Author(s): Gunasekaran K, Vaidyanathan K
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Abstract The wash resistance of factory produced PermaNets (with deltamethrin bonded to the netting with a resin) was studied by bioassays with Anopheles stephensi. Commercial detergent powders were used to wash the nets. For comparison, conventionally treated nets were washed and bio-assayed. Nets were washed under laboratory conditions using a Rotary shaker for 10min. Mosquito bioassays used standard WHO plastic cones with an exposure time of 3min. The PermaNet caused almost a 100\% mortality of An. stephensi after up to 18 washes and >80\% mortality up to 26 washes but after 30 washes mortality declined. The differences between the mortality of An. stephensi on treated nets washed with detergent or soap (uncoloured, non-perfumed) were not significant. When conventional nets dipped in deltamethrin (25mg/m(2)) or lambdacyhalothrin (10mg/m(2)) were washed under similar laboratory conditions, the wash resistance was markedly less than that of the PermaNet. In the case of deltamethrin, mosquito mortality remained >80\% up to 12 washes and with lambdacyhalothrin mortality remained above 80\% up to 11 washes. The relationship of 80\% mortality from a 3min bioassay to effectiveness against free flying mosquitoes remains to be determined.
This article was published in Acta Trop
and referenced in Journal of Tropical Diseases & Public Health