title: Associations between urbanicity and malaria at local scales in Uganda.
abstract: BACKGROUND
  Sub-Saharan Africa is expected to show the greatest rates of urbanization over the next 50 years. Urbanization has shown a substantial impact in reducing malaria transmission due to multiple factors, including unfavourable habitats for Anopheles mosquitoes, generally healthier human populations, better access to healthcare, and higher housing standards. Statistical relationships have been explored at global and local scales, but generally only examining the effects of urbanization on single malaria metrics. In this study, associations between multiple measures of urbanization and a variety of malaria metrics were estimated at local scales.
  
  
  METHODS
  Cohorts of children and adults from 100 households across each of three contrasting sub-counties of Uganda (Walukuba, Nagongera and Kihihi) were followed for 24 months. Measures of urbanicity included density of surrounding households, vegetation index, satellite-derived night-time lights, land cover, and a composite urbanicity score. Malaria metrics included the household density of mosquitoes (number of female Anopheles mosquitoes captured), parasite prevalence and malaria incidence. Associations between measures of urbanicity and malaria metrics were made using negative binomial and logistic regression models.
  
  
  RESULTS
  One site (Walukuba) had significantly higher urbanicity measures compared to the two rural sites. In Walukuba, all individual measures of higher urbanicity were significantly associated with a lower household density of mosquitoes. The higher composite urbanicity score in Walukuba was also associated with a lower household density of mosquitoes (incidence rate ratio = 0.28, 95 % CI 0.17-0.48, p < 0.001) and a lower parasite prevalence (odds ratio, OR = 0.44, CI 0.20-0.97, p = 0.04). In one rural site (Kihihi), only a higher density of surrounding households was associated with a lower parasite prevalence (OR = 0.15, CI 0.07-0.34, p < 0.001). And, in only one rural site (Nagongera) was living where NDVI ≤0.45 associated with higher incidence of malaria (IRR = 1.35, CI 1.35-1.70, p = 0.01).
  
  
  CONCLUSIONS
  Urbanicity has been shown previously to lead to a reduction in malaria transmission at large spatial scales. At finer scales, individual household measures of higher urbanicity were associated with lower mosquito densities and parasite prevalence only in the site that was generally characterized as being urban. The approaches outlined here can help better characterize urbanicity at the household level and improve targeting of control interventions.
authors.affiliation: Infectious Diseases Research Collaboration, Kampala, Uganda. skigozi@yahoo.com.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Kigozi
authors.affiliation: Clinton Health Access Initiative, Boston, USA. dpindolia@gmail.com.
authors.forename: Deepa K
authors.initials: DK
authors.lastname: Pindolia
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, USA. david.smith@zoo.ox.ac.uk.|Department of Zoology, University of Oxford, Oxford, UK. david.smith@zoo.ox.ac.uk.|Sanaria Institute for Global Health and Tropical Medicine, Rockville, MD, USA. david.smith@zoo.ox.ac.uk.
authors.forename: David L
authors.initials: DL
authors.lastname: Smith
authors.affiliation: Infectious Diseases Research Collaboration, Kampala, Uganda. emmy3md@yahoo.com.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Arinaitwe
authors.affiliation: Infectious Diseases Research Collaboration, Kampala, Uganda. agabaik@gmail.com.
authors.forename: Agaba
authors.initials: A
authors.lastname: Katureebe
authors.affiliation: Infectious Diseases Research Collaboration, Kampala, Uganda. kilamam@gmail.com.
authors.forename: Maxwell
authors.initials: M
authors.lastname: Kilama
authors.affiliation: Infectious Diseases Research Collaboration, Kampala, Uganda. jnankabirwa@yahoo.co.uk.
authors.forename: Joaniter
authors.initials: J
authors.lastname: Nankabirwa
authors.affiliation: School of Biological and Biomedical Sciences, Durham University, Durham, UK. s.w.lindsay@durham.ac.uk.
authors.forename: Steve W
authors.initials: SW
authors.lastname: Lindsay
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK. sarah.staedke@lshtm.ac.uk.
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Staedke
authors.affiliation: Department of Medicine, San Francisco General Hospital, University of California, San Francisco, CA, USA. gdorsey@medsfgh.ucsf.edu.
authors.forename: Grant
authors.initials: G
authors.lastname: Dorsey
authors.affiliation: Infectious Diseases Research Collaboration, Kampala, Uganda. mkamya@infocom.co.ug.|School of Medicine, Makerere University College of Health Sciences, Kampala, Uganda. mkamya@infocom.co.ug.
authors.forename: Moses R
authors.initials: MR
authors.lastname: Kamya
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, USA. A.J.Tatem@soton.ac.uk.|Department of Geography and Environment, University of Southampton, Southampton, UK. A.J.Tatem@soton.ac.uk.|Flowminder Foundation, Stockholm, Sweden. A.J.Tatem@soton.ac.uk.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Tatem
mesh_terms: D000328:Adult; D000818:Animals; D000852:Anopheles; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D040362:Geographic Information Systems; D006801:Humans; D015994:Incidence; D007223:Infant; D016778:Malaria, Falciparum / Q000453:epidemiology*; D010963:Plasmodium falciparum; D012111:Residence Characteristics / Q000706:statistics & numerical data*; D014454:Uganda / Q000453:epidemiology; D014505:Urban Population / Q000706:statistics & numerical data*