Wash resistance of PermaNets in comparison to hand-treated nets.
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.
Vector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry 605006, India. vcrc@vsnl.com
K
K
Gunasekaran
K
K
Vaidyanathan
D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000254:growth & development / Q000469:parasitology; D001512:Bedding and Linens; D001681:Biological Assay; D007194:India; D007303:Insect Vectors / Q000187:drug effects* / Q000469:parasitology; D007306:Insecticides / Q000494:pharmacology*; D007846:Laundering / Q000379:methods*; D008288:Malaria / Q000517:prevention & control; D009570:Nitriles / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*
D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin; C037304:cyhalothrin