Insecticide resistance dynamics in Anopheles gambiae s.l. in Ghana

Malaria control in Ghana and sub-Saharan Africa is threatened by widespread insecticide resistance in Anopheles gambiae s.l., undermining the effectiveness of long-lasting insecticidal nets and indoor residual spraying. A longitudinal survey was conducted between 2023 and 2025 across 20 urban and suburban sites spanning the coastal savannah, forest, and Sahel savannah zones. Of the 1,008 An. gambiae s.l. sampled, An. coluzzii was the dominant species (65.1%), followed by An. gambiae s.s. (18.9%) and An. arabiensis (10.9%). WHO bioassays revealed high pyrethroid resistance (mortality rate = 20–45%). Full susceptibility to pirimiphos-methyl (mortality rate = 99–100%) and chlorfenapyr was observed at most sites, though resistance to clothianidin was observed in Obuasi, Tema, and Abossey Okai. Intensity assays confirmed strong pyrethroid resistance even at 10× diagnostic concentrations. Genotyping showed near-fixation of the kdrL995F allele and the presence of additional resistance markers, including N1570Y, V402L, I1527T, and Ace-1R G280S.