Resistência das populações de Aedes (Stegomyia) aegypti (Linnaeus, 1762) (Insecta, Diptera, Culicidae) aos inseticidas utilizados para o controle: estado da arte do conhecimento / Resistance of Aedes (Stegomyia) aegypti (Linnaeus, 1762) (Insecta, Diptera, Culicidae) populations to insecticides used for control: art state of knowledge

Introdução: cerca de quatro bilhões de pessoas residem em áreas com risco de dengue, uma arbovirose transmitida pelo mosquito Aedes (Stegomyia) aegypti (Linnaeus, 1762) (Insecta, Diptera, Culicidae). Na tentativa de combater esse vetor e reduzir a disseminação da dengue, o meio de controle vetorial frequentemente utilizado são os inseticidas. Entretanto, o uso indiscriminado destes no controle do mosquito está relacionado aos mecanismos de resistência desse vetor. Objetivo: mapear as evidências científicas relacionadas à resistência do mosquito A. aegypti aos inseticidas utilizados para o controle populacional. Metodologia: revisão de escopo, segundo metodologia Instituto Joana Briggs, em bases de dados indexadas: PubMed, Embase, CINAHL, Web of Science, SCOPUS e Biblioteca Virtual em Saúde. Através do mnemônico PCC (população, conceito e contexto), elaborou-se a estratégia de busca utilizando descritores do Decs e Mesh. Resultados: foram encontrados 1.631 estudos sobre a temática. Após critérios de elegibilidade e seleção, foram incluídos 30 estudos específicos sobre resistência do Aedes aegypti a inseticidas foram incluídos na revisão. A maior parte tratou de forma experimental e 28 (93,3%) estudos trabalharam o controle químico. Em relação à resistência a inseticidas, em 20 estudos (66,6%) constatou-se resistência metabólica e em 9 (30%) a resistência mediada pela alteração da variabilidade genética. Os estudos que observaram mutação não deixam claro se a mutação gênica é especificamente devido à ação mutagênica aos inseticidas. Conclusões:o A. aegypti desenvolve adaptações que lhe conferem resistência aos inseticidas, sendo que esses mecanismos de resistência estão relacionados à variabilidade genética e a adaptações metabólicas, que são transmitidas a seus descendentes ao longo das gerações. Assim, torna-se necessário um avanço nos estudos visando não apenas identificar e explicar os mecanismos de resistência, mas encontrar meios alternativos de manejo que possam controlar o inseto sem ocasionar resistência aos mesmos.

Introduction: about four billion people live in areas at risk of dengue, an arbovirus transmitted by the Aedes (Stegomyia) aegypti (Linnaeus, 1762) (Insecta, Diptera, Culicidae). To combat this vector and reduce the spread of dengue, the means of vector control often used are insecticides. However, their indiscriminate use in mosquito control is related to the resistance mechanisms of this vector. Objective: to map the scientific evidence related to the resistance of the Aedes aegypti mosquito to the insecticides used to control dengue. Methodology: scope review, according to the Joana Briggs Institute methodology, in indexed databases: PubMed, Embase, CINAHL, Web of Science, SCOPUS and Virtual Health Library. Using the mnemonic PCC (population, concept and context), a search strategy was developed using Decs and Mesh descriptors. Results: 1,631 studies on the subject were found. After eligibility and selection criteria, 30 specific studies on Aedes aegypti resistance to insecticide were included in the review . Most treated experimentally and 28 (93.3%) studies worked on chemical control. Regarding the resistance to insecticide, in 20 studies (66.6%) there was found metabolic resistance and in 9 (30%) resistance mediated by modification on the genetic variability. Studies that have looked at mutation do not make it clear whether the gene mutation is specifically due to mutagenic action of insecticides. Conclusions: Aedes aegypti develops adaptations that gives them resistance to insecticides, and these resistance mechanisms are related to genetic variability and to metabolic adaptations, which are transmitted to its descendants over generations. Thus, it is necessary to perform advance in studies aiming not only to identify and explain the resistance mechanisms, but to find alternative means of management that can control the insect without causing resistance to them.

