Entamoeba histolytica

Last edited 02/2020

Amoebic dysentery is caused by Entamoeba histolytica, which is most often acquired in the tropics.

The organism invades the colonic mucosa creating shallow ulcers with undermined edges.

• Reservoir - Humans are the only known reservoir
  
  
• Epidemiology - Infections occur worldwide but are endemic in countries with poor sanitation; most UK cases are imported by travellers to endemic areas
  
  
• Transmission - Main route is through ingestion of contaminated food or water. Person-to-person transmission may also occur between household and sexual contacts via faecal-oral route
  
  
• Incubation period - Usually 2-4 weeks but may last months to several years



• Clinical features - 90% of cases are asymptomatic
• diarrhoea with or without dysentery occurs in intestinal disease- symptoms are often few or mild, with loose stools, mucus and blood - however may lead to fulminating colitis
• complications of this condition include severe colitis, perforation, localised amoeboma and liver abscess.

• amoebic liver abscess may occur which can be fatal
  
  
• Period of infectiousness - cases are considered infectious as long as cysts continue to be excreted which may last several years

Note:

• confirmation via PCR is important to distinguish between E. histolytica and non-pathogenic strains e.g. E. dispar

Reference:

• PHE (2019). Recommendations for the Public Health Management of Gastrointestinal Infections