Authors
C Wondji1; C Wondji2; 1 Centre for Research in Infectious Diseases (CRID), Yaoundé, UK; 2 Liverpool School of Tropical Medicine, Liverpool, UK Discussion
Malaria control relies on insecticide-based interventions such as insecticide-treated nets or indoor residual spraying. However, increasing resistance to main insecticides in malaria vectors threatens the continued success of these tools. To maximize the effectiveness of insecticide-based interventions, it is crucial to elucidate the genetic basis of resistance and establish its impact on malaria control. Recent studies have revealed a complex genomic evolution of resistance in malaria vectors in Africa which is likely to impact the efficacy of control tools. Target site resistance mechanisms notably knockdown resistance (kdr) markers are spreading extensively in Anopheles gambiae populations. There are extensive reports of metabolic resistance to insecticides in major malaria vectors such as An. gambiae and An. funestus with evidences that it is reducing the efficacy of pyrethroid-based interventions. Transcriptomic and genomic analyses have revealed that cytochrome P450 gene are playing a major role beside other genes including glutathione S-transferases. Whole genome sequencing has detected selective sweep footprints in mosquito populations associated with scale up of insecticide-treated nets. Furthermore, a complex evolution of metabolic resistance has selected evolutionary features including copy number variation (CNV) and structural variations. Moreover, DNA-based markers of metabolic resistance are being detected including in An. funestus and An. gambiae. These DNA-based markers are allowing to assess the resistance impact on the efficacy of insecticide-treated nets using experimental hut trials. Additionally, resistance impact is now evaluated on epidemiological parameters such as fitness cost and malaria transmission. Improvement in our understanding of molecular basis of resistance will undoubtedly implement suitable control interventions while improving resistance management strategies across Africa. 
