Análise de relacionamento genético entre populações de Aedes aegypti de diferentes regiões geográficas do Estado de São Paulo, Brasil

Marcadores de RAPD são utilizados para a análise de diferenciação genética de Aedes aegypti, pois permitem o estudo do relacionamento genético entre populações. Este estudo procurou identificar populações em diferentes regiões geográficas do Estado de São Paulo visando entender o padrão de infestação do A. aegypti. O dendrograma construído com os dados combinados dos padrões de RAPD mostrou que os mosquitos foram separados em dois grupos principais. Mosquitos da região oeste do Estado de São Paulo constituíram um grupo e o outro grupo foi composto de mosquitos de uma cepa de laboratório juntamente com mosquitos de uma cidade litorânea onde se localiza o maior porto da América Latina. Estes dados concordam com o relato de infestação do Estado de São Paulo. A proximidade genética foi maior entre mosquitos cuja origem geográfica foi mais próxima, entretanto, mosquitos da cidade litorânea foram geneticamente mais próximos aos mosquitos criados em laboratório que àqueles coletados no Estado de São Paulo. A origem da infestação deste local permanece obscura mas certamente está relacionada a mosquitos de origens diferentes daqueles que infestaram a região oeste e norte do Estado na década de 80.RAPD markers have been used for the analysis of genetic differentiation of Aedes aegypti, because they allow the study of genetic relationships among populations. The aim of this study was to identify populations in different geographic regions of the São Paulo State in order to understand the infestation pattern of A. aegypti. The dendrogram constructed with the combined data set of the RAPD patterns showed that the mosquitoes were segregated into two major clusters. Mosquitoes from the Western region of the São Paulo State constituted one cluster and the other was composed of mosquitoes from a laboratory strain and from a coastal city, where the largest Latin American port is located. These data are in agreement with the report on the infestation in the São Paulo State. The genetic proximity was greater between mosquitoes whose geographic origin was closer. However, mosquitoes from the coastal city were genetically closer to laboratory-reared mosquitoes than to field-collected mosquitoes from the São Paulo State. The origin of the infestation in this place remains unclear, but certainly it is related to mosquitoes of origins different from those that infested the West and North region of the State in the 80's

Efeito residual de temephós em larvas de Aedes aegypti

Uma das estratégias de controle do Aedes aegypti é o uso do larvicida temephós, cujo efeito residual prolongado permite a programação de tratamentos focais. O objetivo deste estudo é verificar a duração do efeito residual do temephós simulando-se uma situação de campo. Recipientes plásticos com capacidade de um e cinco litros, foram tratados com temephós e seu efeito residual testado a cada trinta dias. Foram observadas diferentes durações do efeito residual, o qual foi maior nos recipientes localizados no interior do laboratório comparados aos expostos fora do laboratório. Nos recipientes de um litro o efeito residual foi superior ao de cinco litros. O pH e a salinidade da água, durante o período de estudo, não interferiram com o efeito do larvicida.<br>One of the most used strategies for controlling Aedes aegypti is the use of the larvicide temephos (Abate). This larvicide has a prolonged residual effect which allows planning the focal treatments. This study aims to verify the duration of the laivicide residual effect simulating a field situation. Plastic containers of one arid five liters were treated with temephos and the residual effect was evaluated every 30 day after the treatment. Different residual effect was observed in the containers placed outside attd inside the laboratory. The containers of one liter showed a longer residual effect than the five liters containers. The water salinity as well as the pH, during the test did not affect the larvicide effect

Follow Up Estimation Of Aedes Aegypti Entomological Parameters And Mathematical Modellings.

The dengue virus is a vector-borne disease transmitted by mosquito Aedes aegypti and the incidence is strongly influenced by temperature and humidity which vary seasonally. To assess the effects of temperature on dengue transmission, mathematical models are developed based on the population dynamics theory. However, depending on the hypotheses of the modelling, different outcomes regarding to the risk of epidemics are obtained. We address this question comparing two simple models supplied with model's parameters estimated from temperature-controlled experiments, especially the entomological parameters regarded to the mosquito's life cycle in different temperatures. Once obtained the mortality and transition rates of different stages comprising the life cycle of mosquito and the oviposition rate, we compare the capacity of vector reproduction (the basic offspring number) and the risk of infection (basic reproduction number) provided by two models. The extended model, which is more realistic, showed that both mosquito population and dengue risk are situated at higher values than the simplified model, even that the basic offspring number is lower.103360-7

Impact of insecticide resistance on the field control of Aedes aegypti in the State of São Paulo

