Introduction

Aedes albopictus and Aedes aegypti are the primary vectors of arboviral diseases such as dengue, chikungunya, and yellow fever. In the absence of effective vaccines for most of these infections, vector control through insecticide use remains the primary preventive strategy. However, increasing resistance to multiple insecticide classes among Aedes mosquitoes poses a significant challenge, potentially compromising control efforts. Assessing insecticide susceptibility and resistance mechanisms is crucial for developing effective and sustainable vector management strategies. This study evaluated the insecticide susceptibility and kdr mutation frequency in Aedes populations from urban and semi-urban areas of Ibadan, Nigeria, to support targeted control interventions.

Methods

Immature Aedes mosquitoes were collected from natural and artificial breeding sites in Ibadan North (urban) and Akinyele (semi-urban) LGAs and reared to adulthood (F1 progeny). Insecticide susceptibility tests were conducted on adult mosquitoes using the CDC bottle bioassay with WHO diagnostic doses of deltamethrin, permethrin, bendiocarb, and pirimiphos-methyl. PCR assays were performed on pyrethroid-exposed mosquitoes to detect the kdr (F1534C) mutation through direct sequencing of PCR products.

Results

Insecticide susceptibility tests revealed that Aedes aegypti exhibited resistance to permethrin in both urban (89.4% ± 1.9% mortality) and semi-urban (88.9% ± 9.3% mortality) areas, whereas Aedes albopictus remained fully susceptible. Both species demonstrated complete susceptibility to pirimiphos-methyl (>99%) and bendiocarb (>99%). The kdr (F1534C) mutation frequency was low (0.06–0.22), suggesting minimal target-site resistance to pyrethroids.

Conclusion

The observed resistance of Aedes aegypti to permethrin underscores the need for continuous insecticide resistance monitoring and the adoption of rotational insecticide use in vector control programs. The low kdr mutation frequency suggests that other resistance mechanisms, such as metabolic resistance, may be involved. Implementing integrated vector management strategies is essential for the effective and sustainable control of Aedes-borne diseases.