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      Evaluación de la resistencia a insecticidas de una cepa de Aedes aegypti de El Salvador Translated title: Assessing the insecticide resistance of an Aedes aegypti strain in El Salvador

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          Abstract

          OBJETIVOS: Evaluar el nivel de susceptibilidad a insecticidas de una cepa de Aedes aegypti procedente de El Salvador y describir los posibles mecanismos de resistencia al temefós. MÉTODOS: Se evaluó una cepa de A. aegypti procedente del municipio de Soyapango, departamento de San Salvador, El Salvador. Mediante bioensayos se determinó la susceptibilidad de las larvas al insecticida organofosforado temefós y a tres piretroides (deltametrina, lambdacialotrina y cipermetrina) y de los adultos a un insecticida organofosforado (clorpirifós). Se determinó el factor de resistencia (FR50) con respecto a una cepa sensible de referencia (Rockefeller). Se estableció el mecanismo de resistencia al temefós mediante el empleo de sustancias sinergistas, ensayos bioquímicos de actividad enzimática y zimogramas en gel de poliacrilamida. RESULTADOS: Las larvas de la cepa estudiada mostraron una alta resistencia al temefós (FR50 = 24,16). De las enzimas analizadas, se encontró que solo la esterasa A4 estaba vinculada al mecanismo de resistencia al temefós. Los mosquitos adultos resultaron susceptibles a la lambdacialotrina y al clorpirifós y su resistencia a la deltametrina y la cipermetrina quedó en la categoría de verificación. CONCLUSIONES: La resistencia al temefós podría reducir la eficacia del control químico del mosquito A. aegypti en la zona estudiada de El Salvador. Los insecticidas clorpirifós, lambdacialotrina y cipermetrina son buenos candidatos alternativos a utilizar en las nuevas intervenciones de control de este vector.

          Translated abstract

          OBJECTIVES: To assess the level of insecticide susceptibility of a certain Aedes aegypti strain found in El Salvador and to explain the mechanisms for its resistance to temephos. METHODS: An A. aegypti strain from the municipality of Soyapango, Department of San Salvador, El Salvador, was studied. Bioassays were used to determine the susceptibility of the larvae to the organophosphate insecticide temephos and to three pyrethroids (deltamethrin, lambda-cyhalothrin, and cypermethrin); and of adults to an organophosphate insecticide (chlorpyrifos). The resistance factor (RF50) with determined with respect to a reference susceptible strain (Rockefeller). The mechanism of temephos resistance was determined through the use of synergistic substances, biochemical assays for enzymatic activity, and polyacrylamide gel zymograms. RESULTS: The larvae of the strain studied proved highly resistant to temephos (RF50 = 24.16). Of the enzyme samples analyzed, only the esterase A4 was linked to the mechanism of temephos resistance. The adult mosquitoes were susceptible to lambda-cyhalothrin and chlorpyrifos; and resistance to deltamethrin and cypermethrin fell into the category needing further verification. CONCLUSIONS: Temephos resistance could reduce the efficiency of chemical control of the A. aegypti mosquito in El Salvador study area. Chlorpyrifos, lambda-cyhalothrin, and cypermethrin are good alternative insecticides for use in new efforts to control this vector.

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          Resistance of Aedes aegypti to organophosphates in several municipalities in the State of Rio de Janeiro and Espírito Santo, 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.
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            Instruction for determining the susceptibility or resistance of mosquito larvae to insecticides

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              Aedes aegypti resistance to temephos during 2001 in several municipalities in the states of Rio de Janeiro, Sergipe, and Alagoas, Brazil

              For more than 30 years temephos, an organophosphate insecticide, has been the sole larvicide used in Brazil in the control of Aedes aegypti. Organophosphates were also used for adult control, being replaced by pyrethroids since l999. In this same year, the Brazilian Health Foundation started the coordination of the Ae. aegypti Insecticide Resistance Monitoring Program. In the context of this program, our group was responsible for the detection of temephos resistance in a total of 12 municipalities in the states of Rio de Janeiro (RJ), Alagoas (AL), and Sergipe (SE) during 2001. In each municipality, a pool of mosquitoes collected from different districts was used, with the exception of Rio de Janeiro city, where eight districts have been separately evaluated. Exposure of larvae to the diagnostic dose of temephos revealed resistance in all localities examined, with mortality levels ranging from 4% (Pilares district, Rio de Janeiro, RJ) to 61.9% (Campos dos Goytacazes, RJ). Quantification of mortality showed resistance ratios from 6.1 (Aracaju, SE) to 16.8 (São Gonçalo, RJ and Penha district, Rio de Janeiro, RJ). The national dengue control program is presently using these data to subside insecticide resistance management.
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                Author and article information

                Journal
                rpsp
                Revista Panamericana de Salud Pública
                Rev Panam Salud Publica
                Organización Panamericana de la Salud (Washington, Washington, United States )
                1020-4989
                1680-5348
                September 2009
                : 26
                : 3
                : 229-234
                Affiliations
                [02] Ciudad de Panamá orgnameOrganización Panamericana de la Salud orgdiv1Programa Regional de Dengue Panamá
                [03] San Salvador orgnameMinisterio de Salud orgdiv1Departamento de Entomología El Salvador
                [01] Ciudad de La Habana orgnameInstituto de Medicina Tropical Pedro Kourí Cuba bisset@ 123456ipk.sld.cu
                Article
                S1020-49892009000900007 S1020-4989(09)02600307
                10.1590/s1020-49892009000900007
                20058833
                27233b89-30ba-44d4-980b-51bb5bb8e5da

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

                History
                : 20 June 2008
                : 08 February 2009
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 30, Pages: 6
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                SciELO Public Health

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                Categories
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                insecticide resistance,Aedes,temefós,resistencia a los insecticidas,control vectorial,El Salvador,temefos,vector control

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