Oviposition of Aedes aegypti Linnaeus, 1762 and Aedes albopictus Skuse, 1894 (Diptera: Culicidae) under laboratory and field conditions using ovitraps associated to different control agents, Manaus, Amazonas, Brazil

ABSTRACT The aim of this study was to analyze the effectiveness of different control agents of Aedes aegypti and Aedes albopictus associated with ovitraps under laboratory and field conditions. Five treatments were used: grass infusion + Bacillus thuringiensis israelensis (gI + Bti), grass infusion + Saccharopolyspora spinosa (gI + Ss), grass infusion + Pyriproxyfen (gI + P), distilled water + Toxorhynchites haemorrhoidalis (dW + Th), and grass infusion (gI) (control). The highest mean number of eggs of both species were obtained with grass infusion in the laboratory. Among control agents, the lowest mean of A. aegypti eggs occurred with gI + Ss and the lowest mean of A. albopictus eggs occurred with dW + Th. There was no difference between treatments in A. aegypti (P = 0.4320) and A. albopictus (P = 0.7179). In the field, the highest mean number of eggs for both species were obtained with gI + Ss, and the lowest values were obtained with gI + P (P = 0.0124). The treatments can be applied to both the surveillance and the control, but ovitraps with biological larvicide Bti were more effective and safer considering the number of eggs laid and selectivity of pathogens for mosquitoes.

Isolation and molecular characterization of Bacillus thuringiensis found in soils of the Cerrado region of Brazil, and their toxicity to Aedes aegypti larvae

ABSTRACT This study investigated the potential of Bacillus thuringiensis isolates obtained in the Cerrado region of the Brazilian state of Maranhão for the biological control of Aedes aegypti larvae. The isolates were obtained from soil samples and the identification of the B. thuringiensis colonies was based on morphological characteristics. Bioassays were run to assess the pathogenicity and toxicity of the different strains of the B. thuringiensis against third-instar larvae of A. aegypti. Protein profiles were obtained by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Polymerase chain reaction assays were used to detect the toxin genes found in the bacterial isolates. Overall, 12 (4.0%) of the 300 isolates obtained from 45 soil samples were found to present larvicidal activity, with the BtMA-104, BtMA-401 and BtMA-560 isolates causing 100% of mortality. The BtMA-401 isolate was the most virulent, with the lowest median lethal concentration (LC50) (0.004 × 107 spores/mL), followed by the Bacillus thuringiensis var. israelensis standard (0.32 × 107 spores/mL). The protein profiles of BtMA-25 and BtMA-401 isolates indicated the presence of molecular mass consistent with the presence of the proteins Cry4Aa, Cry11Aa and Cyt1, similar to the profile of Bacillus thuringiensis var. israelensis IPS-82. Surprisingly, however, none of the cry and cyt genes analyzed were amplified in the isolate BtMA-401. The results of the present study revealed the larvicidal potential of B. thuringiensis isolates found in the soils of the Cerrado region from Maranhão, although further research will be necessary to better elucidate and describe other genes associated with the production of insecticidal toxins in these isolates.

Isolation of Bacillus thuringiensis from the state of Amazonas, in Brazil, and screening against Aedes aegypti (Diptera, Culicidae)

We investigated the use of Bacillus thuringiensis isolated in the state of Amazonas, in Brazil, for the biological control of the dengue vector Aedes aegypti. From 25 soil samples collected in nine municipalities, 484 bacterial colonies were obtained, 57 (11.78%) of which were identified as B. thuringiensis. Six isolates, IBt-03, IBt-06, IBt-07, IBt-28, IBt-30, and BtAM-27 showed insecticidal activity, and only BtAM-27 presents the five genes investigated cry4Aa, cry4Ba, cry10Aa, cry11Aa, and cry11Ba. The IBt-07 and IBt- 28, with lower LC50 values, showed equal toxicity compared to the standards. The isolates of B. thuringiensis from Amazonas constitute potential new means of biological control for A. aegypti, because of their larvicidal activity and the possibility that they may also contain new combinations of toxins.

Influence of abiotic factors on the effectiveness of Bacillus thuringiensis israelensis (Berliner, 1911) against larvae of Aedes aegypti (Linnaeus, 1762) / Influencia de los factores abióticos en la efectividad de la Bacillus thuringiensis israelensis (Berliner, 1911) contra larvas de Aedes aegypti (Linnaeus, 1762)

Introduction: Bacillus thuringiensis , has been used worldwide for the control of mosquitoes, particularly in combating Aedes aegypti. Various formulations have been made however, the effectiveness of these insecticides vary varies considerably according to the environmental conditions. Objective: to evaluate the influence of abiotic factors on the effectiveness of B. thuringiensis var. israelensis to against larvae of Ae. aegypti. Methods: we conducted bioassay experiments in the campus of the CESC / UEMA. With use of 20 Twenty cement tanks, of these, were used, 10 of which were exposed to environmental factors, and only. Of these, 5 were treated and 5 served as controls. The other 10 tanks were placed in the shade, also again 5 were treated and 5 untreated were not (control). After treatment, the 25 stage L 3 larvae were placed in 25 L 3 each stage tank and mortality. Mortality readings were taken after 24 hours and every 7 days. Weekly water samples were collected from all tanks to measure once a week to check the number of viable spores and evaluate bacterial recycling. Results and discussion: the larvicidal efficacy: The larvicide showed initial efficacy, killing 100 percent of the larvae in tanks that were located both in the sun and in the shade. Environmental factors, sunlight, temperature and rainfall negatively affected the effectiveness of the product, because for there was a reduction in the effectiveness of the product throughout the experiment. It was observed variation in the number of spores during the development of the experiment demonstrating, showing that the bacterium has potential recyclability. Conclusion: these data serve as parameters for improving to in Bti-based insecticides, in order to make the with a view to making formulations more suited toin keeping with the environmental conditions of our region(AU)

