title: Insecticide resistance in disease vectors from Mayotte: an opportunity for integrated vector management.
abstract: BACKGROUND
  Mayotte, a small island in the Indian Ocean, has been affected for many years by vector-borne diseases. Malaria, Bancroftian filariasis, dengue, chikungunya and Rift Valley fever have circulated or still circulate on the island. They are all transmitted by Culicidae mosquitoes. To limit the impact of these diseases on human health, vector control has been implemented for more than 60 years on Mayotte. In this study, we assessed the resistance levels of four major vector species (Anopheles gambiae, Culex pipiens quinquefasciatus, Aedes aegypti and Aedes albopictus) to two types of insecticides: i) the locally currently-used insecticides (organophosphates, pyrethroids) and ii) alternative molecules that are promising for vector control and come from different insecticide families (bacterial toxins or insect growth regulators). When some resistance was found to one of these insecticides, we characterized the mechanisms involved.
  
  
  METHODS
  Larval and adult bioassays were used to evaluate the level of resistance. When resistance was found, we tested for the presence of metabolic resistance through detoxifying enzyme activity assays, or for target-site mutations through molecular identification of known resistance alleles.
  
  
  RESULTS
  Resistance to currently-used insecticides varied greatly between the four vector species. While no resistance to any insecticides was found in the two Aedes species, bioassays confirmed multiple resistance in Cx. p. quinquefasciatus (temephos: ~ 20 fold and deltamethrin: only 10% mortality after 24 hours). In An. gambiae, resistance was scarce: only a moderate resistance to temephos was found (~5 fold). This resistance appears to be due only to carboxyl-esterase overexpression and not to target modification. Finally, and comfortingly, none of the four species showed resistance to any of the new insecticides.
  
  
  CONCLUSIONS
  The low resistance observed in Mayotte's main disease vectors is particularly interesting, because it leaves a range of tools useable by vector control services. Together with the relative isolation of the island (thus limited immigration of mosquitoes), it provides us with a unique place to implement an integrated vector management plan, including all the good practices learned from previous experiences.
authors.affiliation: Institut de Recherche pour le Développement, Unité Mixte de Recherche MIVEGEC (IRD 224-CNRS 5290-UM1-UM2), 911, avenue Agropolis, BP 64501 34394 Montpellier cedex 5, France. nicolas.pocquet@ird.fr.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Pocquet
authors.forename: Frédéric
authors.initials: F
authors.lastname: Darriet
authors.forename: Betty
authors.initials: B
authors.lastname: Zumbo
authors.forename: Pascal
authors.initials: P
authors.lastname: Milesi
authors.forename: Julien
authors.initials: J
authors.lastname: Thiria
authors.forename: Vincent
authors.initials: V
authors.lastname: Bernard
authors.forename: Céline
authors.initials: C
authors.lastname: Toty
authors.forename: Pierrick
authors.initials: P
authors.lastname: Labbé
authors.forename: Fabrice
authors.initials: F
authors.lastname: Chandre
mesh_terms: D000818:Animals; D001681:Biological Assay; D017507:Comoros; D009033:Culicidae / Q000187:drug effects* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D007303:Insect Vectors / Q000187:drug effects*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D009032:Mosquito Control / Q000379:methods*
chemical_list: D007306:Insecticides