In Brazil, Aedes aegypti resistance to temephos, used since 1967, was detected in several municipalities in 2000. Organophosphates were substituted by pyrethroids against adults and, in some localities, by Bti against larvae. However, high temephos resistance ratios were still detected between 2001 and 2004. Field-simulated assays confirmed a low temephos residual effect. Acethylcholinesterase and Mixed Function Oxidase profiles were not altered. In contrast, higher Esterase activity, studied with three substrates, was found in all examined populations collected in 2001. From 2001 to 2004, a slight reduction in alpha-Esterase (EST) and beta-EST activity together with a gradual increase of p-nitrophenyl acetate (PNPA)-EST was noted. Gluthathione-S-transferase alteration was encountered only in the northeast region in 2001, spreading the entire country thereafter. In general, except for alpha-EST and beta-EST, only one enzyme class was altered in each mosquito specimen. Data are discussed in the context of historic application of insecticides in Brazil.

Chemical insecticides have been widely used in Brazil for several years. This exposes mosquito populations to an intense selection pressure for resistance to insecticides. In 1999, the Brazilian National Health Foundation started the first program designed to monitor the resistance of Aedes aegypti to insecticides. We analyzed populations from 10 municipalities (from 84 selected in Brazil) in the states of Rio de Janeiro and Espírito Santo. Exposure of larvae to a diagnostic dose of temephos showed in alterations in susceptibility in all populations. Mosquitoes from eight municipalities exhibited resistance, with mortality levels ranging from 74% (Campos dos Goytacazes, Rio de Janeiro) to 23.5% (São Gonçalo, Rio de Janeiro). The resistance ratios of mosquitoes from three municipalities ranged from 3.59 to 12.41. Adults from only one municipality (Nova Iguaçu, Rio de Janeiro) remained susceptible to both fenitrothion and malathion. These results are being used to define new local vector control strategies.

No Brasil, o Aedes aegypti é responsável pela transmissão de dengue e o Aedes albopictus, potencial vetor, está se disseminando no país. O uso de inseticidas químicos ainda é o principal componente de controle do vetor. A ação das principais classes dos compostos tradicionalmente usados em Saúde Pública é descrita, assim como os mecanismos de resistência selecionados pelas populações do vetor. Produtos alternativos, com potencial de utilização no controle do A. aegypti, incluindo o biolarvicida Bti e alguns reguladores do desenvolvimento de insetos, também são discutidos. Pretende-se contribuir com o uso racional de inseticidas, considerando os diferentes componentes do controle integrado.

IntroductionThe mosquito Aedes aegypti, vector of dengue, chikungunya and yellow fever viruses, is an important target of vector control programs in tropical countries. Most mosquito surveillance programs are still based on the traditional household larval surveys, despite the availability of new trapping devices. We report the results of a multicentric entomological survey using four types of traps, besides the larval survey, to compare the entomological indices generated by these different surveillance tools in terms of their sensitivity to detect mosquito density variation.MethodsThe study was conducted in five mid-sized cities, representing variations of tropical climate regimens. Surveillance schemes using traps for adults (BG-Sentinel, Adultrap and MosquiTRAP) or eggs (ovitraps) were applied monthly to three 1 km2 areas per city. Simultaneously, larval surveys were performed. Trap positivity and density indices in each area were calculated and regressed against meteorological variables to characterize the seasonal pattern of mosquito infestation in all cities, as measured by each of the four traps.ResultsThe House Index was consistently low in most cities, with median always 0. Traps rarely produced null indices, pointing to their greater sensitivity in detecting the presence of Ae. aegypti in comparison to the larval survey. Trap positivity indices tend to plateau at high mosquito densities. Despite this, both indices, positivity and density, agreed on the seasonality of mosquito abundance in all cities. Mosquito seasonality associated preferentially with temperature than with precipitation even in areas where temperature variation is small.ConclusionsAll investigated traps performed better than the House Index in measuring the seasonal variation in mosquito abundance and should be considered as complements or alternatives to larval surveys. Choice between traps should further consider differences of cost and ease-of-use.