title: What Is Threatening the Effectiveness of Insecticide-Treated Bednets? A Case-Control Study of Environmental, Behavioral, and Physical Factors Associated with Prevention Failure.
abstract: BACKGROUND
  Insecticide-treated nets are the cornerstone of global malaria control and have been shown to reduce malaria morbidity by 50-60%. However, some areas are experiencing a resurgence in malaria following successful control. We describe an efficacy decay framework to understand why high malaria burden persists even under high ITN coverage in a community in western Kenya.
  
  
  METHODS
  We enrolled 442 children hospitalized with malaria and paired them with age, time, village and gender-matched controls. We completed comprehensive household and neighborhood assessments including entomological surveillance. The indicators are grouped into five domains in an efficacy decay framework: ITN ownership, compliance, physical integrity, vector susceptibility and facilitating factors. After variable selection, case-control data were analyzed using conditional logistic regression models and mosquito data were analyzed using negative binomial regression. Predictive margins were calculated from logistic regression models.
  
  
  RESULTS
  Measures of ITN coverage and physical integrity were not correlated with hospitalized malaria in our study. However, consistent ITN use (Adjusted Odds Ratio (AOR) = 0.23, 95%CI: 0.12-0.43), presence of nearby larval sites (AOR = 1.137, 95%CI: 1.02-1.27), and specific types of crops (AOR (grains) = 0.446, 95%CI: 0.24-0.82) were significantly correlated with malaria amongst children who owned an ITN. The odds of hospitalization for febrile malaria nearly tripled when one other household member had symptomatic malaria infection (AOR-2.76, 95%CI:1.83-4.18). Overall, perfect household adherence could reduce the probability of hospitalization for malaria to less than 30% (95%CI:0.12-0.46) and adjusting environmental factors such as elimination of larval sites and growing grains nearby could reduce the probability of hospitalization for malaria to less than 20% (95%CI:0.04-0.31).
  
  
  CONCLUSIONS
  Availability of ITNs is not the bottleneck for malaria prevention in this community. Behavior change interventions to improve compliance and environmental management of mosquito breeding habitats may greatly enhance ITN efficacy. A better understanding of the relationship between agriculture and mosquito survival and feeding success is needed.
authors.affiliation: College of Health Sciences, Moi University, Eldoret, Kenya.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Obala
authors.affiliation: College of Health Sciences, Moi University, Eldoret, Kenya.
authors.forename: Judith Nekesa
authors.initials: JN
authors.lastname: Mangeni
authors.affiliation: Duke Global Health Institute, Durham, North Carolina, United States of America.
authors.forename: Alyssa
authors.initials: A
authors.lastname: Platt
authors.affiliation: Academic Model Providing Access to Healthcare, Eldoret, Kenya.
authors.forename: Daniel
authors.initials: D
authors.lastname: Aswa
authors.affiliation: Academic Model Providing Access to Healthcare, Eldoret, Kenya.
authors.forename: Lucy
authors.initials: L
authors.lastname: Abel
authors.affiliation: Webuye Health and Demographic Surveillance System, Moi University, Eldoret, Kenya.
authors.forename: Jane
authors.initials: J
authors.lastname: Namae
authors.affiliation: College of Health Sciences, Moi University, Eldoret, Kenya; Duke Global Health Institute, Durham, North Carolina, United States of America; Department of Medicine, Duke University, Durham, North Carolina, United States of America.
authors.forename: Wendy
authors.initials: W
authors.lastname: Prudhomme O'Meara
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001947:Breeding; D016022:Case-Control Studies; D002675:Child, Preschool; D009033:Culicidae / Q000502:physiology; D004777:Environment; D005260:Female; D006297:Health Services Accessibility / Q000706:statistics & numerical data; D006801:Humans; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data*; D008288:Malaria / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D015397:Program Evaluation; D012307:Risk Factors