Rising of pyrethroid resistance mutations (kdr) in the dengue vector Aedes aegypti from northeastern Argentina

Insecticide resistance poses a significant threat to the control of the main dengue vector, Aedes aegypti . Knockdown resistance mutations (kdr) have been associated with pyrethroid resistance and embody the primary source of genetically resistant mosquitoes. This study describes the evolution of two kdr mutations, V1016I and F1534C, in Ae. aegypti from Posadas, Argentina, based on TaqMan genotyping data generated from two sampling times, 2019 and 2024, at the same collection sites. Consistent with global studies, we observed a significant increase in the frequency of these kdr alleles (>14%) after 5 years, where 93% of samples had at least two kdr alleles. Most remarkably, the number of highly resistant mosquitoes carrying three or four kdr alleles have expanded 25% in 5 years. The rapid rise in pyrethroid genetic resistance might result from the intense insecticide use during dengue outbreaks. This 5% yearly rate trend highlights the need to integrate routine genetic resistance monitoring into vector control programs, and to adopt alternative strategies to prevent further erosion of insecticides efficacy.