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 <i>Anopheles gambiae</i> 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 <i>An. gambiae</i> s.l. sampled, <i>An. coluzzii</i> was the dominant species (65.1%), followed by <i>An. gambiae</i> s.s. (18.9%) and <i>An. arabiensis</i> (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 <i>kdrL995F</i> allele and the presence of additional resistance markers, including <i>N1570Y</i>, <i>V402L</i>, <i>I1527T</i>, and Ace-1R <i>G280S</i>.