Entamoeba histolyticadispar

Ewert Linder

Entamoeba histolytica infects humans and some higher non-human primates. It is thought to cause an estimated 40000-100000 deaths annually. Intestinal infection with E. histolytica - and the associated severe manifestations of invasive amoebiasis - is a global problem, but the true prevalence of the intestinal infection in the northern countries - as indeed globally - is not known. The reason for this is that available prevalence figures, to a large extent, have been based on laboratory findings of 'E. histolytica cysts' in faeces. This finding needs to be related to the recent observation that the majority of such cysts can be identified as non-pathogenic Entamoeba dispar. Entamoeba histolytica and E. dispar are morphologically indistinguishable (Diamond and Clark 1993). The two species have previously been called pathogenic and non-pathogenic E. histolytica.

The laboratory techniques for distinguishing E. histolytica and E. dispar are available but not yet in general use. Thus, even if the available information is sufficient to estimate the health impact of E. histolytica infection, we will only slowly, with the development of more widely available laboratory diagnostics, become aware of the prevalence of the infection in areas with few cases of clinical disease, as in the northern areas we are dealing with in this chapter.

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