Adaptation and evaluation of the bottle assay for monitoring insecticide resistance in disease vector mosquitoes in the Peruvian Amazon

Elvira Zamora Perea,Miriam Palomino Salcedo,William G Brogdon,Gregor J Devine,Rosario Balta León

doi:10.1186/1475-2875-8-208

Abstract

BackgroundThe 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.MethodsLaboratory 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.ResultsThe 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 μg 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.ConclusionThe 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.

Highlights

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, in resource-poor, logistically challenging environments
Each test replica utilised 180 females (15 mosquitoes in each of three untreated bottles and nine bottles treated with the diagnostic dose)
This paper shows that ethanol (95% purity) can be used as an alternative to acetone, and that at least some formulations can be used in place of technical grade insecticides

Summary

Introduction

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, in resource-poor, logistically challenging environments. The primary vectors of these diseases in the Amazon basin are, respectively, Aedes aegypti and Anopheles darlingi. Insecticide-based vector control is effective if optimally executed [4,5,6,7], but common barriers to implementation include limited local resources, poor operational capacity, the use of chemical classes that are resisted, and the application of adulterated insecticides. If carefully applied and calibrated, are the cheapest way to help identify many of these factors. They will characterize insect responses to different insecticide formulations, identify the presence of resistant populations and, by default, implicate application or equipment error as a cause of field control failures

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