A 6.5-kb intergenic structural variation enhances P450-mediated resistance to pyrethroids in malaria vectors lowering bed net efficacy

Leon M J Mugenzi, Benjamin D Menze, Magellan Tchouakui, Murielle J Wondji, Helen Irving, Micareme Tchoupo, Jack Hearn, Gareth D Weedall, Jacob M Riveron, Fidelis Cho-Ngwa, Charles S Wondji

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Elucidating the complex evolutionary armory that mosquitoes deploy against insecticides is crucial to maintain the effectiveness of insecticide-based interventions. Here, we deciphered the role of a 6.5-kb structural variation (SV) in driving cytochrome P450-mediated pyrethroid resistance in the malaria vector, Anopheles funestus. Whole-genome pooled sequencing detected an intergenic 6.5-kb SV between duplicated CYP6P9a/b P450s in pyrethroid-resistant mosquitoes through a translocation event. Promoter analysis revealed a 17.5-fold higher activity (p < .0001) for the SV- carrying fragment than the SV- free one. Quantitative real-time PCR expression profiling of CYP6P9a/b for each SV genotype supported its role as an enhancer because SV+/SV+ homozygote mosquitoes had a significantly greater expression for both genes than heterozygotes SV+/SV- (1.7- to 2-fold) and homozygotes SV-/SV- (4-to 5-fold). Designing a PCR assay revealed a strong association between this SV and pyrethroid resistance (SV+/SV+ vs. SV-/SV-; odds ratio [OR] = 2,079.4, p < .001). The 6.5-kb SV is present at high frequency in southern Africa (80%-100%) but absent in East/Central/West Africa. Experimental hut trials revealed that homozygote SV mosquitoes had a significantly greater chance to survive exposure to pyrethroid-treated nets (OR 27.7; p < .0001) and to blood feed than susceptible mosquitoes. Furthermore, mosquitoes homozygote-resistant at the three loci (SV+/CYP6P9a_R/CYP6P9b_R) exhibited a higher resistance level, leading to a far superior ability to survive exposure to nets than those homozygotes susceptible at the three loci, revealing a strong additive effect. This study highlights the important role of structural variations in the development of insecticide resistance in malaria vectors and their detrimental impact on the effectiveness of pyrethroid-based nets.

Original languageEnglish
Pages (from-to)4395-4411
Number of pages17
JournalMolecular Ecology
Issue number22
Publication statusPrint publication - Nov 2020
Externally publishedYes

Bibliographical note

© 2020 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.


  • Africa, Eastern
  • Africa, Southern
  • Africa, Western
  • Animals
  • Anopheles/genetics
  • Cytochrome P-450 Enzyme System/genetics
  • Insecticide Resistance/genetics
  • Insecticides/pharmacology
  • Malaria/prevention & control
  • Mosquito Vectors/genetics
  • Pyrethrins
  • Anopheles funestus
  • insecticide resistance
  • bed net
  • structural variant


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