Introduction The need to control dengue transmission by means of insecticides has led to the development of resistance to most of the products used worldwide against mosquitoes. In the State of São Paulo, the Superintendência de Controle de Endemias (SUCEN) has annually monitored the susceptibility of Aedes aegypti to insecticides since 1996; since 1999, surveys were conducted in collaboration with the National Network of Laboratories (MoReNAa Network) and were coordinated by the Ministry of Health. In this study, in addition to the biological characterization of insecticide resistance in the laboratory, the impact of resistance on field control was evaluated for vector populations that showed resistance in laboratory assays. Methods Field efficacy tests with larvicides and adulticides were performed over a 13-year period, using World Health Organization protocols. Results Data from the field tests showed a reduction in the residual effect of temephos on populations with a resistance ratio of 3. For adults, field control was less effective in populations characterized as resistant in laboratory qualitative assays, and this was confirmed using qualitative assays and field evaluation. Conclusions Our results indicated that management of resistance development needs to be adopted when insect populations show reduced susceptibility. The use of insecticides is a self-limiting tool that needs to be applied cautiously, and dengue control requires more sustainable strategies.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Standardization of bioassays for monitoring resistance to insecticides in Aedes aegypti

Since the reintroduction of Aedes aegypti in Brazil in the 1980s, insecticide use for its control is routine. The chemical control efficacy is threatened by vectors developing resistance to insecticides. The World Health Organization, recognizing the impact of insecticide resistance in vector control programmes, proposed standardizing bioassays for detecting and monitoring resistance using a diagnostic dose method. As Brazil has a national programme for monitoring the resistance of Ae. aegypti populations to insecticides, this study was designed to compare diagnostic bioassays at WHO suggested concentrations and those estimated for local conditions. Populations were resistant to both temephos doses. But important differences were seen for fenitrothion and malathion, which could lead to under- or over-estimation of resistance respectively. These results and inclusion of a diagnostic dose bioassay standard for larvae are discussed

Possible genotypes for Latin American <i>Aedes aegypti</i> populations, considering the single nucleotide polymorphisms in the 1016 and 1534 Na_V sites.

<p>Possible genotypes for Latin American <i>Aedes aegypti</i> populations, considering the single nucleotide polymorphisms in the 1016 and 1534 Na_V sites.</p

Pyrethroid resistance persists after ten years without usage against <i>Aedes aegypti</i> in governmental campaigns: Lessons from São Paulo State, Brazil

<div><p>Background</p><p><i>Aedes aegypti</i>, vector of dengue, chikungunya and Zika viruses, is found at high densities in tropical urban areas. The dissemination of this vector is partially the consequence of failures in current vector control methods, still mainly relying upon insecticides. In the State of São Paulo (SP), Brazil, public health managers employed pyrethroids against <i>Ae</i>. <i>aegypti</i> adults from 1989 to 2000, when a robust insecticide resistance monitoring system detected resistance to pyrethroids in several <i>Ae</i>. <i>aegypti</i> populations. However, pyrethroids are also the preferred compounds engaged in household applications due to their rapid <i>knockdown</i> effect, lower toxicity to mammals and less irritating smell.</p><p>Methodology/Principal findings</p><p>We evaluated pyrethroid resistance in <i>Ae</i>. <i>aegypti</i> populations over the course of a decade, from 2004 to 2015, after interruption of pyrethroid public applications in SP. Qualitative bioassays with papers impregnated with a deltamethrin diagnostic dose (DD) performed with insects from seven SP municipalities and evaluated yearly from 2006 to 2014, detected resistance in most of the cases. Quantitative bioassays were also carried out with four populations in 2011, suggesting a positive correlation between resistance level and survivorship in the DD bioassays. Biochemical tests conducted with seven insect populations in 2006 and 2015, detected increasing metabolic alterations of all major classes of detoxifying enzymes, mostly of mixed function oxidases. Genotyping of the voltage-gated sodium channel (<i>AaNa</i>_<i>V</i>, the pyrethroid target-site) with a TaqMan real time PCR based technique was performed from 2004 to 2014 in all seven localities. The two <i>kdr</i> mutations, Val1016Ile and Phe1534Cys, known to be spread throughout Brazil, were always present with a severe decrease of the susceptible allele over time.</p><p>Conclusions/Significance</p><p>These results are discussed in the context of public and domestic insecticide use, the necessity of implementation of a strong integrated vector control strategy and the conceptual misunderstanding between 'vector control' and 'chemical control of vectors'.</p></div

Qualitative (DD) deltamethrin bioassays with F1 or F2 <i>Aedes aegypti</i> female adults derived from São Paulo State populations collected from 2006 to 2014.

<p>Qualitative (DD) deltamethrin bioassays with F1 or F2 <i>Aedes aegypti</i> female adults derived from São Paulo State populations collected from 2006 to 2014.</p

Frequencies of susceptible (Na_VS) or <i>kdr</i> (Na_VR1 and Na_VR2) alleles and resistance genotypes (R1R1, R1/R2 and R2R2) in <i>Aedes aegypti</i> populations from São Paulo State (SP) between 2003 and 2014.

<p>The composition of each allele considered both 1016 and 1534 Na_V sites for each genotyped individual: Na_VS (1016 Val⁺ + 1534 Phe⁺), Na_VR1 (1016 Val⁺ + 1534 Cys^<i>kdr</i>) and Na_VR2 (1016 Ile^<i>kdr</i> + 1534 Cys^<i>kdr</i>). The municipalities are placed inside the highlighted map of SP State.</p