Amoebiasis in the Tropics: Epidemiology and Pathogenesis

Abstract

Entamoeba histolytica is a protozoan parasite that causes amebic dysentery and liver abscess. The disease is common in tropical regions of the world where hygiene and sanitation is often approximate. The epidemiology of E. histolytica has been studied around the world. However, there is a dearth of comprehensive literature on the epidemiology of this pathogen as well as its pathogenicity in the tropical and underdeveloped regions of the world where the disease is actually more common. Epidemiological figures in many endemic tropical countries are often overestimated because of inaccurate identification. Accurate data on the prevalence of the pathogenic strain(s) of E. histolytica in those regions will allow for the effective cure of patients with anti-amoebic drugs thus preventing the development of resistant types and reducing management costs. With the advents of HIV and AIDS, several organisms have been identified as potential opportunistic pathogens. However, it is not clear whether amoebiasis is an opportunistic infection or not. Up to date, very little data has been published on the occurrence of E. histolytica in relation to HIV and AIDS. In developed countries amebiasis tends to be more common in older patients and occurs mostly among men who have sex with men or in institutions. However, in tropical regions, the epidemiology of amoebiasis is completely different and is more common among the general population and particularly among patients attending health care centers with diarrhea. Therefore, it is important to understand the epidemiology of this pathogen in tropical areas where it is responsible for most morbidity and mortality. The recent reclassification of E. histolytica into different species now including the pathogenic Entamoeba histolytica and the non pathogenic Entamoeba dispar and Entamoeba moshkovskii has further added to the complexity of the epidemiology of amoebiasis since these three species cannot be differentiated by microscopy that is the most commonly used diagnostic method particularly in tropical countries where resources are limited, but can only be differentiated by the use of molecular methods such as the polymerase chain reaction based methodologies. Recent development of simpler but more sensitive methods