Emerging Pyrethroid Resistance among in Kenya.

Vector control programs, particularly in the form of insecticide-treated bed nets (ITNs), are essential for achieving malaria elimination goals. Recent reports of increasing knockdown resistance () mutation frequencies for in Western Kenya heightens the concern on the future effectiveness of ITNs in Kenya. We examined resistance in populations across Kenya through mutations and World Health Organization-recommended bioassays. We detected two alleles, L1014F and L1014S. mutations were found in five of the 11 study sites, with mutation frequencies ranging from 3% to 63%. In two Western Kenya populations, the L1014F allele frequency was as high as 10%. The L1014S frequency was highest at Chulaimbo at 55%. Notably, the L1014F mutation was found to be associated with pyrethroid resistance at Port Victoria, but mutations were not significantly associated with resistance at Chulaimbo, which had the highest mutation frequency among all sites. This study demonstrated the emerging pyrethroid resistance in and that pyrethroid resistance may be related to mutations. Resistance monitoring and management are urgently needed for this species in Kenya where resistance is emerging and its abundance is becoming predominant. mutations may serve as a biomarker for pyrethroid resistance in .