Insecticide susceptibility of Aedes albopictus and Ae. aegypti from Brazil and the Swiss-Italian border region

Aedes aegypti and Ae. albopictus are two highly invasive mosquito species, both vectors of several viruses, including dengue, chikungunya and Zika. While Ae. aegypti is the primary vector in the tropics and sub-tropics, Ae. albopictus is increasingly under the public health watch as it has been implicated in arbovirus-transmission in more temperate regions, including continental Europe. Vector control using insecticides is the pillar of most control programmes; hence development of insecticide resistance is of great concern. As part of a Brazilian-Swiss Joint Research Programme we set out to assess whether there are any signs of existing or incipient insecticide resistance primarily against the larvicide Bacillus thuringiensis svar. israelensis (Bti), but also against currently applied and potentially alternative insecticides in our areas, Recife (Brazil) and the Swiss-Italian border region.; Following World Health Organization guidelines, dose-response curves for a range of insecticides were established for both colonized and field caught Ae. aegypti and Ae. albopictus. The larvicides included Bti, two of its toxins, Cry11Aa and Cry4Ba, Lysinibacillus sphaericus, Vectomax CG®, a formulated combination of Bti and L. sphaericus, and diflubenzuron. In addition to the larvicides, the Swiss-Italian Ae. albopictus populations were also tested against five adulticides (bendiocarb, dichlorodiphenyltrichloroethane, malathion, permethrin and λ-cyhalothrin).; Showing a similar dose-response, all mosquito populations were fully susceptible to the larvicides tested and, in particular, to Bti which is currently used both in Brazil and Switzerland. In addition, there were no signs of incipient resistance against Bti as larvae were equally susceptible to the individual toxins, Cry11Aa and Cry4Ba. The field-caught Swiss-Italian populations were susceptible to the adulticides tested but DDT mortality rates showed signs of reduced susceptibility.; The insecticides currently used for mosquito control in Switzerland and Brazil are still effective against the target populations. The present study provides an important reference as relatively few insecticide susceptibility surveys have been carried out with Ae. albopictus

Desafios da técnica de obtenção de microesferas de Bacillus thuringiensis israelensis associado a óleo essencial de Croton rhamnifolioides/ Challenges of Bacillus thuringiensis israelensis Microsphere techniques associated with Croton rhamnifolioides essential oil

No intuito de combater o mosquito Aedes aegypti métodos de controle têm sido testados para substituir o uso de inseticidas químicos, que provocam degradação ambiental e uma alta resistência dos mosquitos frente a tais produtos. Assim, o uso de produtos naturais como óleos essenciais e biolarvicidas tem sido uma alternativa aos produtos químicos convencionais. No entanto, tais produtos apresentam limitações decorrentes da baixa solubilidade em água, alta volatilidade ou degradação por exposição à radiação solar. Para minimizar estas incompatibilidades, a técnica de microencapsulamento é adotada como proteção, evitando o efeito de exposição inadequada dos ingredientes ativos. A produção de microencapsulados tem diversas etapas e desafios a serem suplantados, o que se buscou apresentar neste trabalho. Microesferas de Bacillus thuringiensis israelensis (Bti) associadas ao óleo essencial de Croton rhamnifolioides foram preparadas através do método de coacervação simples por gotejamento da suspensão bioativa em alginato de sódio a 1% e 2% em meio com CaCl2. Os testes larvicidas com A. aegypti em estágio L3 foram realizados tanto no pó seco, resultado do biocultivo, como das microesferas formuladas com este ativo e o óleo essencial. A CL 50 e a CL 90 do pó seco foram de 0,12 mg/L e 0,21 mg/L, respectivamente, cuja atividades se mantiveram após um período de conservação de um ano a -10oC. As microesferas de Bti, Bti + óleo essencial de C. rhamnifolioides e microesferas de óleo de C. rhamnifolioides em alginato a 2% não apresentaram atividade larvicida, enquanto as microesferas preparadas em alginato a 1% apresentaram 90% de mortalidade, quando se utilizou 3x 104 UFC/g Bti imobilizado. Os resultados obtidos mostraram viabilidade para o uso de microesferas de Bti associado ao óleo essencial de C. rhamnifolioides para o controle de Aedes Aegypti. Diante dos resultados obtidos, os desafios da técnica de microencapsulamento foram estudados para o estabelecimento de parâmetros de tempo de exposição, armazenamento e concentrações na obtenção de microesferas com eficiência larvicida

