Insecticide Susceptibility Profile of Anopheles gambiae s.l. from Ikot-Ekpene, Akwa Ibom State, Nigeria

Background: Mosquito resistance to routinely used insecticides is threatening malaria vector control strategies in sub-Saharan Africa. This study reports the susceptibility of wild populations of Anopheles gambiae s.l. from Ikot-Ekpene, Akwa Ibom State, Southern Nigeria to insecticides.

Methods: WHO standard methods were used to detect knock-down and mortality in wild female Anopheles mosquitoes collected from 4 rural communities in Ikot-Ekpene. The WHO diagnostic doses of 0.05% deltamethrin, 0.05% lambdacyhalothrin, 0.75% permethrin and 5% malathion were used. Bioassays were performed on non-blood-fed mosquitoes of ages 2 to 3 days old. Post exposure mortality after 24 hours and knock-down values for KDT50 and KDT95 were calculated.

Results: According to WHO criteria, insecticide resistance was not recorded at any of the studied sites and for any of the tested insecticide. Knock-down within 1 hour post insecticide exposure ranged from 98.7% to 100%. Mortality after 24 hours post exposure was 100% for all insecticides except lambdacyhalothrin which averaged 99.1%. There was high variability in KDT50 and KDT95 values across the sites.

Conclusion: Since the local Anopheles gambiae populations were susceptible to all the insecticides tested, vector control campaigns employing the use of any of the insecticide would not be compromised; however, there is need for continued monitoring to ensure early detection of resistance.