Changes in Knockdown Resistance (kdr) Allele Frequencies in Anopheles gambiae Populations Before and After Long-Lasting Insecticidal Net Distribution in Nasarawa and Plateau States, North-Central Nigeria
Background: The effectiveness of long-lasting insecticidal nets (LLINs) is threatened by the emergence of pyrethroid resistance in malaria vectors. This study assessed changes in knockdown resistance (kdr) allele frequencies in Anopheles gambiae populations before and after LLIN distribution in selected communities of Nasarawa and Plateau States, Nigeria.
Methods:A total of 1,152 Anopheles gambiae sensu lato mosquitoes collected from Gbuwhen, Maiganga, Lankan, and Seri were analyzed. Mosquitoes obtained during pre-LLIN and post-LLIN periods were genotyped for the kdr mutation using polymerase chain reaction (PCR). Allelic frequencies calculated and compared between periods using Pearson’s chi-square test.
Results: Overall kdr prevalence increased significantly from 143 positive mosquitoes during the pre-LLIN period to 247 during the post-LLIN period (χ² = 36.44, p < 0.001). Marked increases were observed in Maiganga (28.5% to 79.0%) and Seri (44.9% to 100%), whereas Gbuwhen showed a slight decline (9.3% to 5.7%) and no kdr-positive mosquitoes were detected in Lankan after LLIN distribution.
Conclusion: LLIN deployment was associated with significant changes in kdr allele frequencies across study communities. Continuous molecular surveillance and integrated insecticide resistance management are required to sustain malaria vector control interventions in North-Central Nigeria.
Keywords: Anopheles gambiae, knockdown resistance, kdr mutation, pyrethroid resistance, LLINs, malaria vector control/surveillance, Molecular epidemiology and Alleleic frequency.
