Bendiocarb resistance and <em>kdr</em> associated deltamethrin and DDT resistance in <em>Anopheles gambiae s.l.</em> populations from North Eastern Adamawa State, Nigeria

Abstract

Timely and consistent insecticide resistance monitoring efforts are required for early planning of management strategies. Here, we present the first report on bendiocarb, deltamethrin and dichlorodiphenyltrichloroethane (DDT) insecticide resistance in Anopheles gambiae s.l. populations from Adamawa, North Eastern Nigeria. Mosquitoes reared from larval collections were exposed to DDT (4%), bendiocarb (0.1%) and deltamethrin (0.05%) insecticides using standard WHO test kits and protocols. Species-specific Polymerase Chain Reaction (PCR) and PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) assays were used to determine the sibling species composition of the exposed mosquitoes while allele-specific PCR was used for kdr genotyping in the mosquitoes that survived after insecticide exposure. Mosquito populations from all the four study sites in Vimtim, Imburu, Muchala and Bachure were resistant (≤ 87% mortality) to DDT and deltamethrin insecticides. Mosquito populations exposed to bendiocarb showed suspected resistance in Vimtim and Imburu study sites and confirmed resistance in Muchala and Bachure sites respectively. Mosquitoes alive after deltamethrin, DDT and bendiocarb exposures were identified predominantly as An. coluzzii species (78.5 - 92%) compared to An. gambiae s.s (5.3 - 11%) and An. arabiensis (0 - 10.1%). All the 22 kdr positive mosquitoes collected were identified as An. coluzzii. Percentage occurrence of kdr alleles in the mosquito populations alive after deltamethrin and DDT exposures were 30% and 25% respectively. An. coluzzii (≥ 63%) was the predominant species identified in each study site compared to An. gambiae sensu stricto (s.s) (≤ 20%) and An. arabiensis (≤ 17.4%) species. The results of kdr associated pyrethroid resistance is a potential threat to the effectiveness of the currently deployed deltamethrin-impregnated bed-net campaigns in Adamawa state. Evidence of bendiocarb carbamate resistance also implies potential ineffectiveness of future bendiocarb Indoor Residual Spraying. The involvement of metabolic resistance mechanisms in the mosquitoes from these study sites should be investigated for proper insecticide resistance management.

Keywords

• anopheles gambiae mosquitoes, insecticide resistance, kdr, malaria vector control, nigeria