Trypanosoma cruzi diversity in infected dogs from areas of the north coast of Chile

As part of a multi-site research program on the eco-epidemiology and control of Chagas disease in northern Chile, we sought to identify the Trypanosoma cruzi discrete typing units (DTUs) infecting rural and peridomestic dogs, using direct methods without grown of the parasite in the laboratory and thus to assess the use of this species as a sentinel of the disease in well-defined endemic areas of T. cruzi in Chile. Infected dogs (35) from three villages were included in the study. The studied villages were Caleta Río Seco and Caleta San Marcos, both in the Tarapacá Region, and La Serena in the Coquimbo Region. These villages were selected based on previous evidence of Mepraia infection reports of the Chilean Ministry of Health. Amplicons from nested-PCR positive samples were used as targets to determine the infective T. cruzi DTUs circulating in blood using PCR-DNA blotting and hybridization assays with five specific DNA probes (TcI, TcII, TcIII, TcV and TcVI). Results of hybridization with dog samples from Caleta Rio Seco showed single infections in 2 out of 16 and mixed infections in 14 out of 16. TcVI was the most frequent DTU found in this area. A highlight is that for the first time the presence of TcIII is reported in this area. Samples from Caleta San Marcos showed single infections in 5 out of 9 and mixed infections in 4 out of 9. TcVI was the most frequent DTU found in this area. Samples from La Serena showed single infections in 5 out of 10 and mixed infections in 2 out of 10; we were unable to genotype the other 3 samples. Our results indicate that infection by T. cruzi DTUs in dogs is not homogeneously distributed but rather specific to each region of our country, as demonstrated by the differences in the T. cruzi DTU distribution in some localities.