Aedes aegypti (Diptera: Culicidae): populational studies and integrated strategies for vector control in the Recife Metropolitan municipalities, from 2001 to 2007

Made available in DSpace on 2012-05-07T14:40:40Z (GMT). No. of bitstreams: 2 license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) 000025.pdf: 7633350 bytes, checksum: d854bca312b99f921e3306f543eb1c1a (MD5) Previous issue date: 2008Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Recife, PE, Brasil.Reduzir a infestação por Aedes aegypti nas áreas de transmissão da dengue no Brasil continua sendo um desafio. O objetivo deste estudo foi avaliar novas abordagens para o monitoramento e controle desta espécie em municípios pernambucanos, no período de 2001 a 2007. Armadilhas de oviposição (OVT) contendo o biolarvicida Bacillus thuringiensis israelensis (Bti) e infusão de gramíneas foram utilizadas para verificar a infestação por Aedes em 18 bairros do Recife e seis bairros de Jaboatão, bem como para monitorar casa-casa 127 imóveis no bairro do Engenho do Meio (EM), em ciclos de 21 dias, por 12 meses. A coleta de ovos demonstrou a presença de Aedes spp em todos os bairros com níveis de infestação variando de 28,6 por cento a 94,4 por cento e densidade de 30,5 a 224,4 ovos/OVT em Recife e de 15,6 por cento a 87,5 por cento e 24,2 a 233,5 ovos/OVT em Jaboatão. A. aegypti predominou na maioria dos bairros, e A. albopictus foi mais abundante naqueles com maior cobertura vegetal. O estudo longitudinal revelou que o uso contínuo das OVT permitiu detectar flutuações populacionais e locais de concentração do mosquito. Um produto à base de Bti desenvolvido localmente para o controle de A. aegypti foi testado. A avaliação em laboratório e campo simulado revelou que o produto foi eficaz, com atividade residual de seis meses, estabilidade de armazenamento de dois anos e reciclagem em criadouros de Aedes. Estratégias baseadas na integração das OVT às ações de controle larvar foram implementadas de forma contínua em Nossa Senhora de Fátima (NSF)/Moreno-PE ou descontínua no Engenho do Meio (EM) e Casa Forte/Parnamirim (CFP)/Recife.O uso prolongado (4 anos) de 2 ovitrampas-controle (OVT-C)/imóvel resultou na eliminação de milhares de ovos do mosquito e na redução sustentada da densidade de Aedes em NSF/Moreno. Em CFP e EM, 5.602 OVT-C instaladas na 1ª intervenção, potencialmente recolheram mais de 13 milhões de ovos, em cinco meses, na 2ª intervenção, cerca de 2.500 OVT-C instaladas em EM, coletaram mais de 18 milhões, em 12 meses. Os resultados mostram que: a coleta/destruição massiva de ovos integrada ao tratamento larvicida dos criadouros causou impacto negativo sobre a população de Aedes spp; o uso descontínuo das OVT-C levou a uma redução temporária de sua densidade. O controle de A. aegypti através de ovitrampas é uma estratégia promissora que depende da abrangência e do tempo de uso das armadilhas em campo e conseqüentemente do número de ovos destruído

Diapause and quiescence: dormancy mechanisms that contribute to the geographical expansion of mosquitoes and their evolutionary success

