Deltamethrin Resistance Profiling in Anopheles gambiae: A Study in Ota, Ogun State, Nigeria

Abstract

Abstract Pyrethroids account 89.9% of all vector control insecticide use in African in terms of normal spray coverage This study aims to identify mosquito breeding sites and assess the knockdown resistance (kdr) gene responsible for pyrethroids resistance of Anopheles populations in Ota. Anopheles larvae collected from the Atan and Nestle (6⁰ 40' N, 3⁰ 09' E & 6⁰ 41’N, 3⁰ 9’E) were grown to adulthood in an insectary. Female mosquitoes (2-5days old) not blood-fed were evaluated for sensitivity to 0.05% deltamethrin using the standard method of the World Health Organization. To distinguish the An. gambiae complex related species, rDNA intergenic spacers were amplified using PCR. The kdr- genes were genotyped in Anopheles gambiae females. 438 female mosquitos were gathered in total; Aedes (11.17%), Anopheles (28.8%) and Culex (50.9%) being the most abundant species specimens collected. WHO bioassay for exposure to deltamethrin mortality rate for Anopheles species was 39% (Atan) and 37% (Nestle) respectively. Anopheles mosquitoes were resistant to deltamethrin. Anopheles gambiae was found as the main vector within Ota. The Probit model was utilised to obtain the median knockdown time; KDT50 and KDT95 for both sites (Nestle; KDT50 = 45.829 Min, KDT 95 = 88.854 Min & Atan; KDT 50= 44.957 Min, KDT95 = 93.473 Min). The total frequency of the kdr allele (i.e., kdr-W) resistant individuals was 0.86 in Atan and 0.796 in Nestle site. This data, despite being preliminary, highlights the importance of monitoring An. gambiae numbers in these areas to develop an effective approach for managing pyrethroid and DDT resistance in mosquito control. Susceptibility to pyrethroids can be partially restored when used alongside synergist (e.g Piperonyl butoxide- PBO) suggesting likely involvement of metabolic resistance.