Comparison of deltamethrin tablet formulation with liquid deltamethrin andpermethrin for bednet treatment in The Gambia

The study aim was to compare three formulations, tablet deltamethrin, liqui d deltamethrin and liquid permethrin, for their impact on vector behaviour and persistence. Product acceptance, perceived side-effects and user's perc eptions of effectiveness were also investigated. At the beginning of the 19 98 rainy season, 255 nets in a Gambian village were dipped in one of the th ree insecticides. Chemical residue analysis immediately after dipping showe d that the target doses were reached for the liquid insecticides, but table t deltamethrin deposited significantly less. Insecticide persistence at 5 m onths, however, was highest for the tablet formulation. Susceptibility test s established that Anophelines in this area were sensitive to both insectic ides. All three formulations appeared effective as very few live Anopheline s, or other mosquitoes, were caught under the treated nets. This conclusion was supported by the bioassay data with both deltamethrin formulations giv ing over 90% mortality soon after dipping and at 3 months, and at 5 months 70.8 and 79.6% were obtained for deltametrin liquid and tablet, respectivel y. Permethrin appeared less effective at all times (72.4, 86.8, 59.0%). The re were no serious side-effects reported by the villagers following dipping . All three treatments were perceived as effective by the majority (92%) of users and most (93%) wanted to use the insecticide again. Deltamethrin tab lets thus appear as good as permethrin for treating bednets in The Gambia. In addition, a tablet formulation is considerable easier to pack and distri bute.