Determination of the Preliminary Discriminating Concentration of Broflanilide Against Malaria Vector Mosquito Anopheles gambiae by Multi-Centre Susceptibility Testing

Indoor residual spraying (IRS) of insecticides is widely used as an effective method to control malaria vector mosquitoes in sub-Saharan Africa. In 2023, a new IRS product, VECTRON™ T500 (Mitsui Chemicals Crop & Life Solutions, Inc.), was launched. This product contains broflanilide, a novel active ingredient for IRS, and has been confirmed to exhibit long-lasting insecticidal efficacy against malaria vector mosquitoes. However, the discriminating concentration to assess the susceptibility of wild Anopheles populations to broflanilide has not yet been determined. In this study, WHO bottle bioassays were conducted in nine research facilities to collect dose-response data on broflanilide against adult female mosquitoes of the insecticide susceptible Anopheles gambiae s.s. Kisumu strain. These data were statistically analysed and validated following WHO guidelines, and it was determined that the preliminary discriminating concentration of broflanilide for An. gambiae mosquitoes should be 18 μg/bottle. The results of this study will provide a useful benchmark for susceptibility monitoring of wild mosquito populations in regions of sub-Saharan Africa into which VECTRON™ T500 is being introduced for malaria vector control.