Mosquitos are developing resistance against safe, recommended insecticides, increasing the threat of diseases like malaria and dengue. But now, researchers say they’ve developed a new way to break down even high levels of resistance: an electrostatic coating that boosts mosquito exposure to insecticides. According to findings published in Proceedings of the National Academy of Sciences this week, nets treated with this coating killed 100% of certain highly-resistant mosquito strains.
Pyrethroids are widely used synthetic chemical insecticides that work by altering nerve function and causing paralysis. Pest control tools such as insecticidal nets are often coated, impregnated, or sprayed with pyrethroids. However, prolonged use of these nets results in mosquitoes being exposed to a progressively smaller dosage of insecticides as the chemicals dissipate over time (and washes). One consequence of this sort of exposure is selection for resistant populations.
To find a way to overcome pyrethroid resistance, an international team led by Marit Farenhorst of In2Care designed netting with a charged surface – an electrostatic coating – that was originally developed for trapping pollen in the air. Insecticides are then applied onto this coated netting. The charged surface binds insecticide particles more effectively than an untreated surface, so it exposes pesky bloodsuckers to a higher amount of insecticide. The team tested its electrostatic netting on multiple resistant strains, including Anopheles, Aedes, and Culex mosquitoes. The team saw significantly higher mortality rates among resistant mosquitoes exposed to insecticide on electrostatic netting than with commercially available insecticidal netting.
In fact, for certain resistant strains, insecticide combined with electrostatic netting killed 100% of the mosquitoes. By contrast, conventional netting killed less than 10%. Mortality remained high even when the mosquitoes landed on the netting for just five seconds and also when the researchers treated the nets with a 15-fold lower dose of insecticides than that of conventional netting.
This novel resistance-breaking tool improved the effectiveness of multiple kinds of insecticides, not just pyrethroids. The researchers think the coating could be used around the house on walls, curtains, and screens. However it’s not suitable for bednets since these are directly handled by people and washed repeatedly, which would reduce efficiency.