Amoebiasis

Amoebiasis is a condition in which your gut (intestines) becomes infected with the parasite E. histolytica. Entamoebae are a group of single-celled parasites (living things that live in, or on, other living organisms) that can infect both humans and some animals. There are at least six species of entamoeba that can infect the human gut but only E. histolytica causes disease.

Amoebiasis is caused by the protozoan Entamoeba histolytica.

  • Amoebiasis is often asymptomatic but may cause dysentery and invasive extra-intestinal disease.
  • Entamoeba dispar, another species, has been thought in the past to be non-pathological but in vitro and in vivo experiments suggest it is capable of causing liver damage.
  • Humans are the only reservoir, and infection occurs by ingestion of mature cysts in food or water, or on hands contaminated by faeces.
  • The cysts of E. histolytica enter the small intestine and release active amoebic parasites (trophozoites), which invade the epithelial cells of the large intestines, causing flask-shaped ulcers. Infection can then spread from the intestines to other organs - eg, the liver, lungs and brain, via the venous system.
  • Asymptomatic carriers pass cysts in the faeces and the asymptomatic carriage state can persist indefinitely. E. dispar is the parasite most commonly found in such carriers, Cysts remain viable for up to two months.
  • Invasive amoebiasis most often causes an amoebic liver abscess but may affect the lung, heart, brain, urinary tract and skin.

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