**4. Genetic diversity**

Initially it was thought that *T. cruzi* was a highly clonal species that had experienced little genetic mixing during its evolution [27]. However, due to increasingly detailed studies of the structure of populations and nuclear and mitochondrial DNA of *T. cruzi,* it has been suggested that in addition to clonal propagation, there have been more recent and frequent hybridizations and genetic exchange than previously thought [28]. At present, there are six discrete typification units (DTU TcI-VI) accepted by international consensus [29] that include at least two hybrid lineages (TcV and TcVI) and an additional one mainly found in bats (TcBat) [30, 31], closely related to TcI. Among these DTUs, TcI is the most diverse and widely distributed lineage with the smallest genome, the least amount of aneuploidy, and probably

related with some hybrid lineages [28]. The association of a particular *T. cruzi* strain with the diverse spectrum of the disease has not been completely established [32], although it has been possible to show some correlations. For example, Chagas disease megasyndrome is mainly found in South America where TcV and TcVI predominate. On the other hand, in North and Central America, cardiomyopathy is more common with Tc1 being strongly associated with human infection [33].
