EntamoebaSpecies andEntamoeba histolytica

Abstract Entamoebaspecies are unicellular eukaryotes that parasitise all classes of vertebrates and some invertebrates. Only three species ofEntamoebahave been proven to cause disease and sometimes death in their hosts:Entamoeba histolytica, a parasite of humans,Entamoeba nuttalli, a parasite of nonhuman primates andEntamoeba invadens, a parasite of reptiles. Other species appear to live as commensals in their hosts and do not cause evident disease. Amoebiasis is defined as infection withE. histolytica. Most cases of amoebiasis are asymptomatic, butE. histolyticacan cause intestinal or disseminated disease. Identification ofE. histolyticais complicated by the existence of three morphologically identical amoebae that may also colonise the human intestinal tract,Entamoeba dispar,Entamoeba bangladeshiandEntamoeba moshkovskii, none of which have been proven to cause disease (although the potential for pathogenicity in the latter two is not fully understood).Entamoebaspp. are commonly studied to gain further insight into protozoal evolution, amoeboid locomotion and cell‐killing ability, amongst other topics. Key Concepts Entamoebaspecies are unicellular eukaryotes in the supergroup Amoebozoa. Entamoebaspecies parasitise all classes of vertebrates and some invertebrates. The life cycle of mostEntamoebaspecies consists of a motile, feeding and reproductive trophozoite stage and an environmentally resistant cyst stage responsible for transmitting the infection. MostEntamoebaspecies do not cause disease in their host and are considered commensal organisms. Entamoeba histolyticainfection is referred to as amoebiasis regardless of whether symptoms are present. Most infections withE. histolyticain humans are asymptomatic, butE. histolyticacan rarely cause dysentery or disseminated disease and is associated with significant human morbidity and mortality worldwide. Diagnosis and epidemiologic studies ofE. histolyticaare complicated by the presence of morphologically identical amoebae in human faeces. Entamoebaspecies are studied to gain insights into aspects of biology, including human disease, parasitism, evolution, cell locomotion and cell‐killing mechanisms.