title: ITN mixtures of chlorfenapyr (Pyrrole) and alphacypermethrin (Pyrethroid) for control of pyrethroid resistant Anopheles arabiensis and Culex quinquefasciatus.
abstract: Pyrethroid resistant Anopheles gambiae malaria vectors are widespread throughout sub-Saharan Africa and continued efficacy of pyrethroid ITNs is under threat. Chlorfenapyr is a promising pyrrole insecticide with a unique mechanism of action conferring no cross-resistance to existing public health insecticides. Mixtures of chlorfenapyr (CFP) and alphacypermethrin (alpha) may provide additional benefits over chlorfenapyr or alphacypermethrin used alone. An ITN mixture of CFP 100 mg/m(2)+alpha 25 mg/m(2) was compared with CFP 100 mg/m(2) and alpha 25 mg/m(2) in a small-scale experimental hut trial in an area of wild An. arabiensis. The same treatments were evaluated in tunnel tests against insectary-reared pyrethroid susceptible and resistant Culex quinquefasciatus. Performance was measured in terms of insecticide-induced mortality, and blood-feeding inhibition. Tunnel tests showed that mixtures of CFP 100+ alpha 25 were 1.2 and 1.5 times more effective at killing susceptible Cx. quinquefasciatus than either Alpha 25 (P = 0.001) or CFP 100 (P = 0.001) ITNs. Mixtures of CFP100+ alpha 25 were 2.2 and 1.2 times more effective against resistant Cx. quinquefasciatus than either alpha 25 (P = 0.001) or CFP100 (P = 0.003) ITNs. CFP 100+ alpha 25 produced higher levels of blood-feeding inhibition than CFP alone for susceptible (94 vs 46%, P = 0.001) and resistant (84 vs 53%, P = 0.001) strains. In experimental huts the mixture of CFP 100+ Alpha 25 killed 58% of An. arabiensis, compared with 50% for alpha and 49% for CFP, though the differences were not significant. Blood-feeding inhibition was highest in the mixture with a 76% reduction compared to the untreated net (P = 0.001). ITN mixtures of chlorfenapyr and alphacypermethrin should restore effective control of resistant populations of An. gambiae malaria vectors, provide protection from blood-feeding, and may have benefits for resistance management, particularly in areas with low or moderate frequency of pyrethroid resistance. A wash-resistant mixture should be developed urgently.
authors: Department of Disease Control, London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom. Richard.Oxborough@lshtm.ac.uk
authors: Richard M
authors: RM
authors: Oxborough
authors: Jovin
authors: J
authors: Kitau
authors: Johnson
authors: J
authors: Matowo
authors: Emmanuel
authors: E
authors: Feston
authors: Rajab
authors: R
authors: Mndeme
authors: Franklin W
authors: FW
authors: Mosha
authors: Mark W
authors: MW
authors: Rowland
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D003465:Culex / Q000187:drug effects*; D004338:Drug Combinations; D005260:Female; D007305:Insecticide Resistance; D007306:Insecticides / Q000008:administration & dosage / Q000494:pharmacology*; D009032:Mosquito Control; D011722:Pyrethrins / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D004338:Drug Combinations; D007306:Insecticides; D011722:Pyrethrins; C017160:cypermethrin; C436643:chlorfenapyr