Reduced efficacy of insecticide-treated nets and indoor residual spraying for malaria control in pyrethroid resistance area, Benin.
The pyrethroid knockdown resistance gene (kdr) has become widespread in Anopheles gambiae in West Africa. A trial to test the continuing efficacy of insecticide-treated nets (ITN) and indoor residual spraying (IRS) was undertaken in experimental huts at 2 sites in Benin, the first where kdr is present at high frequency (Ladji), the second-where An. gambiae is susceptible (Malanville). Holes were made in the nets to mimic worn nets. At Malanville, 96% of susceptible An. gambiae were inhibited from blood-feeding, whereas at Ladji feeding was uninhibited by ITNs. The mortality rate of An. gambiae in ITN huts was 98% in Malanville but only 30% at Ladji. The efficacy of IRS was equally compromised. Mosquitoes at Ladji had higher oxidase and esterase activity than in a laboratory-susceptible strain, but this fact did not seem to contribute to resistance. Pyrethroid resistance in An. gambiae appears to threaten the future of ITN and IRS in Benin.
N'Guessan
Raphael
R
London School of Hygiene and Tropical Medicine, Cotonou, Benin, West Africa.
Corbel
Vincent
V
Akogbéto
Martin
M
Rowland
Mark
M
D000818:Animals; D000852:Anopheles / Q000187:drug effects; D001512:Bedding and Linens; D001541:Benin / Q000453:epidemiology; D003465:Culex / Q000187:drug effects; D006801:Humans; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology; D008288:Malaria / Q000517:prevention & control*; D009032:Mosquito Control / Q000379:methods*; D009570:Nitriles / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*
D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C037304:cyhalothrin