Abstract Mosquitoes are insects belonging to the order Diptera and family Culicidae. They are distributed worldwide and include approximately 3500 species, of which about 300 have medical and veterinary importance. The evolutionary success of mosquitoes, in both tropical and temperate regions, is due to the various survival strategies these insects have developed throughout their life histories. Of the many adaptive mechanisms, diapause and quiescence, two different types of dormancy, likely contribute to the establishment, maintenance and spread of natural mosquito populations. This review seeks to objectively and coherently describe the terms diapause and quiescence, which can be confused in the literature because the phenotypic effects of these mechanisms are often similar

Development of a Bacillus sphaericus tablet formulation and its evaluation as a larvicide in the biological control of Culex quinquefasciatus

This study aimed to analyze the final fermentation culture of Bacillus sphaericus 2362, standardize it and develop an active tablet formulation for use in urban mosquito breeding sites. It was performed in three phases: analysis and standardization of a B. sphaericus fermented culture; physical, chemical, and biological analysis of the active powder (solubility, residual humidity, particle size, resting angle, flowing off time, compacted density, and biological activity against Culex quinquefasciatus larvae); and the development of fast-disintegrating tablets. Five formulations with differing compositions were developed and a UV protector was added to the selected formulation. The formulation products with or without UV protector, as well as the active powder caused 100% larval mortality from 1 day to 2 months after a single treatment under simulated field conditions. These results show that the UV protector does not affect the initial larvicide activity of B. sphaericus, nor its persistence over a period of two months

Fitness cost in field and laboratory Aedes aegypti populations associated with resistance to the insecticide temephos

Abstract Background The continued use of chemical insecticides in the context of the National Program of Dengue Control in Brazil has generated a high selective pressure on the natural populations of Aedes aegypti, leading to their resistance to these compounds in the field. Fitness costs have been described as adaptive consequences of resistance. This study evaluated the biological and reproductive performance of A. aegypti strains and a field population resistant to temephos, the main larvicide used for controlling mosquitoes. Methods Comparative tests were performed with a resistant field population from the municipality of Arcoverde, Pernambuco State, Brazil, with a high rate of temephos resistance (RR = 226.6) and three isogenetic laboratory strains from the same origin (Araripina municipality, Pernambuco): RecR (RR = 283.6); RecRNEx (RR = 250.5), a strain under a process of resistance reversion; and RecRev (RR = 2.32), a reversed susceptible strain used as an experimental control. Results Our study revealed that the absence of selective pressure imposed by exposure to temephos, for five consecutive generations, led to a discrete reduction of the resistance ratio and the response of the detoxifying enzymes. Most of the 19 biological parameters were impaired in the resistant strains and field population. The analysis of the fertility life table confirmed the presence of reproductive disadvantages for the resistant individuals. Similarly, the longevity, body size, and total energetic resources were also lower for the resistant females, except for the last two parameters in the field females (Arcoverde). In contrast, the sex ratio and embryonic viability suffered no interference in all strains or population evaluated, regardless of their status of resistance to temephos. Conclusions The reproductive potential and survival of the resistant individuals were compromised. The parameters most affected were the larval development time, fecundity, net reproduction rate, and the generational doubling time. These fitness costs in the natural population and laboratory strains investigated are likely associated with maintaining the metabolic mechanism of resistance to temephos. Our results show that despite these costs, the highly temephos resistant populations can compensate for these losses and successfully overcome the control actions that are based on the use of chemical insecticides

Long-term exposure of Aedes aegypti to Bacillus thuringiensis svar. israelensis did not involve altered susceptibility to this microbial larvicide or to other control agents

