Electrostatic coating enhances bioavailability of insecticides and breaks pyrethroid resistance in mosquitoes

Abstract

Insecticide resistance poses a significant and increasing threat to the control of malaria and other mosquito-borne diseases. We present a novel method of insecticide application based on netting treated with an electrostatic coating that binds insecticidal particles through polarity. Electrostatic netting can hold small amounts of insecticides effectively and results in enhanced bioavailability upon contact by the insect. Six pyrethroid-resistant Anopheles mosquito strains from across Africa were exposed to similar concentrations of deltamethrin on electrostatic netting or a standard long-lasting deltamethrin-coated bednet (PermaNet 2.0). Standard WHO exposure bioassays showed that electrostatic netting induced significantly higher mortality rates than the PermaNet, thereby effectively breaking mosquito resistance. Electrostatic netting also induced high mortality in resistant mosquito strains when a 15-fold lower dose of deltamethrin was applied and when the exposure time was reduced to only 5 s. Because different types of particles adhere to electrostatic netting, it is also possible to apply nonpyrethroid insecticides. Three insecticide classes were effective against strains of Aedes and Culex mosquitoes, demonstrating that electrostatic netting can be used to deploy a wide range of active insecticides against all major groups of disease-transmitting mosquitoes. Promising applications include the use of electrostatic coating on walls or eave curtains and in trapping/contamination devices. We conclude that application of electrostatically adhered particles boosts the efficacy of WHO-recommended insecticides even against resistant mosquitoes. This innovative technique has potential to support the use of unconventional insecticide classes or combinations thereof, potentially offering a significant step forward in managing insecticide resistance in vector-control operations.

Keywords: electrostatic coating; insecticide; malaria; mosquito; resistance management.

Fig. 1.

Origins of the tested pyrethroid-resistant and susceptible Anopheles strains and the field-collected Culex strain.

Fig. 2.

(A) Photograph of electrostatic netting saturated with fluorescent dust particles lighting up orange under UV light at 50× magnification. (B) A Culex mosquito contaminated with fluorescent particles after a 5-s contact with the netting. (C) Culex female with fluorescent particles after 3-min contact with netting.

Fig. S1.

Average (± SE) mortality and knockdown rates of two groups of 25 female pyrethroid-resistant anopheline strains from the Vector Control Research Unit (VCRU) measured 1 h (blue bars) or 24 h (red bars) after 1-h exposure to 0.05% deltamethrin papers in WHO test tubes.

Fig. S2.

Mortality rates of susceptible anopheline strains measured 24 h after 3-min exposure to PermaNet 2.0 netting containing 55 mg/m² deltamethrin (blue) or electrostatic netting containing 37 mg/m² deltamethrin (red).

Fig. 3.

Corrected mortality percentage (n = 50 mosquitoes per treatment) 24 h after pyrethroid-resistant anopheline mosquito strains were exposed to PermaNet netting (55 mg deltamethrin/m²; blue bars) or electrostatic netting (37 mg deltamethrin/m²; red bars) for 3 min. For each treatment, the mortality of mosquitoes exposed to insecticide was corrected for the mortality of counterparts exposed to control netting using Abbott’s formula. Asterisks indicate significant differences determined by χ² test; ***P < 0.001.

Fig. 4.

Corrected mortality percentage (n = 50 mosquitoes per treatment) 24 h after pyrethroid-resistant mosquito strains were exposed to PermaNet netting (55 mg deltamethrin/m²; blue bars), or electrostatic netting (37 mg deltamethrin/m²; red bars) for 5 s. For each treatment, the mortality of mosquitoes exposed to insecticide was corrected for the mortality of counterparts exposed to control netting using Abbott’s formula. Asterisks indicate significant differences determined by χ² test; *P < 0.05; ***P < 0.001; ns, not significant.

Fig. 5.

Corrected mortality percentage (n = 50 mosquitoes per treatment) 24 h after pyrethroid-resistant mosquito strains were exposed for 3 min to PermaNet netting coated with deltamethrin (55 mg AI/m²; blue bars), a 15-fold lower dose of deltamethrin on electrostatic netting (3.7 mg AI/m²; black bars), or a similar dose of deltamethrin on electrostatic netting (37 mg AI/m²; red bars). For each treatment, the mortality of mosquitoes exposed to insecticide was corrected for the mortality of counterparts exposed to control netting using Abbott’s formula. Asterisks indicate significant differences determined by χ² test; *P < 0.05; ***P < 0.001; ns, not significant.