RESUMO
Background: Insects of the subfamily triatominae are the biological vectors of Trypanosoma cruzi, the causal agent of Chagas disease. Aim: To search for wild colonies of triatomines in the Metropolitan Region of Chile. Material and Methods: Ad hoc traps were placed in two endemic zones of the Metropolitan Region of Chile, during 30 nights. The dejections of 16 T infestans and 43 M spinolai specimens were examined under the microscope, searching for live metacyclic trypomastigotes. A polymerase chain reaction (PCR) was performed in macerates of all insects looking for T cruzi DNA. Results: A total of 269 bugs were captured. Forty four were Triatoma infestans and 225 were Mepraia spinolai. They were not syntopic, since T infestans was restricted to a Southern zone (Calera de Tango) while M spinolai was only found in the Northern zone (Til-Til). Both species were found associated to terrestrial bromeliads (Puya sp) but M spinolai was also detected in stony grounds. Microscopic examination of dejections yielded a trypano-triatomine index of 56.3 and 32.6 for T infestans and M spinolai, respectively. PCR detected T cruzi DNA in 41 and 43 percent of T infestans and M spinolai specimens, respectively. Conclusions: The finding of T infestans in a wild habitat is noticeable. This is the first report of such phenomenon in Chile. The high infection rates with T cruzi, explains the maintenance of Chagas disease wild cycle in Chile.