Long-term impact of exposure to Royal Guard, a pyriproxyfen-based bed net, on pyrethroid-resistant malaria vectors from Cameroon using DNA-based metabolic resistance markers.

BACKGROUND

Escalating pyrethroid resistance in malaria vectors highlights the urgency of implementing new control tools incorporating non-pyrethroid molecules. Here, using DNA-based metabolic resistance markers, we assessed the efficacy of the dual active ingredients net Royal Guard against pyrethroids-resistant malaria vectors in Cameroon, establishing its long-term impact on mosquitoes' life traits after exposure.

RESULTS

Cone assays revealed low efficacy of Royal Guard against field Anopheles populations. However, analysis of the survival curves revealed that unexposed mosquitoes lived longer (11.4 ± 0.4 days) than those exposed to Royal Guard (7.9 ± 0.2 days) (χ2 = 6; P = 0.05), indicating that despite the lower immediate mortality observed against resistant mosquitoes, there is a long-term effect on Anopheles funestus longevity. High blood-feeding inhibition rate was observed (44-80% versus 11-41%), indicating that this net has a negative impact on blood meal intake. Additionally, female mosquitoes exposed to this net exhibited a 25% reduction in oviposition, 18.30% reduction in fecundity, 8.10% reduction in offspring, and a 74.74% infertility rate compared to the control. Genotyping of key resistance markers revealed that, metabolic markers and L1014F-Kdrw are associated with the reduced efficacy observed, with homozygote-resistant mosquitoes significantly more able to survive and live longer after exposure than homozygote-susceptible mosquitoes (odds ratio = 15.79; confidence interval = 5.35-43.27; P < 0.0001).

CONCLUSION

This study revealed that although pyrethroid-resistant mosquitoes have higher ability to survive and live longer after exposure to Royal Guard, this net significantly affects their lifespan, blood-feeding ability and interestingly reduces their fecundity/fertility. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.