Molecular Characterization of Insecticide Resistance Genes in Mosquito Populations in Port Harcourt Metropolis, Rivers State, Nigeria

Monitoring and understanding the trends and mechanisms of insecticide resistance are critical for developing effective vector control strategies in Nigeria. Malaria and lymphatic filariasis remain major mosquito-borne diseases in Sub-Saharan Africa, primarily transmitted by female Anopheles and Culex mosquitoes. This study aimed to characterize the mosquito vector population and assess the insecticide resistance profile in three communities within the Obio/Akpor and Port Harcourt Local Government Areas of Rivers State, Nigeria. Mosquito larvae and pupae (Anopheles and Culex species) were collected from various habitats, reared to adulthood under controlled conditions, and morphologically identified. Insecticide susceptibility was evaluated using the CDC bottle bioassay method. The kdr mutation was detected using polymerase chain reaction (PCR) techniques applied to both resistant and susceptible adult mosquitoes exposed to pyrethroids. PCR assays were utilized to identify members of the Anopheles gambiae complex, while multiplex PCR confirmed Culex species. The CDC bioassays revealed complete susceptibility (100% mortality) to pirimiphos-methyl (organophosphate) and chlorfenapyr (pyrrole) across all sites for both Anopheles and Culex species. In contrast, high resistance was observed against pyrethroids, with mortality rates ranging from 34-53% in Anopheles mosquitoes and 64-91% in Culex quinquefasciatus. Morphological identification confirmed the presence of Anopheles and Culex spp., with an average kdr mutation frequency of approximately 90% in the three Anopheles species. Molecular analyses identified An. gambiae s.s., An. coluzzii, and An. arabiensis within the Anopheles gambiae complex, while Culex quinquefasciatus was the sole Culex species detected. Furthermore, the data suggested that kdr mutations and detoxification enzyme activity may result from environmental factors in contaminated breeding sites. These findings highlight significant public health implications, including increased nuisance biting and a heightened risk of disease transmission in polluted environments. The results underscore the urgent need for improved environmental management and targeted vector control strategies to mitigate the spread of mosquito-borne diseases in Nigeria