title: The spatial heterogeneity between Japanese encephalitis incidence distribution and environmental variables in Nepal.
abstract: BACKGROUND
  To identify potential environmental drivers of Japanese Encephalitis virus (JE) transmission in Nepal, we conducted an ecological study to determine the spatial association between 2005 Nepal JE incidence, and climate, agricultural, and land-cover variables at district level.
  
  
  METHODS
  District-level data on JE cases were examined using Local Indicators of Spatial Association (LISA) analysis to identify spatial clusters from 2004 to 2008 and 2005 data was used to fit a spatial lag regression model with climate, agriculture and land-cover variables.
  
  
  RESULTS
  Prior to 2006, there was a single large cluster of JE cases located in the Far-West and Mid-West terai regions of Nepal. After 2005, the distribution of JE cases in Nepal shifted with clusters found in the central hill areas. JE incidence during the 2005 epidemic had a stronger association with May mean monthly temperature and April mean monthly total precipitation compared to mean annual temperature and precipitation. A parsimonious spatial lag regression model revealed, 1) a significant negative relationship between JE incidence and April precipitation, 2) a significant positive relationship between JE incidence and percentage of irrigated land 3) a non-significant negative relationship between JE incidence and percentage of grassland cover, and 4) a unimodal non-significant relationship between JE Incidence and pig-to-human ratio.
  
  
  CONCLUSIONS
  JE cases clustered in the terai prior to 2006 where it seemed to shift to the Kathmandu region in subsequent years. The spatial pattern of JE cases during the 2005 epidemic in Nepal was significantly associated with low precipitation and the percentage of irrigated land. Despite the availability of an effective vaccine, it is still important to understand environmental drivers of JEV transmission since the enzootic cycle of JEV transmission is not likely to be totally interrupted. Understanding the spatial dynamics of JE risk factors may be useful in providing important information to the Nepal immunization program.
authors.affiliation: LUCINDA Group, Department of Epidemiology and Population Health, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, Cheshire, United Kingdom. d.impoinvil@liverpool.ac.uk
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Impoinvil
authors.forename: Tom
authors.initials: T
authors.lastname: Solomon
authors.forename: W William
authors.initials: WW
authors.lastname: Schluter
authors.forename: Ajit
authors.initials: A
authors.lastname: Rayamajhi
authors.forename: Ram Padarath
authors.initials: RP
authors.lastname: Bichha
authors.forename: Geeta
authors.initials: G
authors.lastname: Shakya
authors.forename: Cyril
authors.initials: C
authors.lastname: Caminade
authors.forename: Matthew
authors.initials: M
authors.lastname: Baylis
mesh_terms: D000383:Agriculture; D016000:Cluster Analysis; D004672:Encephalitis, Japanese / Q000453:epidemiology* / Q000635:transmission; D004777:Environment; D006801:Humans; D015994:Incidence; D008954:Models, Biological; D009390:Nepal / Q000453:epidemiology; D011891:Rain; D012621:Seasons; D013696:Temperature; D013997:Time Factors