ABSTRACT
BACKGROUND: The purpose of this study was to establish whether the "bottle assay", a tool for monitoring insecticide resistance in mosquitoes, can complement and augment the capabilities of the established WHO assay, particularly in resource-poor, logistically challenging environments. METHODS: Laboratory reared Aedes aegypti and field collected Anopheles darlingi and Anopheles albimanus were used to assess the suitability of locally sourced solvents and formulated insecticides for use with the bottle assay. Using these adapted protocols, the ability of the bottle assay and the WHO assay to discriminate between deltamethrin-resistant Anopheles albimanus populations was compared. The diagnostic dose of deltamethrin that would identify resistance in currently susceptible populations of An. darlingi and Ae. aegypti was defined. The robustness of the bottle assay during a surveillance exercise in the Amazon was assessed. RESULTS: The bottle assay (using technical or formulated material) and the WHO assay were equally able to differentiate deltamethrin-resistant and susceptible An. albimanus populations. A diagnostic dose of 10 microg a.i./bottle was identified as the most sensitive discriminating dose for characterizing resistance in An. darlingi and Ae. aegypti. Treated bottles, prepared using locally sourced solvents and insecticide formulations, can be stored for > 14 days and used three times. Bottles can be stored and transported under local conditions and field-assays can be completed in a single evening. CONCLUSION: The flexible and portable nature of the bottle assay and the ready availability of its components make it a potentially robust and useful tool for monitoring insecticide resistance and efficacy in remote areas that require minimal cost tools.
Subject(s)
Aedes/drug effects , Anopheles/drug effects , Disease Vectors , Insect Control/methods , Insecticides/pharmacology , Nitriles/pharmacology , Pyrethrins/pharmacology , Animals , Humans , Insecticide Resistance , Peru , Sensitivity and SpecificityABSTRACT
Objetivos: Determinar el efecto de volteo (knockdown) y mortalidad en la medición de la eficacia residual del insecticida deltametrina 5 por ciento SC usado en el control vectorial de la enfermedad de Chagas sobre tres tipos de substratos (sillar, ladrillo y concreto) a dosis de 25 mg/m2. Materiales y métodos: Se aplicó la deltametrina en casas de diferente material en unazona endémica de Arequipa, Perú, luego fueron expuestas por 72 horas entre 87 a 120 ninfas V de Triatoma infestans enlas paredes tratadas, posteriormente las ninfas fueron transferidas a recipientes limpios para determinar el knockdown,la mortalidad a 15 días y la recuperación. Este experimento fue realizado a las 24 horas, 30, 60, 90 y 120 días posttratamiento. Resultados: La mortalidad de la deltametrina se fue reduciendo de 95% en las 24 primeras horas a 34 por ciento en el cuarto mes posterior a la exposición, independientemente del tipo de substrato, a un ritmo de 14,5 por ciento mensual (p menor que 0,001;r 2=0,79), el knockdown se mantuvo por encima de 75 por ciento al cuarto mes y la recuperación fue aumentando con el tiempo (p menor que 0,001; r2=0,77). Según substrato, se evidencia una persistencia de la mortalidad mayor que 50 por ciento hasta los 60 días para sillar, y 90 días para el ladrillo y concreto. Conclusiones: Se demostró una baja efectividad de deltametrina 5 por ciento SC a cuatro meses después del tratamiento sobre diferentes superficie (sillar, ladrillo y concreto). Es necesario tener en cuenta estos resultados para calcular los tiempos de aplicación de este insecticida en los programas de control vectorial.
Objectives: To determine knockdown and mortality in the measurement of the residual efficacy of deltamethrinformulated insecticide 5 percentage SC used in Chagas disease vector control on three types of substrates (sillar [white local volcanic rock], brick and concrete) to doses of 25mg/m2. Material and methods: We applied the deltamethrin in house with different construction material in an endemic zone of Arequipa, Peru, 87 to 120 third-stage nymphs V of Triatoma infestans was exposed by 72 hours to the treated surfaces, the nymphs were transferred to clean containers to determine mortality to 15 days, as well as knockdown and recovery. This experiment was carried out at 24 hours, 30, 60, 90 and120 days post-treatment. Results: The mortality of the deltamethrin was reduced from 95 percentage in the fist 24 hours to 34 percentage in the fourth month after exposure, regardless of the type of substrate, to a monthly rate of 14,5 percentage (p minor than 0,001; r2=0,79), the knockdown was maintained above 75 percentage in the fourth month recovery was increased over time (p minor than 0,001; r2=0,77). According substrate, we found a persistent mortality mayor than 50 porcentage to 60 days for sillar, and 90 days for the brick and concrete.Conclusions: We showed the low effectiveness of deltamethrin 5% SC to four months after the treatment on differentsubstrates (sillar, brick and concrete). It is necessary to take into account these results to calculate the time of applicationof this pesticide on vector control programmes.
Subject(s)
Vector Control of Diseases , Efficacy , Insecticides , Triatoma , Longitudinal Studies , PeruABSTRACT
Objetivo: Comparar tres tipos de atrayentes a oviposición para la detección de Aedes aegypti (agua loca, infusión de pasto Stenotaphrum secundatum y solución acuosa de propinato de metilo al 0,5 por ciento) en tres ciudades endémicas de Dengue del Perú. Materiales y métodos: Entre setiembre y octubre del 2001 se realizó un muestreo dirigido en viviendas de localidades de las provincias de Tarapoto (departamento de San Martín), Satipo (Junín) y Tumbes (Tumbes) en base al antecedente de haber presentado un caso confirmado de dengue o la presencia de pupas y larvas de Ae.aegypti a la inspección. En cada vivienda se colocaron 4 ovitrampas (con las 3 soluciones y una solución control: agua mineral) y se observaron por 3 días consecutivos, inspeccionándolas cada 24 horas. Para el análisis se empleó el test de rango múltiple de Duncan y la prueba de Dunnett, siendo significativo un p<0,05. Resultados: De 248 ovitrampas instaladas (88 en Tarapoto, 88 en Satipo y 72 en Tumbes) en 62 lugares, resultaron positivas 13,7 por ciento. El promedio global de huevos por ovitrampa fue 8,02 (rango: 0-131) y se encontró que el promedio de huevos en la infusión de pasto fue mayor al encontrado en las otras soluciones (p<0,05). Conclusiones: La infusión de pasto resultó la más efectiva sustancia atrayente en las ovitrampas empleadas para detectar Ae.aegypti.
Objective: To compare three types of oviposition baits (local water, Stenotaphrum secundatum solution and 0.5%-methyl propionate solution) for the detection of Aedes aegypti in three Dengue endemic cities in Peru. Materials and methods: Based upon one confirmed Dengue case and in the occurrence of Aedes pupae and larvae, a selective sampling of houses in Tarapoto (San Martfn), Satipo (Junin) and Tumbes (Tumbes) was performed between September and October, 2001. Four traps (containing the three solutions, as well as a control solution: mineral water) were placed in each house and observed for a 3-day period, being supervised every 24 hours. The Duncan Multiple Test and the Dunnet Test (significance level, p < 0,05) were used to perform the analysis. Results: Of 248 traps placed (88 in Tarapoto, 88 in Satipo and 72 in Tumbes) in 62 houses, 13.7% were positive. The average egg content for each trap was 8,02 (range: 0-131) and the average egg content found in the vegetable infusion was higher than those met in the other solutions (p<0,05). Conclusion: The vegetable infusion is the most effective trap bait used for detection of Aedes aegypti.
