Population structure and genetic typing of Trypanosoma cruzi, the agent ofChagas disease: a multilocus enzyme electrophoresis approach

A set of 434 Trypanosoma cruzi stocks from a wide ecogeographical range was analysed by Multilocus Enzyme Electrophoresis for 22 genetic loci. Strong linkage disequilibrium, not associated with geographical distance, and 2 ma in genetic clusters each considerably heterogeneous, was observed. These re sults support the hypotheses previously proposed that T. cruzi natural popu lations are composed of highly diversified genetic clones distributed into 2 main phylogenetic lineages: lineage 1, the most ubiquitous in the endemic area, was more frequently observed in sylvatic cycles, whereas lineage 2, predominant in humans and domestic cycles, in the southern part of the area surveyed, was further partitioned into 5 lesser genetic subdivisions. T. c ruzi appears therefore subdivided into at least 6 'discrete typing units' o r DTUs (Tibayrenc, 1998a-c). We have identified various specific isoenzyme markers ('tags'; Tibayrenc, op. cit.) suitable for the routine identificati on of these DTUs for epidemiological tracking purposes. We discuss the corr espondence with previous classifications and with the recent recommendation s of the 90th anniversary of the discovery of Chagas disease symposium, as well as the impact of T. cruzi genetic variability on this parasite's biome dical diversity.