Biology subjects

Syme, T.

Publications and source records attributed to Syme, T..

2 recordsLinked to original sources

bioRxiv2021

Can pyrethroid-piperonyl butoxide (PBO) nets reduce the efficacy of indoor residual spraying with pirimiphos-methyl against pyrethroid-resistant malaria vectors?

As the uptake of pyrethroid-PBO ITNs increases, their combination with IRS insecticides could become an operational reality in many malaria-endemic communities. Pirimiphos-methyl is a pro-insecticide requiring activation by mosquito cytochrome P450 enzymes to induce toxicity while PBO blocks activation of these enzymes in pyrethroid-resistant vector mosquitoes. PBO may thus antagonise the toxicity of pirimiphos-methyl IRS when combined with pyrethroid-PBO ITNs. The impact of combining two major brands of pyrethroid-PBO ITNs (Olyset(R) Plus, PermaNet(R) 3.0) with pirimiphos-methyl IRS (Actellic(R) 300CS) was evaluated against pyrethroid-resistant Anopheles gambiae sl in two parallel experimental hut trials in southern Benin in comparison to bendiocarb IRS and each intervention alone. The wild vector population was resistant to pyrethroids but susceptible to pirimiphos-methyl and bendiocarb. PBO pre-exposure partially restored deltamethrin toxicity but not permethrin. Mosquito mortality in experimental huts was significantly improved in the combinations of bendiocarb IRS with Olyset(R) Plus (33%) and PermaNet(R) 3.0 (38%) compared to bendiocarb IRS alone (14-16%, p<0.001), demonstrating an additive effect. Conversely, mortality was significantly reduced in the combinations of pirimiphos-methyl IRS with Olyset(R) Plus (59%) and PermaNet(R) 3.0 (55%) compared to pirimiphos-methyl IRS alone (77-78%, p<0.001), demonstrating an antagonistic effect. Combining pirimiphos-methyl IRS with the pyrethroid-PBO ITNs provided significantly improved mosquito mortality (55-59%) compared to the pyrethroid-PBO ITNs alone (22-26%) and improved blood-feeding inhibition relative to the IRS alone. This study provided evidence of an antagonistic effect when pyrethroid-PBO ITNs were combined with pirimiphos-methyl IRS in the same household resulting in lower levels of vector mosquito mortality compared to the IRS alone. Pirimiphos-methyl IRS also showed potential to significantly enhance malaria control when deployed to complement pyrethroid-PBO ITNs in an area where PBO fails to fully restore susceptibility to pyrethroids.

zoology↗

bioRxiv2020

Efficacy of broflanilide (VECTRON T500), a new meta-diamide insecticide, for indoor residual spraying against pyrethroid-resistant malaria vectors.

The rotational use of insecticides with different modes of action for indoor residual spraying (IRS) is recommended for improving malaria vector control and managing insecticide resistance. A more diversified portfolio of IRS insecticides is required; insecticides with new chemistries which can provide improved and prolonged control of insecticide-resistant vector populations are urgently needed. Broflanilide is a newly discovered insecticide being considered for malaria vector control. We investigated the efficacy of a wettable powder (WP) formulation of broflanilide (VECTRON T500) for IRS on mud and cement wall substrates in WHO laboratory and experimental hut studies against pyrethroid-resistant malaria vectors in Benin, in comparison with pirimiphos-methyl CS (Actellic(R) 300CS). There was no evidence of cross-resistance to pyrethroids and broflanilide in CDC bottle bioassays. In laboratory cone bioassays, mortality of susceptible and pyrethroid-resistant A. gambiae s.l. with broflanilide WP treated substrates was >80% for 6-14 months. At application rates of 100mg/m2 and 150 mg/m2, mortality of wild pyrethroid-resistant A. gambiae s.l. entering treated experimental huts in Cove, Benin was 57%-66% with broflanilide WP and did not differ significantly from pirimiphos-methyl CS (57-66% vs. 56%, P>0.05). Mosquito mortality did not differ between the two application rates and local wall substrate-types tested (P>0.05). Throughout the 6-month hut trial, monthly wall cone bioassay mortality on broflanilide WP treated hut walls remained >80% for both susceptible and resistant strains of A. gambiae s.l.. Broflanilide shows potential to significantly improve the control of malaria transmitted by pyrethroid-resistant mosquito vectors and would thus be a crucial addition to the current portfolio of IRS insecticides. One Sentence SummaryVECTRON T500, a new wettable powder formulation of broflanilide developed for indoor residual spraying, showed high and prolonged activity against wild pyrethroid-resistant malaria vectors, on local wall substrates, in laboratory bioassays and experimental household settings in Benin.

evolutionary biology↗