Susceptibility Status of Anopheles gambiae to selected Insecticides in parts of Benue State, North Central Nigeria

Vector control remains the preferred method for effective malaria control. The impressive results of vector control are however,  threatened by emerging resistance to insecticides among Anopheles gambiae s.l. mosquitoes. This study aimed at determining the pattern  of resistance to selected insecticides in each class of carbamates, organochlorines, organophosphates, and pyrethriods using  World Health Organisation tubes and Centre for Disease prevention and Control standard bottle assay protocols. Larvae and pupae of        Anopheles mosquitoes were collected in villages of Buruku and o Katsina-Ala Local Government Areas of Benue State between April and  May 2019 and reared at 27 C and 80% relative humidity to adults at the Nasarawa state University Insectary. Susceptibility tests were  carried out on 2-3 days old non- blood fed female adults. With WHO test method, Anopheles mosquitoes were completely susceptible  (100% mortality) to Primiphos-methyl (organophosphate), Lambdacyhalothrin (pyrethroids) in Buruku and Katsina Ala but were resistant  (54% mortality) to DDT (Organochlorine) in both sites. Mosquitoes were resistant (88% mortality) to Bendiocarb (Carbamates) in Katsina  Ala but susceptible in Buruku with 99% mortality. However, the results for CDC bottle bioassays showed that Anopheles mosquitoes were  susceptible to Primiphos methyl, Lambdacyhalothrin and Bendiocarb (>98% mortality) except for DDT which was resistant (<85%  mortality) in both LGAs. Overall, this study shows that Anopheles gambiae s.l are resistant to DDT. The resistance may have arisen from  indiscriminate use of the pesticide in households and for agricultural purposes. This study provides baseline and useful information on  the susceptibility status of Anopheles mosquito populations to four classes of insecticides approved for public health use. Proper  regulation should therefore be put in place on the procurement and use of this insecticide.