Abstract Background Bacillus thuringiensis svar. israelensis (Bti) is an effective and safe biolarvicide to control Aedes aegypti. Its mode of action based on four protoxins disfavors resistance; however, control in endemic areas that display high mosquito infestation throughout the year requires continuous larvicide applications, which imposes a strong selection pressure. Therefore, this study aimed to investigate the effects of an intensive Bti exposure on an Ae. aegypti strain (RecBti), regarding its susceptibility to Bti and two of its protoxins tested individually, to other control agents temephos and diflubenzuron, and its profile of detoxifying enzymes. Methods The RecBti strain was established using a large egg sample (10,000) from Recife city (Brazil) and more than 290,000 larvae were subjected to Bti throughout 30 generations. Larvae susceptibility to larvicides and the activity of detoxifying enzymes were determined by bioassays and catalytic assays, respectively. The Rockefeller strain was the reference used for these evaluations. Results Bti exposure yielded an average of 74% mortality at each generation. Larvae assessed in seven time points throughout the 30 generations were susceptible to Bti crystal (resistance ratio RR ≤ 2.8) and to its individual toxins Cry11Aa and Cry4Ba (RR ≤ 4.1). Early signs of altered susceptibility to Cry11Aa were detected in the last evaluations, suggesting that this toxin was a marker of the selection pressure imposed. RecBti larvae were also susceptible (RR ≤ 1.6) to the other control agents, temephos and diflubenzuron. The activity of the detoxifying enzymes α- and β-esterases, glutathione-S-transferases and mixed-function oxidases was classified as unaltered in larvae from two generations (F19 and F25), except for a β-esterases increase in F25. Conclusions Prolonged exposure of Ae. aegypti larvae to Bti did not evolve into resistance to the crystal, and no cross-resistance with temephos and diflubenzuron were recorded, which supports their sustainable use with Bti for integrated control practices. The unaltered activity of most detoxifying enzymes suggests that they might not play a major role in the metabolism of Bti toxins, therefore resistance by this mechanism is unlikely to occur. This study also highlights the need to establish suitable criteria to classify the status of larval susceptibility/resistance

Culicidae fauna (Diptera: Culicidae) survey in urban, ecotonal and forested areas, from the Moreno municipality - Pernambuco State, Brazil

Submitted by Ana Beatriz Oliveira ([email protected]) on 2019-04-17T12:47:47Z No. of bitstreams: 1 Culicidae fauna (Diptera.pdf: 1174592 bytes, checksum: dffe5f81b31b50733ae384310570b764 (MD5)Approved for entry into archive by Ana Beatriz Oliveira ([email protected]) on 2019-04-17T13:13:16Z (GMT) No. of bitstreams: 1 Culicidae fauna (Diptera.pdf: 1174592 bytes, checksum: dffe5f81b31b50733ae384310570b764 (MD5)Made available in DSpace on 2019-04-17T13:13:16Z (GMT). No. of bitstreams: 1 Culicidae fauna (Diptera.pdf: 1174592 bytes, checksum: dffe5f81b31b50733ae384310570b764 (MD5) Previous issue date: 2018Núcleo de Vigilância à Saúde e do Meio Ambiente. Moreno, PE, Brasil.Instituto Tecnológico de Pernambuco. Recife, PE, Brasil.Núcleo de Vigilância à Saúde e do Meio Ambiente. Moreno, PE, Brasil.Núcleo de Vigilância à Saúde e do Meio Ambiente. Moreno, PE, Brasil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Pós-Graduação em Biociências e Biotecnologia em Saúde. Recife, PE, Brasil / Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Pós-Graduação em Biociências e Biotecnologia em Saúde. Recife, PE, Brasil / Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Pós-Graduação em Biociências e Biotecnologia em Saúde. Recife, PE, Brasil / Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Pós-Graduação em Biociências e Biotecnologia em Saúde. Recife, PE, Brasil / Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.Introduction: Mosquitoes are vectors of several pathogens in tropical regions. However, information on Culicidae in the northeast region of Brazil is scarce despite many municipalities having environmental conditions favorable for these insects. Methods: We collected mosquitoes monthly for one year from urban, ecotonal, and ecological reserve areas in Moreno, Brazil, by using CDC Miniature light traps, aspiration, ovitraps, and liquid suction. Results: We collected 1,401 insects in the Culicidae family. Fifteen species of seven genera of Culicidae were identified and five specimens were identified only at the genus level. Conclusions: There is a wide diversity of mosquito species in the sampled areas, some of which are important for human health