Resistencia a insecticidas en Aedes aegypti y Aedes albopictus (Diptera: Culicidae) de Tapachula, Chiapas, México / Insecticide resistance in Aedes aegypti and Ae. albopictus (Diptera: Culicidae) populations from Tapachula, Chiapas, Mexico

Resumen: Objetivo: Determinar la resistencia a insecticidas en Ae. aegypti y Ae. albopictus de Tapachula, Chiapas, México. Material y métodos: Se utilizaron ovitrampas para obtener huevos de mosquitos Aedes y se realizaron pruebas de susceptibilidad (CDC) y ensayos enzimáticos con la primera generación. Resultados: Aedes aegypti mostró resistencia a deltametrina, permetrina, malatión, clorpirifos, temefos y a bendiocarb (CARB), mientras que Aedes albopictus a malatión y en menor grado a cloripirifos, temefos, permetrina y deltametrina. Ambas especies mostraron altos niveles de enzimas como citocomo P450 y glutatión S-tranferasa, mientras que los niveles de esterasas variaron por especie y sitio muestreado. Se detectó acetilcolinesterasa insensible a insecticidas en ambas especies. Conclusión: En un hábitat urbano de Tapachula, Chiapas, México donde se aplica control con insecticidas Ae. aegypti y Ae. albopictus sólo son susceptibles al propoxur.

Abstract: Objective: To determine the insecticide resistance status of Ae. aegypti and Ae. albopictus from Tapachula, México. Materials and methods: Mosquito eggs were collected with the use of ovitraps and CDC susceptibility bioassays and biochemical assays were conducted to determine resistance levels and resistance mechanisms, respectively. Results: Ae. aegypti showed resistance to deltamethrin and permethrin (PYRs), malathion, chlorpyrifos and temephos (OP), and to bendiocarb (CARB), while Ae. albopictus showed resistance to malathion and to a lesser intensity to chlorypirifos, temephos, permethrin and deltamethrin. Both species showed high levels of P450 and GSTs, while levels of esterases varied by species and collection site. Altered acethilcholinesterase was detected in both species. Conclusion: In an urban habitat from Tapachula, Chiapas, Mexico where vector control using insecticides takes place, Ae. aegypti and Ae. albopictus are only susceptible to propoxur.

Assessing the efficacy of two new formulations of larvicide pyriproxyfen for the control of Aedes aegypti using dissemination stations in two sites of Rio de Janeiro city

BACKGROUND Aedes aegypti is the primary transmitter of several arbovirus with great impact in human health. Controlling vector mosquitoes is an essential and complex task. One promising control method is to use mosquitoes as a vehicle to disseminate tiny particles of juvenile-killing insecticides, such as pyriproxyfen (PPF), to breeding sites. OBJECTIVES We aimed to investigate the capacity of Ae. aegypti to disseminate two new formulations of PPF in two sites of Rio de Janeiro city for assessment of the efficacy of these products. METHODS Dissemination stations impregnated with powder and liquid new formulations of PPF were installed in two test sites. Ovitraps were used in the test sites and in a control site for monitoring the presence of Ae. aegypti throughout eggs collection. FINDINGS Entomological indices indicated that the new formulations of PPF were efficient in reducing eggs abundance. Liquid formulation performed better than powder formulation. Ready-to-use formulations of PPF can be quickly applied in the field and can be replaced after a few months. MAIN CONCLUSIONS New formulations of PPF associated with mosquito dissemination approach make a valuable vector control strategy, managing to cover places of difficult access for whatever reason. New formulations application requires less labour, being economically attractive.

