Efficacy of bifenthrin-impregnated bednets against Anopheles funestus and pyrethroid-resistant Anopheles gambiae in North Cameroon

ABSTRACT

Background: Recent field studies indicated that insecticide-treated bednets (ITNs) maintain their efficacy despite a high frequency of the knock-down resistance (kdr) gene in Anopheles gambiae populations. It was essential to evaluate ITNs efficacy in areas with metabolic-based resistance. Methods: Bifenthrin was used in this experiment because it is considered a promising candidate for bednets impregnation. Nets were treated at 50 mg/m2; a dose that has high insecticidal activity on kdr mosquitoes and at 5 mg/m2; a dose that kills 95of susceptible mosquitoes under laboratory conditions with 3 minutes exposure. Bednets were holed to mimic physical damage. The trial was conducted in three experimental huts from Pitoa; North-Cameroon where Anopheles gambiae displays metabolic resistance and cohabits with An. funestus. Results: Bifenthrin at 50 mg/m2 significantly reduced anophelines' entry rate (80). This was not observed at 5 mg/m2. Both treatments increased exophily in An. gambiae; and to a lesser extent in An. funestus. With bifenthrin at high dosage; over 60reduction in blood feeding and 75-90mortality rates were observed in both vectors. Despite presence of holes; only a single An. gambiae and two An. funestus females were collected inside the treated net; and all were found dead. The same trends were observed with low dosage bifenthrin though in most cases; no significant difference was found with the untreated control net. Conclusion: Bifenthrin-impregnated bednets at 50 mg/m2 were efficient in the reduction of human-vector contact in Pitoa. Considerable personal protection was gained against An. funestus and metabolic pyrethroid resistant An. gambiae populations