Molecular and metabolic mechanisms of pyrethroid resistance in <i>Anopheles gambiae</i> complex (Diptera: Culicidae) in West Africa: a systematic review

Abstract

Malaria continues to pose a considerable global health concern, especially in sub-Saharan Africa, where the prevalence is most acute. In the year 2023, over 263 million cases, with an associated 597,000 deaths, were reported across the world population. Despite the historical efficacy of indoor residual spraying (IRS) and long-lasting insecticide-treated bed nets (LLITNs), the emergence and swift proliferation of insecticide resistance in mosquito populations, particularly to pyrethroids, now jeopardize the effectiveness and success of these interventions. This systematic review provides a comprehensive overview of the molecular and biochemical mechanisms underlying pyrethroid resistance in Anopheles gambiae, using the PRISMA 2020 guidelines to identify and screen relevant studies. Relevant literature was sourced from databases including PubMed, ScienceDirect, MDPI, and Scopus from 2000 to 2025, using specific search terms such as "pyrethroid resistance," "deltamethrin," "Anopheles gambiae," and "sub-Saharan or West Africa." Inclusion criteria targeted original studies assessing metabolic and genetic mechanisms in An. gambiae complex. In total, 22 studies fulfilled the inclusion criteria. L1014F and L1014S mutations were commonly reported mechanisms, while the N1575Y mutation also appeared in some West African studies. Metabolic resistance was widely reported, with overexpression of CYP450s and GSTs in several regions. Conclusively, the resistance of An. gambiae to pyrethroid is widespread and multifactorial, with co-occurrence of target-site and metabolic mechanisms across West Africa. These findings highlight the need for enhanced molecular surveillance, functional validation of resistance markers, a call for responsible administration of agricultural pesticides, and evidence-based insecticide rotation strategies to sustain the effectiveness of malaria vector control.