Potent mosquitocidal effect of ivermectin-treated nettings and sprayed walls on Anopheles gambiae

Abstract Ivermectin (IVM) has been proposed as a new tool for malaria control as it is toxic on vectors feeding on treated humans or cattle. Nevertheless, IVM may have a direct mosquitocidal effect when applied on bed nets or sprayed walls. Laboratory-reared, insecticide-susceptible Kisumu Anopheles gambiae were exposed to IVM on impregnated netting materials and sprayed plastered- and mud walls using cone bioassays. All mosquitoes died within 6 hours when exposed to IVM-treated nettings, and within 18 hours for both sprayed walls. Mosquito mortality rate on the IVM-treated nettings was similar to that of positive control (100% mortality at 2 hour) while survival was significantly longer on both IVM-sprayed walls (100% mortality at 18 hour) (Log rank X2 = 36.28, p<0.001). Adjusted Cox model predicted a significant interaction between IVM treatment and surface type, as well as significantly higher mosquito mortality on IVM-treated nettings [HR=12.92 (95% CI: 7.69-18.14), p<0.001] compared to plastered- and mud walls. IVM also inhibited mosquito blood feeding and oviposition. Our results show a direct mosquitocidal effect of IVM on An. gambiae Kisumu strain and suggest its potential application as a new insecticide for effective vector control strategies.