Geographical structuring ofTrypanosoma cruzipopulations from ChileanTriatoma infestanstriatomines and their genetic relationship with other Latino American counterparts

Abstract

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.

Differential Pattern of Infection of Sylvatic Nymphs and Domiciliary Adults of Triatoma infestans with Trypanosoma cruzi Genotypes in Chile

“…12 Recent studies using three microsatellites for T. cruzi genotyping reported that from 12 T. infestans found in houses in the Metropolitan Region that were tested, five had TcI, five had TcIII, and two had hybrid lineages. 18 In this study, using the four probes described, we found no unknown lineages. Thus, it is unlikely that there is a genotype that has not been detected.…”

“…17 More recently, the presence of TcIII was documented in Triatoma infestans from Chile by using three microsatellite markers, with TcI, a hybrid (TcV + TcVI), and unknown lineages. 18 Chagas disease is endemic to Chile. Three sylvatic triatomine species have been described: the kissing bugs M. spinolai Porter 1934, M. gajardoi Frias, Henry and Gonzalez 1998, and M. parapatrica.…”

Microsatellite loci-based distribution of Trypanosoma cruzi genotypes from Chilean chronic Chagas disease patients and Triatoma infestans is concordant with a specific host-parasite association hypothesis

“…Thus, if the predominant clone was homozygous and the sample had three additional alleles (a total of four alleles), it was concluded that the minimum number of clones (MNC) is 3, because an odd number of alleles was considered as another clone. By contrast, in the same sample if the predominant clone was heterozygous, it was concluded that the MNC is 2, as described (Venegas et al 2011).…”

“…The determination of the genotype of the predominant T. cruzi clone in samples containing multiple alleles per locus was conducted taking into account the distance and the height in FU of the two highest peaks, the major and secondary peaks directly in the electropherogram, as described (Venegas et al 2011).…”

“…This was conducted by the Fisher method across the loci SCLE10, SCLE11 and MCLE01, described previously (Oliveira et al 1998;De Freitas et al 2006;Venegas et al 2011). The genotypic differentiation was analysed with the Genepop program using the Markov algorithm (Raymond and Rousset 1995a;1995b).…”