title: Impact of three years of large scale Indoor Residual Spraying (IRS) and Insecticide Treated Nets (ITNs) interventions on insecticide resistance in Anopheles gambiae s.l. in Benin.
abstract: BACKGROUND
  In Benin, Indoor Residual Spraying (IRS) and long-lasting insecticidal nets (LLINs) are the cornerstones of malaria prevention. In the context of high resistance of Anopheles gambiae to pyrethroids, The National Malaria Control Program (NMCP) has undertaken a full coverage of IRS in a no-flood zone in the Oueme region, coupled with the distribution of LLINs in a flood zone. We assessed the impact of this campaign on phenotypic resistance, kdr (knock-down resistance) and ace-1(R) (insensitive acetylcholinesterase) mutations.
  
  
  METHODS
  Insecticides used for malaria vector control interventions were bendiocarb WP (0.4 g/m²) and deltamethrin (55 mg/m²), respectively for IRS and LLINs. Susceptibility status of An. gambiae was assessed using World Health Organization bioassay tests to DDT, permethrin, deltamethrin and bendiocarb in the Oueme region before intervention (2007) and after interventions in 2008 and 2010. An. gambiae specimens were screened for identification of species, molecular M and S forms and for the detection of the West African kdr (L1014F) as well as ace-1(R) mutations using PCR techniques.
  
  
  RESULTS
  The univariate logistic regression performed showed that kdr frequency has increased significantly during the three years in the intervention area and in the control area. Several factors (LLINs, IRS, mosquito coils, aerosols, use of pesticides for crop protection) could explain the selection of individual resistant An. gambiae. The Kdr resistance gene could not be the only mechanism of resistance observed in the Oueme region. The high susceptibility to bendiocarb is in agreement with a previous study conducted in Benin. However, the occurrence of ace-1(R) heterozygous individuals even on sites far from IRS areas, suggests other factors may contribute to the selection of resistance other than those exerted by the vector control program.
  
  
  CONCLUSIONS
  The results of this study have confirmed that An.gambiae have maintained and developed the resistance to pyrethroids, but are still susceptible to bendiocarb. Our data clearly shows that selection of resistant individuals was caused by other insecticides than those used by the IRS and LLINs.
authors.affiliation: Faculté des Sciences et Techniques de l'Université d'Abomey Calavi, Calavi, Bénin. pagergil@yahoo.fr
authors.forename: Gil Germain
authors.initials: GG
authors.lastname: Padonou
authors.forename: Michel
authors.initials: M
authors.lastname: Sezonlin
authors.forename: Razaki
authors.initials: R
authors.lastname: Ossé
authors.forename: Nazaire
authors.initials: N
authors.lastname: Aizoun
authors.forename: Frédéric
authors.initials: F
authors.lastname: Oké-Agbo
authors.forename: Olivier
authors.initials: O
authors.lastname: Oussou
authors.forename: Ghélus
authors.initials: G
authors.lastname: Gbédjissi
authors.forename: Martin
authors.initials: M
authors.lastname: Akogbéto
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D001541:Benin; D004363:Drug Utilization / Q000706:statistics & numerical data*; D005260:Female; D019476:Insect Proteins / Q000235:genetics; D007305:Insecticide Resistance; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data*; D007306:Insecticides / Q000494:pharmacology*; D008288:Malaria / Q000517:prevention & control; D009032:Mosquito Control / Q000379:methods* / Q000706:statistics & numerical data*; D009570:Nitriles / Q000494:pharmacology; D048448:Phenylcarbamates / Q000494:pharmacology; D011722:Pyrethrins / Q000494:pharmacology; D016019:Survival Analysis
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D009570:Nitriles; D048448:Phenylcarbamates; D011722:Pyrethrins; C017180:decamethrin; C007725:bendiocarb