Research

Multi-function oxidases are responsible for the synergistic interactions occurring between repellents and insecticides in mosquitoes

Julien Bonnet¹ , Cédric Pennetier^1,4,5 , Stéphane Duchon¹ , Bruno Lapied³ and Vincent Corbel²

¹  Laboratoire de Lutte contre les Insectes Nuisibles, Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP 64 501, 34394 Montpellier, France

²  Centre de Recherches Entomologiques de Cotonou (CREC), Institut de Recherche pour le Développement (IRD), 01 BP 4414 RP, Cotonou, Benin

³  Laboratoire RCIM UPRES EA 2647/USC INRA 2023, IFR 149 QUASAV, 49045 Angers, cedex, France

⁴  University of Greenwich at Medway, Central Avenue, Chatham, Kent ME4 4TB, England, UK

⁵  School of Life Science, University of Sussex, Brighton, BN1 9QG, England, UK

author email corresponding author email

Parasites & Vectors 2009, 2:17doi:10.1186/1756-3305-2-17

Published:	16 April 2009

Abstract

Background

With the spread of pyrethroid resistance in mosquitoes, the combination of an insecticide (carbamate or organophosphate) with a repellent (DEET) is considered as a promising alternative strategy for the treatment of mosquito nets and other relevant materials. The efficacy of these mixtures comes from the fact that they reproduce pyrethroid features and that positive interactions occur between insecticides and repellent. To better understand the mechanisms involved and assess the impact of detoxifying enzymes (oxidases and esterases) in these interactions, bioassays were carried out in the laboratory against the main dengue vector Aedes aegypti.

Methods

Topical applications of DEET and propoxur (carbamate), used alone or as a mixture, were carried out on female mosquitoes, using inhibitors of the two main detoxification pathways in the insect. PBO, an inhibitor of multi-function oxidases, and DEF, an inhibitor of esterases, were applied one hour prior to the main treatment.

Results

Results showed that synergism between DEET and propoxur disappeared in the presence of PBO but not with DEF. This suggests that oxidases, contrary to esterases, play a key role in the interactions occurring between DEET and cholinesterase inhibitors in mosquitoes.

Conclusion

These findings are of great interest for the implementation of "combination nets" in the field. They support the need to combine insecticide with repellent to overcome insecticide resistance in mosquitoes of public health importance.