Urban infestation by Triatoma dimidiata in the city of Mérida, Yucatán, México.

The observation of widespread seasonal infestation by Triatoma dimidiata in rural villages around the city of Mérida, Yucatán, México, led us to reconsider the presence of Chagas disease vectors and the risk factors for house infestation in the city itself. Bugs were collected in 150 houses from 30 neighborhoods distributed throughout the city. We observed a widespread infestation by T. dimidiata in the city, with 38% of infested houses and 48% of the collected triatomines testing positive for Trypanosoma cruzi. House infestation by triatomines was greatest during the months of April-June. Infestation risk factors were related with backyard characteristics rather than housing type and quality of housing: houses located in the periphery of the city, with abandoned lots on the sides and large backyards, had a higher risk of being infested, while those with mosquito screens and occasional insecticide spraying in their yards had a lower risk. Several human blood meals were also identified and seropositive patients were distributed through most of the city, confirming the potential for urban transmission of Chagas disease to humans. This study shows that urban Chagas disease should not be neglected and surveillance programs should be implemented to further evaluate the magnitude of the problem.