LB 13-125 - Multiclonal vertical transmission of Trypanosoma cruzi in natural reservoir populations

The protozoan parasite Trypanosoma cruzi is the etiological agent of Chagas disease, often described as the most burdensome anthropozoosis in the Western Hemisphere. Vectors and hosts of T. cruzi are widely distributed across the United States and have been found in habitats across the rural-urban gradient. To date, it remains unclear how T. cruzi is sustained in mammalian reservoirs inhabiting urban landscapes where there appears to be few if any triatomine vectors present. Vertical transmission may be a pathway for sustaining multiclonal infection of T. cruzi in urban reservoirs if hosts and vectors are disconnected. Multiclonal infection occurs when multiple discrete typing units (DTUs) of T. cruzi are present concurrently in an individual. However, vertical transmission has thus far only been demonstrated in lab settings and has focused on infection of a singular DTU. Thus, the goal of our study was to determine if vertical transmission may also occur in natural host populations and can result in multiclonal infection of offspring. We tested this hypothesis by utilizing an existing collection of T. cruzi positive rodents from New Orleans (LA, USA), which allowed comparisons of 66 embryos against 12 infected parous females of Norway rats, black rats and house mice. We first used a diagnostic PCR to determine prevalence of T. cruzi infection in mothers and offspring, followed by a genotyping PCR assay that would detect the presence of multiple DTUs. We found that 15 of the 66 embryos were positive for T. cruzi infection; at least 1 embryo from each study species was positive. Of the 15 embryos infected by T.cruzi, 6 exhibited evidence of multiclonal infection. These results indicate, for the first time, that vertical transmission is occurring in natural rodent populations and that multiple DTUs can pass from mother to offspring. These findings can be particularly important for urban reservoir populations, as vertical transmission may serve as mechanism for sustaining multiclonal infection in hosts over time when contact with vectors can be uncommon. Overall, our results provide a new understanding of the relationship between T.cruzi and its hosts in an urban landscape.