Meta-analysis on the entomological effects of differentially treated ITNs in a multi-site experimental hut study in sub-Saharan Africa

Abstract

Background: Restricting the placement of active ingredients (AIs) to specific panels on insecticide-treated nets (ITNs) has the potential to reduce the amount of AI required to treat a net. If the restricted placement of the AIs can exploit mosquito behaviour, particularly where they interact with the bed net interface, and not impact the net's effectiveness, then the reduction in AI could result in cost reductions. Methods: Nine individual experimental hut trials were conducted to compare the efficacy of three different hybrid net designs relative to fully treated nets; roof-only treated nets, side-only treated nets, and nets with treated roof and pyrethroid-only side panels. These trials were conducted on a range of net products with different AIs, across a range of geographies in Africa (East and West), vector species (An. gambiae, An. coluzzii, An. arabiensis, and An. funestus), hut designs (east and west African style) and hosts (cows and humans). The combined data from these trials were analysed in a meta-analysis, and odds ratios for the effect of the different net designs on mortality and blood-feeding were estimated using mixed effects logistic regression. Results: The results of this meta-analysis demonstrated that fully treated nets provide greater mosquito killing and reduction in blood-feeding effects than any configuration of insecticide treatment restricted to specific panels. Conclusions: This meta-analysis showed that hybrid net strategies that restrict the insecticide treatment to specific panels of an ITN do not give equivalency or superiority in either mortality or blood-feeding inhibition to fully treated nets. The implications of these findings are discussed.