Phenotypic evidence of deltamethrin resistance and identification of selective sweeps in Anopheles mosquitoes on the Bijagós Archipelago, Guinea-Bissau

Abstract

Vector control in the Bijagós Archipelago of Guinea-Bissau currently relies on pyrethroid insecticide-treated nets. However, data on insecticide resistance in Guinea-Bissau is limited. This study identified deltamethrin resistance in the Anopheles gambiae sensu lato complex on Bubaque island using WHO tube tests in November 2022. Whole genome sequencing of An. gambiae sensu stricto mosquitoes identified six single nucleotide polymorphisms (SNPs) previously associated with, or putatively associated with, insecticide resistance: T791M, L995F, N1570Y, A1746S and P1874L in the vgsc gene, and L119V in the gste2 gene. Twenty additional non-synonymous SNPs were identified in insecticide-resistance associated genes. Four of these SNPs were present at frequencies over 5% in the population: T154S, I126F and G26S in the vgsc gene and A65S in ace1. Genome wide selection scans using Garud's H₁₂ statistic identified two selective sweeps: one in chromosome X and one in chromosome 2R. Both selective sweeps overlap with metabolic genes previously associated with insecticide resistance, including cyp9k1 and the cyp6aa/cyp6p gene cluster. This study presents the first phenotypic testing for deltamethrin resistance and the first whole genome sequence data for Anophelesgambiae mosquitoes from the Bijagós, contributing data of significance for vector control policy in this region.