title: Efficacy of indoor residual spraying with dichlorodiphenyltrichloroethane against malaria in Gambian communities with high usage of long-lasting insecticidal mosquito nets: a cluster-randomised controlled trial.
abstract: BACKGROUND
  Although many malaria control programmes in sub-Saharan Africa use indoor residual spraying with long-lasting insecticidal nets (LLINs), the two studies assessing the benefit of the combination of these two interventions gave conflicting results. We aimed to assess whether the addition of indoor residual spraying to LLINs provided a significantly different level of protection against clinical malaria in children or against house entry by vector mosquitoes.
  
  
  METHODS
  In this two-arm cluster, randomised, controlled efficacy trial we randomly allocated clusters of Gambian villages using a computerised algorithm to LLINs alone (n=35) or indoor residual spraying with dichlorodiphenyltrichloroethane plus LLINs (n=35). In each cluster, 65-213 children, aged 6 months to 14 years, were surveyed at the start of the 2010 transmission season and followed in 2010 and 2011 by passive case detection for clinical malaria. Exposure to parasite transmission was assessed by collection of vector mosquitoes with both light and exit traps indoors. Primary endpoints were the incidence of clinical malaria assessed by passive case detection and number of Anopheles gambiae sensu lato mosquitoes collected per light trap per night. Intervention teams had no role in data collection and the data collection teams were not informed of the spray status of villages. The trial is registered at the ISRCTN registry, number ISRCTN01738840.
  
  
  RESULTS
  LLIN coverage in 2011 was 3510 (93%) of 3777 children in the indoor residual spraying plus LLIN group and 3622 (95.5%) of 3791 in the LLIN group. In 2010, 7845 children were enrolled, 7829 completed passive case detection, and 7697 (98%) had complete clinical and covariate data. In 2011, 7009 children remained in the study, 648 more were enrolled, 7657 completed passive case detection, and 7545 (98.5%) had complete data. Indoor residual spraying coverage per cluster was more than 80% for both years in the indoor residual spraying plus LLIN group. Incidence of clinical malaria was 0.047 per child-month at risk in the LLIN group and 0.044 per child-month at risk in the indoor residual spraying plus LLIN group in 2010, and 0.032 per child-month at risk in the LLIN group and 0.034 per child-month at risk in the indoor residual spraying plus LLIN group in 2011. The incident rate ratio was 1.08 (95% CI 0.80-1.46) controlling for confounders and cluster by mixed-effect negative binomial regression on all malaria attacks for both years. No significant difference was recorded in the density of vector mosquitoes caught in light traps in houses over the two transmission seasons; the mean number of A gambiae sensu lato mosquitoes per trap per night was 6.7 (4.0-10.1) in the LLIN group and 4.5 (2.4-7.4) in the indoor residual spraying plus LLIN group (p=0.281 in the random-effects linear regression model).
  
  
  CONCLUSIONS
  We identified no significant difference in clinical malaria or vector density between study groups. In this area with high LLIN coverage, moderate seasonal transmission, and susceptible vectors, indoor residual spraying did not provide additional benefit.
  
  
  BACKGROUND
  UK Medical Research Council.
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia; London School of Hygiene and Tropical Medicine, London, UK; Durham University, Durham, UK.
authors.forename: Margaret
authors.initials: M
authors.lastname: Pinder
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Musa
authors.initials: M
authors.lastname: Jawara
authors.affiliation: National Malaria Control Programme, Banjul, The Gambia.
authors.forename: Lamin B S
authors.initials: LB
authors.lastname: Jarju
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Kolawole
authors.initials: K
authors.lastname: Salami
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: David
authors.initials: D
authors.lastname: Jeffries
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Majidah
authors.initials: M
authors.lastname: Adiamoh
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Kalifa
authors.initials: K
authors.lastname: Bojang
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Simon
authors.initials: S
authors.lastname: Correa
authors.affiliation: National Malaria Control Programme, Banjul, The Gambia.
authors.forename: Balla
authors.initials: B
authors.lastname: Kandeh
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Harparkash
authors.initials: H
authors.lastname: Kaur
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia; London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Conway
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia; Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: Umberto
authors.initials: U
authors.lastname: D'Alessandro
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK; Durham University, Durham, UK. Electronic address: s.w.lindsay@durham.ac.uk.
authors.forename: Steve W
authors.initials: SW
authors.lastname: Lindsay
mesh_terms: D000293:Adolescent; D000465:Algorithms; D000818:Animals; D000852:Anopheles / Q000187:drug effects; D002648:Child; D002675:Child, Preschool; D003633:Dichlorodiphenyl Dichloroethylene / Q000008:administration & dosage*; D005260:Female; D005714:Gambia; D006801:Humans; D007223:Infant; D057148:Insecticide-Treated Bednets; D007306:Insecticides / Q000008:administration & dosage*; D008288:Malaria / Q000517:prevention & control* / Q000635:transmission; D008297:Male; D009032:Mosquito Control / Q000379:methods
chemical_list: D007306:Insecticides; D003633:Dichlorodiphenyl Dichloroethylene