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==Overview==
==Overview==
==Natural History, Complications and Prognosis==
==Natural History==
===Natural History===
===Luminal Amoebiasis (Asymptomatic)===
[[Image:Entamoeba histolytica life cycle-en.svg|thumb|left|250px|Life-cycle of the ''[[Entamoeba histolytica]]'']] 
*Following transmission, individuals typically remain asymptomatic for approximately 1 to 4 weeks (up to several years), during which the parasite starts to actively destroy to integrity of the intestinal wall.
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.
*The majority of colonized patients do not develop any clinical manifestations.  
Onset time is highly variable and the average asymptomatic infection persists for over a year. It is theorized that the absence of symptoms or their intensity may vary with such factors as strain of amoeba, immune response of the host, and perhaps associated bacteria and viruses.
*The infection rate of ''E. histolytica'' is approximately 10%-20%, whereas the infection rate of ''E. dispar'' is approximately 0% (since ''E. dispar'' is not associated with invasive disease).


===Complications===
===Invasive Intestinal Amoebiasis===
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.
*As the parasite continues to invade the intestinal wall, the integrity of the wall is compromised, and the host immune cells are activated. The activation of neutrophils, macrophages, lymphocytes, and eosinophils contribute to the inflammation and the development of clinical manifestations.
*The development of symptoms occurs gradually over 1-2 weeks. Early symptoms include profuse, watery diarrhea, abdominal pain, bloating, and nausea.
*If left untreated, the majority of patients report self-resolution of symptoms.
*In a minority of cases, however, the disease may progress and patients develop bloody diarrhea (dysentery), fulminant colitis, appendicitis, toxic megacolon, and ameboma (granulation tissue in the colon).
 
===Invasive Extraintestinal Amoebiasis===
*As the infection advances, the parasite is able to migrate outside the intestinal lumen into the bloodstream, where it is able to migrate to distant organs.
*If left untreated, the most site of parasitic migration is the liver, whereby the parasite travels in the portal circulation and causes amoebic liver abscess.
*Other organs may also be affected, including the brain (cerebral amoebiasis), pulmonary system (pleuropulmonary abscess), skin, and genitals.
 
===Chronic Amoebiasis===
*Patients with untreated amoebiasis may develop chronic disease.
*The symptoms of chronic amoebiasis resemble inflammatory bowel disease (IBD).
*The distinction between chronic amoebiasis vs. IBD is important since corticosteroid therapy is effective for IBD but worsens amoebiasis.
==Complications==
Complications of amoebiasis may be either intestinal or extraintestinal:
===Intestinal Complications===
*Dysentery
*Colitis
*Appendicitis<ref name="pmid23665815">{{cite journal| author=Otan E, Akbulut S, Kayaalp C| title=Amebic acute appendicitis: systematic review of 174 cases. | journal=World J Surg | year= 2013 | volume= 37 | issue= 9 | pages= 2061-73 | pmid=23665815 | doi=10.1007/s00268-013-2079-5 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23665815  }} </ref>
*Toxic megacolon
*Peritonitis
*Ameboma (granulation tissue in the colon)
*Intestinal perforation
 
===Extraintestinal Complications===
*Amoebic liver abscess
*Cerebral amoebiasis
*Pleuropulmonary abscess
*Skin lesions
*Amoebic genital lesions
*Amoebic pericarditis
 
==Prognosis==


''Entamoeba histolytica'' infection is associated with malnutrition and stunting of growth.<ref>{{cite journal | author=Mondal D, Petri Jr WA, Sack RB, ''et al.'' | title=''Entamoeba histolytica''-associated diarreal illness is negatively associated with the growth of preschool shildren: evidence from a  prospective study | journal=Trans R Soc Trop Med H | year=2006 | volume=100 |issue=11 | pages=1032&ndash;38 | doi=10.1016/j.trstmh.2005.12.012 }}</ref>
;Other complications
*[[Liver abscess]]
*[[Medication]] [[side effects]], including [[nausea]]
*Spread of the [[parasite]] through the [[blood]] to the [[liver]], [[lungs]], [[brain]],  or other [[organs]]
===Prognosis===
* The outcome is usually good with [[treatment]].


==References==
==References==

Latest revision as of 22:09, 11 March 2016

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Natural History

Luminal Amoebiasis (Asymptomatic)

  • Following transmission, individuals typically remain asymptomatic for approximately 1 to 4 weeks (up to several years), during which the parasite starts to actively destroy to integrity of the intestinal wall.
  • The majority of colonized patients do not develop any clinical manifestations.
  • The infection rate of E. histolytica is approximately 10%-20%, whereas the infection rate of E. dispar is approximately 0% (since E. dispar is not associated with invasive disease).

Invasive Intestinal Amoebiasis

  • As the parasite continues to invade the intestinal wall, the integrity of the wall is compromised, and the host immune cells are activated. The activation of neutrophils, macrophages, lymphocytes, and eosinophils contribute to the inflammation and the development of clinical manifestations.
  • The development of symptoms occurs gradually over 1-2 weeks. Early symptoms include profuse, watery diarrhea, abdominal pain, bloating, and nausea.
  • If left untreated, the majority of patients report self-resolution of symptoms.
  • In a minority of cases, however, the disease may progress and patients develop bloody diarrhea (dysentery), fulminant colitis, appendicitis, toxic megacolon, and ameboma (granulation tissue in the colon).

Invasive Extraintestinal Amoebiasis

  • As the infection advances, the parasite is able to migrate outside the intestinal lumen into the bloodstream, where it is able to migrate to distant organs.
  • If left untreated, the most site of parasitic migration is the liver, whereby the parasite travels in the portal circulation and causes amoebic liver abscess.
  • Other organs may also be affected, including the brain (cerebral amoebiasis), pulmonary system (pleuropulmonary abscess), skin, and genitals.

Chronic Amoebiasis

  • Patients with untreated amoebiasis may develop chronic disease.
  • The symptoms of chronic amoebiasis resemble inflammatory bowel disease (IBD).
  • The distinction between chronic amoebiasis vs. IBD is important since corticosteroid therapy is effective for IBD but worsens amoebiasis.

Complications

Complications of amoebiasis may be either intestinal or extraintestinal:

Intestinal Complications

  • Dysentery
  • Colitis
  • Appendicitis[1]
  • Toxic megacolon
  • Peritonitis
  • Ameboma (granulation tissue in the colon)
  • Intestinal perforation

Extraintestinal Complications

  • Amoebic liver abscess
  • Cerebral amoebiasis
  • Pleuropulmonary abscess
  • Skin lesions
  • Amoebic genital lesions
  • Amoebic pericarditis

Prognosis

References

  1. ↑ Otan E, Akbulut S, Kayaalp C (2013). "Amebic acute appendicitis: systematic review of 174 cases". World J Surg. 37 (9): 2061–73. doi:10.1007/s00268-013-2079-5. PMID 23665815.


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