title: Impact of long-lasting, insecticidal nets on anaemia and prevalence of Plasmodium falciparum among children under five years in areas with highly resistant malaria vectors.
abstract: BACKGROUND
  The widespread use of insecticide-treated nets (LLINs) leads to the development of vector resistance to insecticide. This resistance can reduce the effectiveness of LLIN-based interventions and perhaps reverse progress in reducing malaria morbidity. To prevent such difficulty, it is important to know the real impact of resistance in the effectiveness of mosquito nets. Therefore, an assessment of LLIN efficacy was conducted in malaria prevention among children in high and low resistance areas.
  
  
  METHODS
  The study was conducted in four rural districts and included 32 villages categorized as low or high resistance areas in Plateau Department, south-western Benin. Larvae collection was conducted to measure vector susceptibility to deltamethrin and knockdown resistance (kdr) frequency. In each resistance area, around 500 children were selected to measure the prevalence of malaria infection as well as the prevalence of anaemia associated with the use of LLINs.
  
  
  RESULTS
  Observed mortalities of Anopheles gambiae s.s population exposed to deltamethrin ranged from 19 to 96%. Knockdown resistance frequency was between 38 and 84%. The prevalence of malaria infection in children under five years was 22.4% (19.9-25.1). This prevalence was 17.3% (14.2-20.9) in areas of high resistance and 27.1% (23.5-31.1) in areas of low resistance (p=0.04). Eight on ten children that were aged six - 30 months against seven on ten of those aged 31-59 months were anaemic. The anaemia observed in the six to 30-month old children was significantly higher than in the 31-59 month old children (p=0.00) but no difference associated with resistance areas was observed (p=0.35). The net use rate was 71%. The risk of having malaria was significantly reduced (p<0.05) with LLIN use in both low and high resistance areas. The preventive effect of LLINs in high resistance areas was 60% (95% CI: 40-70), and was significantly higher than that observed in low resistance areas (p<0.05).
  
  
  CONCLUSIONS
  The results of this study showed that the resistance of malaria vectors seems to date not have affected the impact of LLINs and the use of LLINs was highly associated with reduced malaria prevalence irrespective of resistance.
authors.affiliation: National Malaria Control Programme, Cotonou, Benin. filemont@yahoo.fr.
authors.forename: Filémon T
authors.initials: FT
authors.lastname: Tokponnon
authors.forename: Aurore Hounto
authors.initials: AH
authors.lastname: Ogouyémi
authors.forename: Yolande
authors.initials: Y
authors.lastname: Sissinto
authors.forename: Arthur
authors.initials: A
authors.lastname: Sovi
authors.forename: Virgile
authors.initials: V
authors.lastname: Gnanguenon
authors.forename: Sylvie
authors.initials: S
authors.lastname: Cornélie
authors.forename: Adicath Adéola
authors.initials: AA
authors.lastname: Adéothy
authors.forename: Razaki
authors.initials: R
authors.lastname: Ossè
authors.forename: Abel
authors.initials: A
authors.lastname: Wakpo
authors.forename: Dina
authors.initials: D
authors.lastname: Gbénou
authors.forename: Mariam
authors.initials: M
authors.lastname: Oke
authors.forename: Dorothée
authors.initials: D
authors.lastname: Kinde-Gazard
authors.forename: Immo
authors.initials: I
authors.lastname: Kleinschmidt
authors.forename: Martin C
authors.initials: MC
authors.lastname: Akogbeto
authors.forename: Achille
authors.initials: A
authors.lastname: Massougbodji
mesh_terms: D000328:Adult; D000740:Anemia / Q000453:epidemiology / Q000517:prevention & control*; D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D001541:Benin / Q000453:epidemiology; D001681:Biological Assay; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007305:Insecticide Resistance; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data*; D007306:Insecticides / Q000494:pharmacology; D007814:Larva / Q000187:drug effects; D016778:Malaria, Falciparum / Q000150:complications / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D009570:Nitriles / Q000494:pharmacology; D011247:Pregnancy; D015995:Prevalence; D011722:Pyrethrins / Q000494:pharmacology; D012424:Rural Population; D016019:Survival Analysis
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin