Synergy between repellents and non-pyrethroid insecticides strongly extends the efficacy of treated nets against Anopheles gambiae.
BACKGROUND
To manage the kdr pyrethroid-resistance in Anopheline malaria vectors, new compounds or new strategies are urgently needed. Recently, mixing repellents (DEET) and a non-pyrethroid insecticide (propoxur) was shown to be as effective as deltamethrin, a standard pyrethroid, under laboratory conditions, because of a strong synergy between the two compounds. In the present study, the interactions between two repellents (DEET and KBR 3023) and a non-pyrethroid insecticide (pyrimiphos methyl or PM) on netting were investigated. The residual efficacy and the inhibition of blood feeding conferred by these mixtures were assessed against Anopheles gambiae mosquitoes.


METHODS
DEET and KBR 3023 were mixed with pyrimiphos methyl (PM), a organophosphate (OP) insecticide. The performance of mono- and bi-impregnated nets against adult mosquitoes was assessed using a miniaturized, experimental hut system (laboratory tunnel tests) that allows expression of behavioural responses to insecticide, particularly the mortality and blood feeding effects.


RESULTS
Both mixtures (PM+DEET and PM+KBR3023) induced 95% mortality for more than two months compared with less than one week for each compound used alone, then reflecting a strong synergy between the repellents and PM. A similar trend was observed with the blood feeding rates, which were significantly lower for the mixtures than for each component alone.


CONCLUSIONS
Synergistic interactions between organophosphates and repellents may be of great interest for vector control as they may contribute to increase the residual life of impregnated materials and improve the control of pyrethroid-resistance mosquitoes. These results prompt the need to evaluate the efficacy of repellent/non-pyrethroid insecticide mixtures against field populations of An. gambiae showing high level of resistance to Ops and pyrethroids.
Pennetier
Cédric
C
Institut de Recherche pour le Développement, Cotonou, Bénin. Cedric.Pennetier@ird.fr
Corbel
Vincent
V
Boko
Pélagie
P
Odjo
Abibatou
A
N'Guessan
Raphaël
R
Lapied
Bruno
B
Hougard
Jean-Marc
JM
D000818:Animals; D000852:Anopheles / Q000254:growth & development* / Q000469:parasitology; D001512:Bedding and Linens; D003671:DEET; D004357:Drug Synergism; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D007302:Insect Repellents; D007303:Insect Vectors / Q000254:growth & development* / Q000469:parasitology; D007306:Insecticides; D009032:Mosquito Control / Q000379:methods*; D010755:Organophosphates; D009946:Organothiophosphorus Compounds; D010880:Piperidines; D011722:Pyrethrins
D007302:Insect Repellents; D007306:Insecticides; D010755:Organophosphates; D009946:Organothiophosphorus Compounds; D010880:Piperidines; D011722:Pyrethrins; D003671:DEET; C014153:pirimiphos methyl; C483506:picaridin