Entoepidemiology of Chagas disease in the Western region of the State of São Paulo from 2004 to 2008, and cytogenetic analysis in Rhodnius neglectus (Hemiptera, Triatominae).

To complement the epidemiological data and assist in the prophylaxis of Chagas disease in the State of São Paulo, we examined entomological lifting conducted in 40 municipalities of the Western region of the state from 2004 to 2008, highlighted the main vector species in this region, and reanalyzed the cytogenetic characteristics of Rhodnius neglectus from 3 different Brazilian states (Formoso/GO, Frutal/MG, Guaíra/SP, and Pitangueiras/SP). The municipalities of Castilho and Santo Antônio do Acaranguá registered the highest relative amounts of notifications. The main species notified in Western São Paulo were Triatoma sordida and R. neglectus. We collected a large number of T. sordida in 2005 and noted the absence of notification of infected insects in 2008. We observed no variation in chromosomal characteristics of R. neglectus of different states. These data are complementary to the survey presented from 1990 to 1999, as the vector species were the same (T. sordida and R. neglectus), with emphasis on T. sordida. We corroborate the future colonization domiciliary initially proposed for T. sordida in the region and underscore the importance of vector control programs in the prophylaxis of Chagas disease. Furthermore, we observed that the populations of R. neglectus in Brazil showed no intraspecific variation and we corroborated the chromosomal patterns originally described. These data are important for understanding the evolution of these hematophagous insects, which are vectors of Chagas disease.

Genetic structure of Aedes aegypti populations determined using pairwise comparisons.

The biological characteristics of Aedes aegypti (Diptera, Culicidae), which is a vector of dengue and yellow fever, make this organism a good model for studying population structure and the events that may influence it under the effect of human activity. We assessed the genetic variability of five A. aegypti populations using RAPD-PCR technique and six primers. Four populations were from Brazil and one was from the USA. A total of 165 polymorphic DNA loci were generated. Considering the six primers and the five populations, the mean value of inter-population genetic diversity (Gst) was 0.277, which is considered high according to the Wright classification. However, pairwise comparisons of the populations gave variable Gst values ranging from 0.044 to 0.289. This variation followed the population's geographic distance to some extent but was also influenced by human activity. The lowest Gst values were obtained in the comparison of populations from cities with intensive commercial and medical contacts. These mosquito populations were previously classified as insecticide resistant, susceptible, or with decreased susceptibility; this parameter apparently had an effect on the Gst values obtained in the pairwise comparisons.