Insecticide resistance in Anopheles funestus (Diptera: Culicidae) from Mozambique

Malaria control in southern Mozambique is currently by indoor residual carbamate insecticide treatment, with pyrethroid-treated bed-nets distributed to pregnant women and children under five in northern Mozambique. The susceptibility of Anopheles funestus s.s. to pyrethroid, carbamate, organochlorine, and organophosphorus insecticides was determined by World Health Organization adult mosquito susceptibility tests at 19 localities in Mozambique, from March 2000 to July 2002. Biochemical assays were carried out on mosquitoes from the same families to detect shifts in the quantity or activity of enzyme families involved in insecticide detoxification. An. funestus from all localities remained fully susceptible to DDT and the organophosphorus insecticide malathion. A high level of pyrethroid resistance was detected in An. funestus populations in southern Mozambique. An. funestus outside Maputo province were still susceptible to pyrethroids. An. funestus from six localities also were resistant to carbamate insecticides propoxur and bendiocarb. Both pyrethroid and carbamate resistance occurred in five of these six localities. Mosquitoes from five of the localities with elevated p450 estimates, compared with the insecticide-susceptible Durban strain, were pyrethroid-resistant. The only exception to this trend was Mozal, which had elevated p450 estimates but full pyrethroid susceptibility by bioassay. The lack of cross-resistance between pyrethroids and DDT in Mozambican An. funestus suggests that a kdr-type target site resistance mechanism has not been selected. Low levels of insecticide-insensitive acetylcholinesterase, the target site for carbamates and organophosphates, were found in all populations tested. The high level of metabolically based pyrethroid resistance has implications for current malaria control programs in Mozambique.