title: The relative contribution of climate variability and vector control coverage to changes in malaria parasite prevalence in Zambia 2006-2012.
abstract: Four malaria indicator surveys (MIS) were conducted in Zambia between 2006 and 2012 to evaluate malaria control scale-up. Nationally, coverage of insecticide-treated nets (ITNs) and indoor residual spraying (IRS) increased over this period, while parasite prevalence in children 1-59 months decreased dramatically between 2006 and 2008, but then increased from 2008 to 2010. We assessed the relative effects of vector control coverage and climate variability on malaria parasite prevalence over this period.
  
  
  
  Nationally-representative MISs were conducted in April-June of 2006, 2008, 2010 and 2012 to collect household-level information on malaria control interventions such as IRS, ITN ownership and use, and child parasite prevalence by microscopic examination of blood smears. We fitted Bayesian geostatistical models to assess the association between IRS and ITN coverage and climate variability and malaria parasite prevalence. We created predictions of the spatial distribution of malaria prevalence at each time point and compared results of varying IRS, ITN, and climate inputs to assess their relative contributions to changes in prevalence.
  
  
  
  Nationally, the proportion of households owning an ITN increased from 37.8 % in 2006 to 64.3 % in 2010 and 68.1 % in 2012, with substantial heterogeneity sub-nationally. The population-adjusted predicted child malaria parasite prevalence decreased from 19.6 % in 2006 to 10.4 % in 2008, but rose to 15.3 % in 2010 and 13.5 % in 2012. We estimated that the majority of this prevalence increase at the national level between 2008 and 2010 was due to climate effects on transmission, although there was substantial heterogeneity at the provincial level in the relative contribution of changing climate and ITN availability. We predict that if climate factors preceding the 2010 survey were the same as in 2008, the population-adjusted prevalence would have fallen to 9.9 % nationally.
  
  
  
  These results suggest that a combination of climate factors and reduced intervention coverage in parts of the country contributed to both the reduction and rebound in malaria parasite prevalence. Unusual rainfall patterns, perhaps related to moderate El Niño conditions, may have contributed to this variation. Zambia has demonstrated considerable success in scaling up vector control. This analysis highlights the importance of accounting for climate variability when using cross-sectional data for evaluation of malaria control efforts.
authors: Malaria Elimination Initiative, Global Health Group, University of California, 500 16th St, San Francisco, CA, 94158, USA. bennetta@globalhealth.ucsf.edu.|Center for Applied Malaria Research and Evaluation, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA. bennetta@globalhealth.ucsf.edu.
authors: Adam
authors: A
authors: Bennett
authors: Center for Applied Malaria Research and Evaluation, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA.
authors: Josh
authors: J
authors: Yukich
authors: PATH Malaria Control and Evaluation Partnership in Africa (MACEPA), Lusaka, Zambia.
authors: John M
authors: JM
authors: Miller
authors: Center for Applied Malaria Research and Evaluation, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA.
authors: Joseph
authors: J
authors: Keating
authors: National Malaria Control Centre, Ministry of Health, Lusaka, Zambia.
authors: Hawela
authors: H
authors: Moonga
authors: National Malaria Control Centre, Ministry of Health, Lusaka, Zambia.
authors: Busiku
authors: B
authors: Hamainza
authors: National Malaria Control Centre, Ministry of Health, Lusaka, Zambia.
authors: Mulakwa
authors: M
authors: Kamuliwo
authors: Malaria Elimination Initiative, Global Health Group, University of California, 500 16th St, San Francisco, CA, 94158, USA.
authors: Ricardo
authors: R
authors: Andrade-Pacheco
authors: Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors: Penelope
authors: P
authors: Vounatsou
authors: PATH Malaria Control and Evaluation Partnership in Africa (MACEPA), Lusaka, Zambia.
authors: Richard W
authors: RW
authors: Steketee
authors: Center for Applied Malaria Research and Evaluation, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA.
authors: Thomas P
authors: TP
authors: Eisele
mesh_terms: D000818:Animals; D002675:Child, Preschool; D057231:Climate Change; D009033:Culicidae / Q000187:drug effects / Q000469:parasitology / Q000502:physiology*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007223:Infant; D007303:Insect Vectors / Q000187:drug effects / Q000469:parasitology / Q000502:physiology*; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data; D007306:Insecticides / Q000494:pharmacology; D008288:Malaria / Q000453:epidemiology* / Q000469:parasitology / Q000517:prevention & control / Q000635:transmission*; D008297:Male; D009032:Mosquito Control; D015995:Prevalence; D015024:Zambia / Q000453:epidemiology
chemical_list: D007306:Insecticides
keywords: Climate; Geostatistics; Malaria; Vector control