Site specific bioefficacy of dual active insecticide treated nets against highly pyrethroid resistant Anopheles gambiae s.l. in Burkina Faso

Abstract Insecticide-treated nets have substantially lowered malaria case s and deaths, but increasing insecticide resistance in malaria vectors threatens this progress. Burkina Faso is among the countries with the highest insecticide resistance levels, challenging vector control. This study assessed the efficacy of unwashed, washed and aged standard, Interceptor G2 (IG2) and Royal Guard (RG) nets against highly resistant Anopheles gambiae s.l. (< 10% mortality to alpha-cypermethrin 0.05%) in Experimental Hut Trials in Tengrela and Tiefora, Burkina Faso over three rainy seasons. Of the 22,234 mosquitoes collected, 66.6% were An. gambiae s.l., with Anopheles coluzzii predominating in Tengrela and An. gambiae s.s. in Tiefora. Unwashed IG2 nets induced the highest 72-h mortality (57% in Tiefora and 34% and Tengrela) significantly outperforming standard nets. Mortality was lower in An. coluzzii than in An. gambiae (Odds Ratio: 0.5, 95% CI 0.3–0.7). Washing or aging reduced the efficacy of both IG2 and RG nets. Only washed RG nets successfully reduced blood feeding compared with standard nets. RG nets also drastically reduced An. gambiae s.l. offspring indicating a significant sublethal effect. The findings highlight the influence of local vector composition and net condition on IG2 and RG nets performance and support targeted deployment strategies and monitoring.