Susceptibility of Aedes aegypti populations to pyriproxyfen in the Federal District of Brazil

Abstract INTRODUCTION: In Brasilia, pyriproxyfen (PPF; 0.01 mg/L) has been used for the larval control of Aedes aegypti mosquitoes since 2016. Information on the susceptibility of Ae. aegypti to PPF, and the development of resistance in populations from the Federal District of Brazil (FD) is limited. It is essential to monitor the susceptibility of Ae. aegypti to insecticides in order to improve vector control strategies. This study aimed to evaluate the susceptibility of Ae. aegypti populations from five areas of Brasilia to PPF. METHODS: We performed dose-response tests to estimate the emergence inhibition and resistance ratio of each field population, including the Rockefeller reference population. We also analyzed egg positivity, and the density and mortality of larvae and pupae. RESULTS: Populations from Vila Planalto (RR50=1.7), Regiment Guards Cavalry (RR50=2.5), and Sub-secretary of Justice Complex (RR50=3.7) presented high susceptibility to PPF, while the RR values of populations from Lago Norte (RR50=7.7) and Varjão (RR50=5.9) were moderately high, suggesting the emergence of insipient resistance to PPF in Brasilia. At 30 ng/mL, the highest larvae mortality rate was 2.7% for the population from Lago Norte, while that of pupae was 92.1% for Varjão and Vila Planalto. CONCLUSIONS: The five populations of Ae. aegypti from the FD are susceptible to PPF and there is a need to monitor the susceptibility of Ae. aegypti in new areas of the FD.

Chemical composition and larvicidal activities of essential oil of Cinnamomum camphora (L. ) leaf against Anopheles stephensi

Abstract INTRODUCTION Anopheles stephensi is the main malaria vector in Southeast Asia. Recently, plant-sourced larvicides are attracting great interests. METHODS: The essential oil was extracted from the leaf of Cinnamomum camphora (L.), and a bioassay was conducted to determine the larvicidal efficacy. The chemical composition of the essential oil was determined by GC-MS analysis. RESULTS: The oil showed strong, dose-dependent larvicidal activities. The onset of larvicidal efficiency was rapid. The LC50 and LC95 were determined as 0.146% and 1.057% at 1 h, 0.031% and 0.237% at 12 h, 0.026% and 0.128% at 24 h, respectively. The oil contains 32 compounds. CONCLUSIONS The essential oil of C. camphora leaf has an excellent larvicidal potential for the control of A. stephensi.

Spatiotemporal multiple insecticide resistance in Aedes aegypti populations in French Guiana: need for alternative vector control

BACKGROUND Aedes aegypti is the sole vector of urban arboviruses in French Guiana. Overtime, the species has been responsible for the transmission of viruses during yellow fever, dengue, chikungunya and Zika outbreaks. Decades of vector control have produced resistant populations to deltamethrin, the sole molecule available to control adult mosquitoes in this French Territory. OBJECTIVES Our surveillance aimed to provide public health authorities with data on insecticide resistance in Ae. aegypti populations and other species of interest in French Guiana. Monitoring resistance to the insecticide used for vector control and to other molecule is a key component to develop an insecticide resistance management plan. METHODS In 2009, we started to monitor resistance phenotypes to deltamethrin and target-site mechanisms in Ae. aegypti populations across the territory using the WHO impregnated paper test and allelic discrimination assay. FINDINGS Eight years surveillance revealed well-installed resistance and the dramatic increase of alleles on the sodium voltage-gated gene, known to confer resistance to pyrethroids (PY). In addition, we observed that populations were resistant to malathion (organophosphorous, OP) and alpha-cypermethrin (PY). Some resistance was also detected to molecules from the carbamate family. Finally, those populations somehow recovered susceptibility against fenitrothion (OP). In addition, other species distributed in urban areas revealed to be also resistant to pyrethroids. CONCLUSION The resistance level can jeopardize the efficiency of chemical adult control in absence of other alternatives and conducts to strongly rely on larval control measures to reduce mosquito burden. Vector control strategies need to evolve to maintain or regain efficacy during epidemics.

