Emergence and spatial distribution of knockdown resistance in a suburban population of Aedes albopictus

BACKGROUND: Aedes albopictus is a major vector of arboviral diseases and is often targeted by pyrethroid-based mosquito control in residential areas. While knockdown resistance (kdr) mutations are well-documented in Ae. aegypti, their emergence in Ae. albopictus has been less studied, particularly in suburban environments, where insecticide application is often uncoordinated. Understanding the temporal and spatial dynamics of resistance evolution in this context is critical for preserving the effectiveness of public health interventions. METHODS: We conducted longitudinal sampling of Ae. albopictus populations in Wake County, North Carolina, from 2016 to 2024. Using a novel allele-specific PCR melt curve assay, we genotyped 2,669 mosquitoes at the F1534S locus in the voltage-gated sodium channel gene. Resistance allele frequencies were calculated annually and mapped across the county for three key years, representing the pre-emergence (2016), initial detection (2018), and widespread phases of resistance development (2023). Selection and dominance were estimated using the Wright-Fisher approximate Bayesian computation algorithm for locus F1534S. RESULTS: The F1534S resistance allele was first detected in 2018 at a central neighborhood in Wake County. By 2023, the allele had become distributed throughout the sampling region, with the highest observed frequencies near the site of first detection. Resistance allele frequency peaked at 0.36 in 2023, accompanied by an increase in heterozygous and homozygous resistance genotypes. Temporally sampled sites showed consistent trends in rising frequencies of the resistance allele, with all temporally sampled locations harboring resistance genotypes by 2022. The resistance allele was estimated to have a high selection coefficient and to be partially recessive in this population. CONCLUSIONS: Our findings reveal rapid emergence and spatial distribution of the F1534S kdr allele in a suburban population of Ae. albopictus. The observed distribution of resistance alleles is consistent with strong genetic selection. These results highlight the need for proactive resistance monitoring and integrated management strategies that address private-sector contributions to insecticide selection pressure.