RESUMO
Introducción. La resistencia fisiológica de Aedes aegypti constituye una de las principales amenazas para la eficacia de los programas de control de la transmisión del dengue. Objetivos. Determinar el estado de la sensibilidad a los insecticidas en poblaciones naturales de A. aegypti de tres localidades endémicas para dengue en Casanare. Materiales y métodos. Se obtuvieron mosquitos adultos de A. aegypti a partir de estados inmaduros recolectados en siete poblaciones naturales correspondientes a tres municipios. La primera generación filial fue empleada para evaluar los mecanismos bioquímicos asociados con alteración de ß -esterasas inespecíficas y enzimas monooxigenasas del grupo citocromo P450. La segunda generación permitió evaluar la sensibilidad a los insecticidas a partir de bioensayos, usando la metodología propuesta por los Centers for Disease Control and Prevention para mosquitos adultos y la técnica para larvas de la Organización Mundial de la Salud. Resultados. Todas las poblaciones evaluadas registraron resistencia al organoclorado DDT y a los piretroides lambdacialotrina y permetrina. Dos presentaron sensibilidad a la deltametrina y cinco a la ciflutrina. Se registró sensibilidad a los organofosforados temefos, malatión y fenitrotión. Ninguna población incrementó las ß -esterasas, pero sí incrementaron las enzimas P450 en dos poblaciones de Yopal. Conclusiones. Los resultados sugieren que las enzimas P450 pueden jugar un papel importante en la resistencia a los piretroides y al DDT; aun así, otros mecanismos de resistencia pueden estar actuando en las poblaciones. La sensibilidad a los insecticidas organofosforados permitiría continuar con el uso de este grupo químico para interrumpir la transmisión del dengue en Casanare.
Introduction: Physiological resistance of Aedes aegypti is a major threat to effective control programs in the transmission of dengue virus. Objective: To determine the status of susceptibility to insecticides used in public health, in natural populations of A. aegypti from three endemic dengue localities of Casanare. Materials and methods: Adult mosquitoes were recovered from A. aegypti immature stages from seven natural populations collected for three municipalities. The first filial generation was used to assess the biochemical mechanisms associated with loss of susceptibility: nonspecific esterase (NSE) and enzyme cytochrome P450 monooxygenases group. The second filial generation allowed us to evaluate the susceptibility to insecticides from bioassays using the CDC 1998 methodology for adult mosquitoes and WHO 1981 technique for larvae. Results: In the seven adult populations recorded loss of susceptibility to organochlorine DDT and pyrethroids lambda-cyhalothrin and permethrin. Two populations showed susceptibility to deltamethrin and five populations showed susceptibility to cyfluthrin. There was a susceptibility to organophosphates temephos, malathion and fenitrothion in all populations. No population showed increased NSE but an increase of P450 in two populations Conclusions: It appears that the P450 may play an important role in resistance to pyrethroids and DDT, still other resistance mechanisms may be acting in populations. Susceptibility to organophosphate allows continued use of this chemical group to interrupt transmission of dengue in Casanare.
Assuntos
Animais , Aedes , Inseticidas , Saúde Pública , Colômbia , Resistência a InseticidasRESUMO
INTRODUCTION: Physiological resistance of Aedes aegypti is a major threat to effective control programs in the transmission of dengue virus. OBJECTIVE: To determine the status of susceptibility to insecticides used in public health, in natural populations of A. aegypti from three endemic dengue localities of Casanare. MATERIALS AND METHODS: Adult mosquitoes were recovered from A. aegypti immature stages from seven natural populations collected for three municipalities. The first filial generation was used to assess the biochemical mechanisms associated with loss of susceptibility: nonspecific esterase (NSE) and enzyme cytochrome P450 monooxygenases group. The second filial generation allowed us to evaluate the susceptibility to insecticides from bioassays using the CDC 1998 methodology for adult mosquitoes and WHO 1981 technique for larvae. RESULTS: IN the seven adult populations recorded loss of susceptibility to organochlorine DDT and pyrethroids lambda-cyhalothrin and permethrin. Two populations showed susceptibility to deltamethrin and five populations showed susceptibility to cyfluthrin. There was a susceptibility to organophosphates temephos, malathion and fenitrothion in all populations. No population showed increased NSE but an increase of P450 in two populations CONCLUSIONS: It appears that the P450 may play an important role in resistance to pyrethroids and DDT, still other resistance mechanisms may be acting in populations. Susceptibility to organophosphate allows continued use of this chemical group to interrupt transmission of dengue in Casanare.
