ENTAMOEBA-HISTOLYTICA AND ENTAMOEBA-DISPAR ARE DISTINCT SPECIES - CLINICAL, EPIDEMIOLOGIC AND SEROLOGICAL EVIDENCE

The name of the causative organism of invasive amoebiasis, Entamoeba h istolytica, was first introduced in 1903, even though this intestinal amoeba had been recognised since 1875. The marked disparity between th e number of infected individuals and those with invasive amoebiasis re sulted in a number of explanatory hypotheses being proposed. Although none of these were universally accepted, Brumpt's concept [1] of two m orphologically identical species gained increasing acceptance 50-60 ye ars later when technology became available to investigate this anomaly . Sargeaunt spear-headed this drive by establishing the value of isoen zyme electrophoresis for studying the host-parasite relationship. From this foundation, incorporation of clinical, epidemiological and serol ogical parameters to studies of the parasite resulted in the conclusio n that a species complex comprising two morphologically identical amoe bae was implicated with the disease. The two organisms have been named E. histolytica and Entamoeba dispar. The former is a pathogen and is responsible for invasive amoebiasis, while the latter is a gut commens al. Demonstration of the existence of this species complex has subsequ ently been confirmed by studies on the nucleic acids from several inde pendent laboratories. The acceptance of E. histolytica and E. dispar a s distinct species has had a major impact on our understanding of amoe biasis and its clinical management. (C) 1998 Australian Society for Pa rasitology. Published by Elsevier Science Ltd.