Population genetic analyses were conducted using samples of Aedes aegypti from 14 localities in the north, southeast, northeast, and central regions of Brazil. An 852-bp region of the mitochondrial DNA cytochrome oxidase I (COI) gene was used in the analyses. Ten haplotypes were observed, and cluster analyses revealed 2 groups (lineages) separated by 8 fixed mutations, suggesting that the Brazilian Ae. aegypti populations probably came from East and West Africa, with evidence of multiple introductions, one related to Group 1 and two related to Group 2. Considering all samples, genetic and geographic distances were significantly correlated (r(2) = 0.332; P = 0.038), supporting the isolation by distance (IBD) model, but no correlation was detected for any particular region, which is consistent with human migrations and trade exchanges. Genetic distances (pairwise F(ST) and Nm values), AMOVA, and cluster analyses indicated a deep genetic structure for the Brazilian Ae. aegypti, probably resulting from several factors: multiple introductions associated with distinct lineages, geographic differentiation (IBD), passive dispersal patterns, control activities, extinction and recolonization events, and genetic drift.

Following reports of two autochthonous cases of sylvatic yellow fever in the State of São Paulo, Brazil, in 2000, entomological surveys were conducted with the objective of verifying the occurrence of vector species in forest environments close to or associated with riparian areas located in the western and northwestern regions of the State. Culicidae were captured in 39 sites distributed in four regions. Haemagogus leucocelaenus and Aedes albopictus were the most abundant species and were captured in all the regions studied. H. leucocelaenus was the most abundant species in the municipalities of Santa Albertina and Ouroeste, where the two cases of sylvatic yellow fever had been reported. Mosquitoes from the janthinomys/capricornii group were only found at eight sites in the São José do Rio Preto region, while Sabethes chloropterus was found at one site in Ribeirão Preto. H. leucocelaenus showed its capacity to adapt to a secondary and degraded environment. Our results indicate a wide receptive area for yellow fever transmission in the State of São Paulo, with particular emphasis on the possibility of H. leucocelaenus being involved in the maintenance of this sylvatic focus of the disease.

-In 2000, an outbreak of sylvatic yellow fever possibly occurred in gallery forests of the Grande river in the Paraná basin in the northwestern region of São Paulo state. The aim of this study was to obtain information on the bionomics of Haemagogus and other mosquitoes inside tree holes in that area. Eighteen open tree holes were sampled for immature specimens. Adults were collected twice a month in the forest in Santa Albertina county from July 2000 to June 2001. The seasonal frequency of fourth instars was obtained by the Williams geometric mean (Mw), while the adult frequency was estimated either by hourly arithmetic or the Williams' means. Cole's index was applied to evaluate larval inter-specifi c associations. Among the ten mosquito species identifi ed, the most abundant was Aedes terrens Walker followed by Sabethes tridentatus Cerqueira and Haemagogus janthinomys Dyar. Larval and adult abundance of these species was higher in summer than in winter. Although larval abundance of Hg. janthinomys peaked in the rainy season, correlation with rainfall was not signifi cant. Six groups of larval associations were distinguished, one of which the most positively stable. The Hg. janthinomys and Ae. terrens association was signifi cant, and Limatus durhamii Theobald was the species with most negative associations.

SUMMARYDiversity of mosquito species was evaluated in different habitats before and after the Igarapava reservoir flooding in the Grande River, Southern Cerrado of Brazil. We aimed at verifying changes in these mosquito populations in consequence of the lake formation. Four habitats were selected as sampling stations: peridomiciliary habitat, pasture, "veredas" and gallery forest patch. Bimonthly collections were made with the Shannon trap and human bait, including diurnal, crepuscular and nocturnal period of mosquito activity. The Shannon Index results from the potential vectors were compared using Student t-test. Aedes scapularis, Anopheles darlingi and An. albitarsis senso latu seasonal abundance were described with moving average and compared using χ 2 test. There were changes in the mosquito frequency in the habitats, except for the "veredas" that was 13 km away from the catchment area. The altering in mosquito species seasonal abundance suggests breeding places expansion. Diversity indexes can be used to monitor changes in mosquito vector population in environments where abrupt disturbance can alter disease transmission cycles.

Avaliou-se o efeito da aplicação de inseticida sobre formas adultas de Aedes aegypti realizada a ultrabaixo volume (UBV) com atomizadores motorizados portáteis e acoplados a veículo. Os tratamentos com ambos os equipamentos foram realizados em São José do Rio Preto e Marília, estado de São Paulo, Brasil. A efetividade foi verificada pela exposição de fêmeas de Ae. aegypti em gaiolas-sentinela. O impacto das aplicações na população adulta do vetor foi avaliado por meio da coleta de adultos no intradomicílio e peridomicílio antes e após os tratamentos. Os resultados obtidos com cada equipamento foram semelhantes nas duas cidades. A mortalidade de fêmeas expostas em gaiolas-sentinela, no intradomicílio, atingiu percentual médio de 96,5% nas duas cidades nas áreas tratadas com equipamento portátil. Foi de 54,3% o percentual nas áreas tratadas com equipamento acoplado a veículo. Na avaliação de impacto sobre a população adulta, as coletas revelaram que o equipamento portátil causou redução média de 84,3% na positividade dos imóveis e 77,9% de diminuição no número de fêmeas por imóvel. Com equipamento acoplado a veículo, houve redução de 49,7% na positividade de imóveis para fêmeas de Ae. aegypti e de 44,6% no número de fêmeas por imóvel. Os resultados demonstraram impacto significativamente maior na população adulta com equipamento portátil e também maior mortalidade no intradomicílio, local de maior permanência das fêmeas do vetor. DESCRITORES: Aedes aegypti; controle de formas adultas; ultrabaixo volume (ubv); atomizador portátil; atomizador acoplado a veículo.