Efficacy of Chlorfenapyr and Clothianidin Insecticides against Permethrin Resistant Anopheles gambiae s.l. in Gidan Yaro Village, Sokoto, Nigeria

Background and Objective: The continued spread of insecticide resistance is becoming a threat to effective vector control programmes. Chlorfenapyr and clothianidin with distinct modes of action have been included in vector control programmes. This work aims to assess the susceptibility status of Anopheles gambiae s.l. to chlorfenapyr and clothianidin. Materials and Methods: Chlorfenapyr and clothianidin were tested, using CDC bottle bioassay and modified WHO susceptibility tests, respectively, against Anopheles gambiae s.l. collected from Gidan Yaro Village. Cross-resistance to permethrin, alphacypermethrin, bendiocarb and pirimiphos-methyl was assessed in the same mosquito populations using CDC bottle bioassays. Results: Complete mosquito mortality was observed using the recommended diagnostic doses for chlorfenapyr (100 μg/bottle) and clothianidin (2%/filter paper). The laboratory-reared and wild-captured mosquitoes were resistant to permethrin with mortality ranging from 62-82% and survived 2× and 5× diagnostic doses. The field population of An. gambiae s.l. was significantly more susceptible to clothianidin, reaching 100% mortality by day 3 compared to the laboratory strain which recorded 100% mortality by day 4 post-exposure. In contrast, the wild population was less susceptible to chlorfenapyr, with the highest mortality of 99% at 72 hrs using 100 μg/bottle compared to the laboratory colony, which recorded complete mortality at 100 μg/bottle by 24 hrs. Conclusion: The slow mode of action of the clothianidin and chlorfenapyr and the absence of cross-resistance make them appropriate for inclusion in the Malaria Control Programme particularly in this part of the country where malaria incidence is high.