Entamoeba

Entamoeba is a genus of Amoebozoa found as internal parasites or commensals of animals. In 1875, Fedor Lösch described the first proven case of amoebic dysentery in St. Petersburg, Russia. He referred to the amoeba he observed microscopically as Amoeba coli; however, it is not clear whether he was using this as a descriptive term or intended it as a formal taxonomic name. The genus Entamoeba was defined by Casagrandi and Barbagallo for the species Entamoeba coli, which is known to be a commensal organism. Lösch's organism was renamed Entamoeba histolytica by Fritz Schaudinn in 1903; he later died, in 1906, from a self-inflicted infection when studying this amoeba. For a time during the first half of the 20th century the entire genus Entamoeba was transferred to Endamoeba, a genus of amoebas infecting invertebrates about which little is known. This move was reversed by the International Commission on Zoological Nomenclature in the late 1950s, and Entamoeba has stayed 'stable' ever since.

==Species== Several species are found in humans and animals. Entamoeba histolytica is the pathogen responsible for invasive 'amoebiasis' (which includes amoebic dysentery and amoebic liver abscesses). Others such as Entamoeba coli (not to be confused with Escherichia coli) and Entamoeba dispar are harmless. With the exception of Entamoeba gingivalis, which lives in the mouth, and E. moshkovskii, which is frequently isolated from river and lake sediments, all Entamoeba species are found in the intestines of the animals they infect. Entamoeba invadens is a species that can cause a disease similar to E. histolytica but in reptiles. In contrast to other species, E. invadens forms cysts in vitro in the absence of bacteria and is used as a model system to study this aspect of the life cycle. Many other species of Entamoeba have been described, and it is likely that many others remain to be found.