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Entamoeba

Life > Eukaryotes > Amoebozoa > Entamoebida

Single-celled organisms that fall within the amoeba functional group and which are parasites or commensals of all major groups of vertebrates as well as a few invertebrates.  The life cycle typically consists of an infective cyst stage and a multiplying trophozoite stage. Worldwide, Entamoeba histolitica, which causes amoebic dysentery and amoebic liver abscess, is the third most death-causing parasitic disease after malaria and schistosomiasis, with 50 000 to 100 000 deaths caused annually.

Whole genome sequencing of Entamoeba histolitica as well as other Entamoeba species is taking place (see Links).

Genetic methods are becoming increasingly important in helping to distinguish the different species of Entamoeba. This is important as some species cause disease (e.g. Entamoeba histolitica) whereas others don't, and one needs to know the difference in order to assess treatment action. Up to six species of Entamoeba have been found in humans.

Some species likely to be encountered in southern Africa

Entamoeba coli

A commensal species that does not cause disease, found in the intestinal tract of humans and other animals.

 

Entamoeba dispar

Entamoeba histolitica in the old sense, has been found to be made up of two species: true Entamoeba histolitica (previously known as 'pathogenic E. histolytica') and Entamoeba dispar (previously known as 'non-pathogenic E. histolytica'). As the terms suggest, Entamoeba dispar does not cause disease, but it is commonly found in humans and other animals, in fact more commonly so than Entamoeba histolitica.

 

Entamoeba gingivalis

Lives in the mouth (teeth, gums, tonsils) of humans and other animals (e.g. primates, dogs and cats)  where it eats bacteria and blood cells (leukocytes and erythrocytes). Note that the gum disease called gingivitis, which causes inflamation of the gums, is caused by bacteria rather than Entamoeba gingivalis. However, the presence of the latter is normally associated with poor oral hygiene which in turn is associated with heavy plaque (bacterial biofilms) and gingivitis.

 

Entamoeba histolitica

The cause of amoebic dysentery and amoebic liver abscess in humans and also infects other animals such as dogs, pigs and cattle. Transmission is through the consumption of cysts in faecal-infected water or food

 

Entoamoeba invadens

A intestinal parasite of reptiles such as snakes and lizards that causes disease similar to that caused by Entamoeba histolitica. Also found in turtles but does not seem to cause disease in these animals.

 

Entamoeba moshkovskii

This species has become secondarily free-living and is commonly found worldwide in anoxic sediments such as are found in sewage pans and the bottoms of muddy rivers. However, is can also be found in clean river sediments and in brackish coastal pools. It is rarely found in humans and in such cases has not caused sickness.

 

Entamoeba terrapinae

A commensal species found in turtles.

 

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