Spatial distribution and insecticide resistance of Aedes mosquitoes in Osun State: implications for vector control

Aedes mosquitoes are primary vectors of arboviral diseases, such as dengue, chikungunya, and Zika, posing major threats to tropical public health. Understanding their spatial distribution and resistance status is vital for sustainable control. This study investigated the mapping of breeding habitats, species composition, and insecticide susceptibility in Aedes populations from Osun State, Nigeria.

Larval surveys across a rural community identified 36 potential habitats, of which 27.8% were positive for Aedes breeding. A total of 3500 larvae were collected, reared to adult stage, morphologically identified and subjected to WHO-standard insecticide bioassays.

Two species were identified: Aedes aegypti (99.3%) and Aedes albopictus (0.7%), with Ae. aegypti strongly predominant (p < 0.05). Mortality rates following insecticide exposure ranged from 94 to 100%. Complete susceptibility was observed for permethrin, deltamethrin, and pirimiphos-methyl, while reduced mortality (94%) against alpha-cypermethrin indicated possible emerging resistance. The mapping of larval habitats revealed clustered breeding in rural communities, portending localized risk of arboviral transmission.

These findings highlight that while Aedes populations in the study area remain largely susceptible to conventional insecticides, early signals of resistance require proactive management by the state. Incorporating synergists into integrated vector control, alongside habitat surveillance and mapping, will be critical to sustaining insecticide effectiveness and reducing the burden of Aedes-borne diseases in Osun State and Nigeria at large.