Amoebiasis

Entamoeba histolytica has been one of the most reported parasitic diseases of immunocompetent hosts in Canada and Alaska. Those at highest risk for symptomatic E. histolytica infection are travellers returning from the developing world and native North Americans. In the past, the overall prevalence of amoebic infection in Canada and Alaska was estimated at 1% (Burrows 1961). More recent data from Canada suggests a rate of 6.8 (reported) cases per 100 000 population, with a male to female ratio of almost 2:1, the majority in adults (CCDR 1996). Endemic amoebic disease has most often been observed in native populations. For example, communities in the Loon Lake region of Saskatchewan were reported to be at the centre of an area of endemicity which expanded to involve large parts of Alberta and the Northwest Territories from 1956 to 1973. The new technologies to distinguish between E. histolytica and E. dispar have not yet been applied in Canada and Alaska. It is very likely that once these tests are routinely available, a large majority of the asymptomatic individuals reported to have E. histolytica will prove to have E. dispar only. Published surveillance reports typically do not distinguish symtomatic disease (presumed E. histolytica) and asymptomatic cyst carriage (possibly E. histolytica, but much more likely E. dispar). As a result, the carriage prevalences cited earlier are certainly an overestimate of the true E. histolytica levels in the population.

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