). "A Review of the Global Burden, New Diagnostics, and Current Therapeutics for Amebiasis". Open Forum Infectious Diseases. 5 (7): ofy161. doi:10.1093/ofid/ofy161. PMC 6055529. PMID 30046644.
  6. ^ Haque R, Huston CD, Hughes M, Houpt E, Petri WA (April 2003). "Amebiasis". The New England Journal of Medicine. 348 (16): 1565–73. doi:10.1056/NEJMra022710. PMID 12700377.
  8. ^ a b Nespola B, Betz V, Brunet J, Gagnard JC, Krummel Y, Hansmann Y, et al. (2015). "First case of amebic liver abscess 22 years after the first occurrence". Parasite. 22: 20. doi:10.1051/parasite/2015020. PMC 4472968. PMID 26088504. Archived from the original on 2015-09-24.  
  11. ^ Shirley DA, Moonah S (July 2016). "Fulminant Amebic Colitis after Corticosteroid Therapy: A Systematic Review". PLoS Neglected Tropical Diseases. 10 (7): e0004879. doi:10.1371/journal.pntd.0004879. PMC 4965027. PMID 27467600.
  14. ^ Visvesvara GS, Moura H, Schuster FL (June 2007). "Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea". FEMS Immunology and Medical Microbiology. 50 (1): 1–26. doi:10.1111/j.1574-695X.2007.00232.x. PMID 17428307. Archived from the original on 2013-01-05.
  17. ^ Recavarren-Arce S, Velarde C, Gotuzzo E, Cabrera J (March 1999). "Amoeba angeitic lesions of the central nervous system in Balamuthia mandrilaris amoebiasis". Human Pathology. 30 (3): 269–73. doi:10.1016/S0046-8177(99)90004-7. PMID 10088544.
  18. ^ a b c Ryan KJ, Ray CG, eds. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 733–8. ISBN 978-0-8385-8529-0.
  19. ^ Ghosh S, Padalia J, Moonah S (21 January 2019). ": Cell Death, Inflammation, Invasion, and the Gut Microbiome". Current Clinical Microbiology Reports. 6 (1): 51–57. doi:10.1007/s40588-019-0113-6. PMC 6449278. PMID 31008019.
  21. ^ "FDA Bacteriological Analytical Manual". Archived from the original on 2008-04-06. Retrieved 2008-03-26.
  22. ^ Mondal D, Petri WA, Sack RB, Kirkpatrick BD, Haque R, et al. (November 2006). "Entamoeba histolytica-associated diarrheal illness is negatively associated with the growth of preschool children: evidence from a prospective study". Transactions of the Royal Society of Tropical Medicine and Hygiene. 100 (11): 1032–8. doi:10.1016/j.trstmh.2005.12.012. PMID 16730764.
  25. ^ Markell EK (June 1986). "The 1933 Chicago outbreak of amebiasis". The Western Journal of Medicine. 144 (6): 750. PMC 1306777. PMID 3524005.
  27. ^ Kreidl P, Imnadze P, Baidoshvili L, Greco D (October 1999). "Investigation of an outbreak of amoebiasis in Georgia". Euro Surveillance. 4 (10): 103–104. doi:10.2807/esm.04.10.00040-en. PMID 12631887. Archived from the original on 2007-08-13.

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