Discussion

Despite the existence of two recent natural hybrid lineages (TcV and TcVI), which are sympatric with severe disease in southern endemic areas, the principal reproductive strategy of Trypanosoma cruzi, the aetiological agent of Chagas disease, remains controversial. High resolution nuclear and mitochondrial genotyping of potential hybrid isolates from Colombia was undertaken to resolve their putative status as novel recombinants. All suspected Colombian hybrids were highly heterozygous, minimally diverse and possessed intact parental alleles at each loci. Compared to local strains, Colombian hybrids were distinct from, but more closely related to, southern TcVI isolates. Based on independent inheritance patterns of microsatellite loci, our data support the hypothesis that two recombination events led to the formation of TcV and TcVI. However, more private alleles among Colombian hybrids and the sharing of their mitochondrial haplotypes with southern samples, suggests they are unlikely to be predecessors of southern TcVI strains, but were also not clear descendants, and may instead represent a sibling group, which diverged and anthroponotically dispersed northwards. We discuss the important implications the geographical range expansion of TcVI has for emergent human Chagas disease in Colombia, considering the successful, epidemic establishment of this low-diversity genotype among domestic vectors and human infections in the South.