Abstract

Malaria is a major public health problem in Nigeria, accounting for about 60% of all outpatient attendances and 30% of all hospital admissions. Indoor residual spraying (IRS) was scaled up in Nigeria to supplement long lasting insecticide treated nets (LLINs) for malaria vector control. The success of IRS partly defends on the susceptibility of local anopheles mosquitoes to insecticides. The WHO standard insecticides-impregnated papers and tubes were used to conduct bioassay tests against local populations of Anopheles species in Misau Bauchi State Nigeria with a view of selecting the suitable insecticides for IRS. The tests papers include: Cyfluthrin (0.15%), DDT (4%), Deltamethrin (0.05%), Lambdacyhalothrin (0.05%), Malathion (5%), Permethrin (0.75%), Propoxur (0.01%), Alpha-cypermethrin  (0.75%), Bendiocarb (0.1%), Bifenthrin (0.15%) and untreated (control). Twenty (20) two to three day-old, female Anopheles species, glucose fed, none blood fed, were exclusively used in the bioassay per treatments which was replicated three times. The post exposure 1 h knockdown and 24 h mortality was assessed. The results of the knockdown assessment indicate that Alphacypermethrin had the lowest KD₅₀ (time taken to knockdown fifty percent of the exposed mosquitoes) value of 4.8 min. Relatively moderate KD₅₀ values (minutes) were obtained with Propoxur (11.34), Deltamethrin (13.20), Malathion (15.82), Bendiocarb (17.29), Permethrin (18.43), Cyfluthrin (20.28) and Lambdacyhalothrin (23.11). Relatively higher KD₅₀ values were obtained with Bifenthrin (27.29) and DDT (32.12) impregnated papers. The results of mortality assessment indicate that Anopheles mosquitoes were susceptible to Alphacypermethrin, Malathion and Propoxur with 100% mortality. The Anopheles species were less susceptible to Bifenthrin, Lambdacyhalothrin, Permethrin, Deltamethrin, Bendiocarb, Cyfluthrin and DDT. The Anopheles species used in the tests were morphological identified as Anopheles gambiae, Anopheles funestus and Anopheles nili. The public health significance of these findings is discussed.

Key words: Nigeria, Anopheles mosquitoes, resistance, Misau, Bauchi State, indoor residual spraying (IRS).