Insecticide resistance in Anopheles mosquitoes: mechanisms, epidemiological impact and implications for malaria control in Sub-Saharan Africa

Abstract

Malaria remains among the most formidable public health challenges confronting Sub-Saharan Africa, with the region bearing 94% of the estimated 265 million global cases recorded in 2024. The emergence and proliferation of insecticide resistance in Anopheles mosquitoes threatens to reverse decades of hard-won progress in malaria control. Kenya's experience exemplifies this crisis, with malaria cases surging 27% from 3.3 million in 2023 to 4.2 million in 2024, a trend partly attributable to intensifying resistance patterns. This review synthesizes contemporary evidence on insecticide resistance mechanisms operating in Anopheles vectors throughout Sub-Saharan Africa, examining the epidemiological context of malaria transmission, the diversity of vector species, and the multifaceted nature of resistance including target-site modifications, metabolic detoxification, cuticular alterations, and newly identified sequestration mechanisms. Current surveillance indicates that 90% of malaria-endemic nations report resistance to at least one insecticide class, while 32% demonstrate resistance across all four major insecticide classes. Documentation of intense pyrethroid resistance exceeding ten-fold diagnostic concentrations in Uganda, coupled with sporozoite infection rates reaching 20.41% in resistant populations, underscores the operational significance of this phenomenon. Environmental contaminants originating from agricultural pesticides and extractive industries constitute additional resistance drivers that operate independently of public health interventions. This review identifies critical knowledge deficiencies in resistance characterization at subnational scales and emphasizes the imperative for integrated resistance management frameworks incorporating molecular surveillance networks, genomic technologies, and evidence-informed insecticide deployment strategies. Comprehending the intricate relationships between resistance mechanisms and epidemiological outcomes proves essential for maintaining the effectiveness of existing vector control approaches and guiding the strategic deployment of next-generation interventions across malaria-endemic regions.