Geographical structuring of Trypanosoma cruzi populations from Chilean Triatoma infestans triatomines and their genetic relationship with other Latino American counterparts.

In order to obtain more information about the population structure of Chilean Trypanosoma cruzi, and their genetic relationship with other Latino American counterparts, we performed the study of T. cruzi samples detected in the midgut content of Triatoma infestans insects from three endemic regions of Chile. The genetic characteristics of these samples were analysed using microsatellite markers and PCR conditions that allow the detection of predominant T. cruzi clones directly in triatomine midgut content. Population genetic analyses using the Fisher's exact method, analysis of molecular variance (AMOVA) and the determination of F(ST) showed that the northern T. cruzi population sample was genetically differentiated from the two southern population counterparts. Further analysis showed that the cause of this genetic differentiation was the asymmetrical distribution of TcIII T. cruzi predominant clones. Considering all triatomines from the three regions, the most frequent predominant lineages were TcIII (38%), followed by TcI (34%) and hybrid (8%). No TcII lineage was observed along the predominant T. cruzi clones. The best phylogenetic reconstruction using the shared allelic genetic distance was concordant with the population genetic analysis and tree topology previously described studying foreign samples. The correlation studies showed that the lineage TcIII from the III region was genetically differentiated from the other two, and this differentiation was correlated with geographical distance including Chilean and mainly Brazilian samples. It will be interesting to investigate whether this geographical structure may be related with different clinical manifestation of Chagas disease.