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

Abstract

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.