Liaisons dangereuses: cross-border gene flow and dispersal of insecticide resistance-associated genes in the mosquito Aedes aegypti from Brazil and French Guiana

BACKGROUND In recent years, South America has suffered the burden of continuous high impact outbreaks of dengue, chikungunya and Zika. Aedes aegypti is the main mosquito vector of these arboviruses and its control is the only solution to reduce transmission. OBJECTIVES In order to improve vector control it is essential to study mosquito population genetics in order to better estimate the population structures and the geneflow among them. METHODS We have analysed microsatellites and knockdown resistance (kdr) mutations from a trans-border region in Amazonia between the state of Amapá (Brazil) and French Guiana (overseas territory of France), to provide further knowledge on these issues. These two countries have followed distinct vector control policies since last century. For population genetic analyses we evaluated variability in 13 well-established microsatellites loci in Ae. aegypti from French Guiana (Saint Georges and Cayenne) and Brazil (Oiapoque and Macapá). The occurrence and frequency of kdr mutations in these same populations were accessed by TaqMan genotype assays for the sites 1016 (Val/Ile) and 1534 (Phe/Cys). FINDINGS We have detected high levels of gene flow between the closest cross-border samples of Saint-Georges and Oiapoque. These results suggest one common origin of re-colonisation for the populations of French Guiana and Oiapoque in Brazil, and a different source for Macapá, more similar to the other northern Brazilian populations. Genotyping of the kdr mutations revealed distinct patterns for Cayenne and Macapá associated with their different insecticide use history, and an admixture zone between these two patterns in Saint Georges and Oiapoque, in accordance with population genetic results. MAIN CONCLUSIONS The present study highlights the need for regional-local vector surveillance and transnational collaboration between neighboring countries to assess the impact of implemented vector control strategies, promote timely actions and develop preparedness plans.

Larvicidal activity of essential oil from Vitex negundo and Vitex trifolia on dengue vector mosquito Aedes aegypti

Abstract INTRODUCTION: The ability of Vitex trifolia and Vitex negundo essential oils to kill Aedes aegypti and Culex quinquefasciatus larvae was evaluated. METHODS: The larvae were treated with their respective essential oils at 50-125 ppm concentration. RESULTS: LC50 and LC90 for V. trifolia against Ae. aegypti and C. quinquefasciatus, and those for V. negundo against Ae. aegypti were 57.7+0.4, 77.9+0.9 ppm and 55.17+3.14, 78.28+2.23 ppm, and 50.86+0.9, 73.12+1.3 ppm, respectively. Eucalyptol and caryophyllene were the major components in Vitex trifolia and Vitex negundo essential oil, respectively. CONCLUSIONS: This study revealed potential larvicidal properties of essential oil from V. trifolia.

Bio-efficacy, physical integrity, community usage and washing practices of mosquito nets treated with ICON MAXX long-lasting insecticidal treatment in India

BACKGROUND New brands of potential long lasting insecticide nets (LLINs) and LLIN treatment kits require field evaluation before they are used in a vector control programme. OBJECTIVES The aim of this study was to evaluate the bio-efficacy, usage, washing practice and physical integrity of nets treated with LLIN treatment kit, ICON MAXX in a phase III field trial in Odisha state, India. METHODS A total of 300 polyester nets treated with ICON MAXX and 140 polyester nets treated conventionally with lambda-cyhalothrin CS 2.5% ITNs were distributed. The bio-efficacy was evaluated with WHO cone bioassay. The chemical analysis of netting pieces was done at the beginning, after 12 and 36 months of the trial. FINDINGS After one year of distribution of nets, the bioassay showed 100% mortality on both ITNs and ICON MAXX treated nets. At 36 months, the overall pass rate was 58.8% and the mean lambda-cyhalothrin content of LLINs was 34.5 mg ai/m2, showing a loss of 44.4% of the original concentration. CONCLUSION ICON MAXX treated LLIN was found to retain bio-efficacy causing 97% knockdown of Anopheles stephensi up to 30 months and met the WHOPES criteria. However, the desired bio-efficacy was not sustained up to 36 months.