Entamoeba and Entamoeba histolytica

Abstract

Entamoeba species are unicellular eukaryotes that parasitise all classes of vertebrates and some invertebrates. Only three species of Entamoeba have been proven to cause disease and sometimes death in their hosts: Entamoeba histolytica , a parasite of humans, Entamoeba nuttalli , a parasite of nonhuman primates and Entamoeba 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 with E. histolytica regardless of symptoms. Most cases of amoebiasis are asymptomatic, but E. histolytica can rarely cause intestinal or disseminated disease. Identification of E. histolytica is complicated by the existence of two morphologically identical amoebae that may also colonise the human intestinal tract, Entamoeba dispar and Entamoeba moshkovskii , neither of which are thought to cause disease. Entamoeba spp. are commonly studied to gain further insight into protozoal evolution, amoeboid locomotion and cell‐killing ability, among other topics. Key Concepts: Entamoeba species are unicellular eukaryotes in the supergroup Amoebozoa. Entamoeba species parasitise all classes of vertebrates and some invertebrates. The life cycle of most Entamoeba species consists of a motile, feeding and reproductive trophozoite stage and an environmentally resistant cyst stage responsible for transmitting the infection. Most Entamoeba species do not cause disease in their host and are considered commensal organisms. Entamoeba histolytica infection is referred to as amoebiasis regardless of whether or not symptoms are present. Most infections with E. histolytica in humans are asymptomatic, but E. histolytica can rarely cause dysentery or disseminated disease and is associated with significant human morbidity and mortality worldwide. Diagnosis and epidemiologic studies of E. histolytica are complicated by the presence of morphologically identical amoebae in human faeces. Entamoeba species are studied to gain insights into aspects of biology, including human disease, parasitism, evolution, cell locomotion and cell‐killing mechanisms.