title: Efficacy of ICON® Maxx in the laboratory and against insecticide-resistant Anopheles gambiae in central Côte d'Ivoire.
abstract: BACKGROUND
  Long-lasting treatment kits, designed to transform untreated nets into long-lasting insecticidal nets (LLINs), may facilitate high coverage with LLINs where non-treated nets are in place. In this study, the efficacy of ICON® Maxx (Syngenta) was evaluated under laboratory conditions and in an experimental hut trial in central Côte d'Ivoire, where Anopheles gambiae s.s. are resistant to pyrethroid insecticides.
  
  
  METHODS
  In the laboratory, polyester and polyethylene net samples were treated with ICON® Maxx, washed up to 20 times and their efficacy determined in World Health Organization (WHO) cone assays against a susceptible laboratory An. gambiae s.s. colony. Over a 12-month period, the polyester nets were evaluated in a hut trial to determine mosquito deterrence, induced exophily, blood-feeding inhibition and mortality.
  
  
  RESULTS
  In the laboratory, ICON® Maxx-treated polyethylene nets showed higher efficacy against pyrethroid-susceptible mosquitoes than polyester nets. After 20 washings, insecticidal efficacy in bioassays was 59.4% knockdown (KD) and 22.3% mortality for polyethylene, and 55.3% KD and 17.9% mortality for polyester nets. In experimental huts, treated nets showed strong deterrence, induced exophily and an over three-fold reduction in blood-fed mosquitoes. More than half (61.8%) of the mosquitoes entering the huts with treated nets were found dead the next morning despite high levels of KD resistance. After washing the treated nets, KD and mortality rates were close to or exceeded predefined WHO thresholds in cone bioassays.
  
  
  CONCLUSIONS
  In contrast to previous laboratory investigation, ICON® Maxx-treated nets showed only moderate KD and mortality rates. However, under semi-field conditions, in an area where mosquitoes are resistant to pyrethroids, ICON® Maxx showed high deterrence, induced exophily and provided a significant reduction in blood-feeding rates; features that are likely to have a positive impact in reducing malaria transmission. The WHO cone test may not always be a good proxy for predicting product performance under field conditions.
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
authors.forename: Mirko S
authors.initials: MS
authors.lastname: Winkler
authors.forename: Emile
authors.initials: E
authors.lastname: Tchicaya
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Koudou
authors.forename: Jennifer
authors.initials: J
authors.lastname: Donzé
authors.forename: Christian
authors.initials: C
authors.lastname: Nsanzabana
authors.forename: Pie
authors.initials: P
authors.lastname: Müller
authors.forename: Akré M
authors.initials: AM
authors.lastname: Adja
authors.forename: Jürg
authors.initials: J
authors.lastname: Utzinger
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D001681:Biological Assay; D007560:Cote d'Ivoire; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D006801:Humans; D057148:Insecticide-Treated Bednets; D007306:Insecticides / Q000494:pharmacology*; D008297:Male; D009032:Mosquito Control / Q000379:methods; D016019:Survival Analysis; D055815:Young Adult
chemical_list: D007306:Insecticides