Lack of fitness cost associated to
CYP9K1
‐mediated insecticide resistance in
Anopheles funestus
, re
Claudine Raïssa Keyoumbu Manyaka‐Tientcheu, Magellan Tchouakui, Carlos Simeon Djoko Tagne, Murielle J. Wondji, Flobert Njiokou, Charles Sinclair Wondji Abstract
BACKGROUND
Resistance management is critical to maintain insecticide effectiveness in malaria control, and understanding fitness costs of metabolic resistance is key for effective contingency strategies. This study investigates fitness costs linked to two key metabolic resistance mechanisms, CYP9K1 (454A) and GSTe2 (119F) in Anopheles funestus from Central Cameroon. Using DNA‐based diagnostic tools, we evaluated fitness parameters, while monitoring changes in resistance alleles frequencies across generations.
RESULTS
Our findings reveal that 454A‐ CYP9K1 confers fitness advantages, notably through accelerated pupation (RR versus SS: OR = 4.85; P < 0.0001) and extended adult longevity (RR versus SS: OR = 4.91; P = 0.0001). By contrast, 119F‐ GSTe2 showed no significant impact on the mosquito's life traits. No significant correlation was observed between the expression of CYP9K1 or GSTe2 and life traits such as adult lifespan, larval development ( P = 0.2 and P = 0.1, respectively), or oviposition. After 13 generations without insecticide exposure, despite the absence of the homozygous‐resistant 454A/A‐ CYP9K1 genotype, the 454A‐ CYP9K1 resistance allele persisted at moderate frequencies (0.39–0.32), indicating a slow reversal of susceptibility. Contrarily, a faster recovery of susceptibility was observed for GSTe2 , with the 119F‐ GSTe2 resistance allele declining from 0.14 to complete absence.
CONCLUSION
These findings elucidate how fitness costs shape insecticide resistance reversal. Although removing insecticide pressure can promote susceptibility restoration, the process might be slower for some ( CYP9K1 ) yet faster for others ( GSTe2 ). Moreover, increased vector longevity associated with resistance could enhance malaria transmission potential. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.