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Chagas disease remains a public health concern in Brazil and other Latin American countries, mainly due to the potential domiciliation of native triatomine species. We analyzed the genetic variability of Triatoma pseudomaculata in sylvatic and peridomestic ecotopes throughout three localities in the northeastern state of Bahia, Brazil. We studied polymorphisms generated by random amplified polymorphic DNA (RAPD) and isoenzyme electrophoresis analyses. Based on RAPD analysis, each specimen was assigned to one of three genetic clusters. Although all sylvatic specimens from one locality were grouped into the same cluster, sylvatic and peridomestic specimens from the other two localities were broadly distributed between the remaining two clusters, suggesting that geographic population structuring was not occurring. Furthermore, isoenzyme analysis suggested that distinct populations were in Hardy-Weinberg equilibrium. Low statistical values for Wright's Fst index also supported the absence of population structuring and suggested the occurrence of panmixia. We conclude that genetic flow occurs between sylvatic and peridomestic T. pseudomaculata populations, probably as a consequence of passive and active dispersion of the insects, associated with deforestation and anthropic transformations. Journal of Vector Ecology 35 (2): 295-300. 2010.

BackgroundPanstrongylus lutzi (Neiva & Pinto, 1923) is a triatomine species native to Caatinga habitats in north-eastern Brazil. It is considered an important vector of Chagas disease in this region, presenting high rates of natural infection with Trypanosoma cruzi Chagas, 1909, and readily invading houses by flight. This study describes a previously unknown chromosomal sex system in the genus Panstrongylus based on P. lutzi.MethodsFifth-instar and male adults of P. lutzi originating from municipality of Várzea Alegre, Ceará (Brazil) were analysed. Chromosomal analyses of male meiotic process were done by Giemsa staining.ResultsChromosomal analyses of male meiosis reveal a diploid chromosome number of 24 chromosomes (20 autosomes plus X1X2X3Y). During meiotic prophase I, the sex chromosomes remained close together, forming four heteropycnotic chromocenters in zygotene, and a single chromocenter in pachytene and diplotene. Still at the diplotene stage, each one of the ten autosomal bivalents showed an evident chiasma. In metaphase I, the four sex chromosomes appeared clearly separated. The three X chromosomes were the smallest of the complement and isopycnotic with respect to the Y chromosome. Two bivalents appear larger, whereas the other eight showed no significant difference in size.ConclusionKaryotype analysis of P. lutzi revealed a new sex system in the genus Panstrongylus. This result is of utmost importance to karyosystematics of P. lutzi, and demonstrates the need for further studies of this type in the subfamily Triatominae.

This survey aimed to assess the presence of triatomine vectors of Chagas disease within the rural communities of São João do Piauí, Northeast Brazil. Intradomiciliary and peridomiciliary collection strategies were implemented wherein 279 specimens of Triatoma brasiliensis macromelasoma, both nymph and adult were found in 15 (50%) of the studied homes. Of the intradomiciliary insects, 73 (67.6%) were identified as nymph instars (1st instar [N1]= 6, N2= 14, N3= 28, N4= 7 and N5= 18). In the studied communities, a continuous interaction between triatomine bugs and humans could be shown. It is therefore urgent that suitable strategies for the control of the triatomine vector are implemented in this area.