Introducción: la Bacillus thuringiensis se ha utilizado en muchas regiones del mundo para el control de los mosquitos, sobre todo en el combate contra el Aedes aegypti. Se han elaborado varias formulaciones; sin embargo, la efectividad de esos insecticidas varía considerablemente según las condiciones ambientales. Objetivo: evaluar la influencia de los factores abióticos en la efectividad de la B. thuringiensis var. israelensis contra larvas de Ae. aegypti. Métodos: se realizaron bioensayos experimentales en el campus de la CESC / UEMA. Se utilizaron 20 tanques de cemento, 10 de los cuales quedaron expuestos a factores ambientales. De ellos, 5 fueron tratados y 5 sirvieron como controles. Los otros 10 tanques fueron ubicados en la sombra, y también en este caso 5 fueron tratados y 5 no (controles). Después del tratamiento, se colocaron 25 larvas en estadio larval L3 en cada tanque. Se realizaron lecturas de mortalidad luego de 24 horas y cada 7 días. Se tomaron muestras de agua de todos los tanques una vez a la semana para comprobar el número de esporas viables y evaluar el reciclaje bacteriano. Resultados y discusión: el larvicida mostró eficacia inicial, matando el 100 por ciento de las larvas de tanques ubicados tanto al sol como en la sombra. Los factores ambientales, la luz solar, la temperatura y la lluvia afectaron negativamente la efectividad del producto, constatándose una reducción de la misma a lo largo del experimento. Se observaron variaciones en el número de esporas durante el experimento, lo que demuestra que la bacteria presenta potencial de reciclaje. Conclusión: los datos obtenidos sirven de parámetros para el mejoramiento de los insecticidas a base de Bti, con vistas a elaborar formulaciones más acordes con las condiciones ambientales de nuestra región(AU)

Variation in Aedes aegypti (Linnaeus) (Diptera, Culicidae) infestation in artificial containers in Caxias, state of Maranhão, Brazil / Variação da infestação de Aedes aegypti (Linnaeus), (Diptera, Culicidae) em recipientes artificiais em Caxias, estado do Maranhão, Brasil

INTRODUCTION: Dengue is a serious public health problem worldwide, with cases reported annually in tropical and subtropical regions. Aedes aegypti (Linnaeus, 1762), the main vector of dengue, is a domiciliary species with high dispersal and survival capacities and can use various artificial containers as breeding sites. We assessed potential container breeding sites of A. aegypti in the municipality of Caxias, Maranhão, Brazil. METHODS: In the initial phase, we analyzed 900 properties in 3 neighborhoods during the dry and rainy seasons (August-October 2005 and February-April 2006, respectively). During the second sampling period, September 2006-August 2007, we used 5 assessment cycles for 300 properties in a single neighborhood. RESULTS: During the dry and rainy seasons, water-storage containers comprised 55.7% (n = 1,970) and 48.5% (n = 1,836) of the total containers inspected, and showed the highest productivity of immature A. aegypti; we found 23.7 and 106.1 individuals/container, respectively, in peridomicile sites. In intradomicile sites, water-storage containers were also the most important breeding sites with 86.4% (n = 973) and 85.6% (n = 900) of all containers and a mean of 7.9 and 108.3 individuals/container in the dry and rainy seaso-October 2006 (1,342). The highest number of positives (70) was recorded in May, mostly (94%) in storage containers. CONCLUSIONS: Storage containers are the principal and most productive A. aegypti breeding sites and are a major contributing factor to the maintenance of this vector in Caxias.

INTRODUÇÃO: A dengue constitui de um sério problema de saúde pública mundial, com casos sendo registrados anualmente nas regiões tropicais e subtropicais. O Aedes aegypti(Linnaeus, 1762) é o principal vetor da doença, um mosquito domiciliado de fácil dispersão e sobrevivência, com capacidade de utilizar variados recipientes artificiais como criadouro. Em vista disso, neste trabalho investigou-se os tipos de recipientes potenciais criadouros de A. aegypti na Cidade de Caxias, Maranhão, Brasil. MÉTODOS: Inicialmente, a pesquisa foi desenvolvida em três bairros e 900 imóveis analisados no período da seca e das chuvas (agosto a outubro de 2005 e fevereiro a abril de 2006, respectivamente). Um segundo período de amostragem ocorreu de setembro de 2006 a agosto de 2007 em que inspeções de cinco ciclos foram desenvolvidas em um dos bairros com 300 imóveis amostrados. RESULTADOS: Os recipientes de armazenamento de água representaram 55,7% (n=1.970) e 48,5% (n=1.836) do total dos inspecionados, e maior produtividade de imaturos de A. aegypti, com proporção de 23,7 e 106,1 por recipiente no peridomicílio, nas estações seca e chuvosa respectivamente. No intradomicílio, também foi mais representativo, 86,4% (n=973) e 84,6% (n=900), apresentando média de 7,9 e 108,3 indivíduos, nas duas estações. O maior número de recipientes com água foi registrado em setembro e outubro 2006 (1.342), obtendo-se maior número de positivos (70) no mês de maio, sendo (94%) pertencentes ao grupo armazenamento. CONCLUSÕES: Armazenamento são os principais criadouros de A. aegypti, contribuindo na manutenção do vetor na cidade de Caxias, Maranhão.