Genetic diversity of Trypanosoma cruzi isolates from triatomine bugs in the semi-arid region of Piauí State, northeastern Brazil.

The occurrence of triatomine species and the genetic diversity of Trypanosoma cruzi were investigated in anthropogenic environments in rural areas of nine municipalities in the Campo Maior, Picos, and Alto Médio Canindé microregions, Caatinga biome, Piauí State, in northeastern Brazil. Triatomines were identified and examined for T. cruzi infection by direct microscopic examination, xenoculture, and PCR-based methods. Parasite isolates obtained by xenoculture were molecularly characterized using mitochondrial and nuclear markers. A total of 661 triatomines were captured, predominantly Triatoma brasiliensis (92.1%, 603/661), followed by Triatoma pseudomaculata (7.3%, 48/661), Panstrongylus lutzi (1.0%, 7/661), and Rhodnius sp. (0.4%, 3/661). T. brasiliensis nymphs and adults were detected in intradomestic, peridomestic, and sylvatic environments, whereas T. pseudomaculata occurred exclusively in peridomestic areas. The overall natural infection rate by T. cruzi was 12.0% (67/556) based on direct examination, with T. brasiliensis accounting for most infected specimens. PCR confirmed all microscopically positive samples and detected additional infections among microscopy-negative specimens. Distinct T. cruzi discrete typing units (DTUs) were identified in different environments: DTU I was restricted to peridomestic areas; DTU II was widely distributed across intradomestic, peridomestic, and sylvatic environments; and DTU III, typically associated with the sylvatic cycle, was detected in both peridomestic and intradomestic settings. The association of T. brasiliensis with multiple domiciliary environments, and the spatial overlap of distinct DTUs, suggests its role as a key vector at the sylvatic-domestic interface, and suggests a complex and dynamic epidemiological scenario.