We report the first finding of the knockdown Leu-Phe and Leu-Ser mutations associated with resistance to pyrethroids and DDT insecticides in the malaria mosquito Anopheles gambiae from Cameroon. The Leu-Phe mutation was found in both the M and S molecular forms of An. gambiae. Importantly, two specimens of the S molecular form were found to carry both mutations in a heterozygous state.
Insecticides are a key component of vector-based malaria control programmes in Cameroon. As part of ongoing resistance surveillance efforts, Anopheles gambiae s.l. female mosquitoes were exposed to organochlorine (DDT), a carbamate (bendiocarb), an organophosphate (malathion), and three pyrethroids (deltamethrin, lambda-cyhalothrin and permethrin) in WHO bioassay test kits. Results indicated a higher level of resistance (reduced mortality and knockdown effect) to DDT and pyrethroids in populations of A. gambiae s.s. than in A. arabiensis. The West and East African knockdown resistance (kdr) mutations were found in both species but at much higher frequencies in A. gambiae s.s. The West Africa kdr mutant was also more frequent in the A. gambiae S form than in the M form. No resistance to bendiocarb and malathion was found. Carbamate and organophosphorous compounds could thus be used as alternatives in locations in Cameroon where pyrethroid-resistant populations are found.
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