Spatial Risk Factors for West Nile Virus Positivity in Mosquitoes in Indiana State
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Transcript of Spatial Risk Factors for West Nile Virus Positivity in Mosquitoes in Indiana State
Spatial Risk Factors for West Nile Virus Positivity in Mosquitoes in Indiana
Spatial Risk Factors for West Nile Virus Positivity in Mosquitoes in Indiana StateKrishna ThakurHu Suk Lee
1OutlineIntroductionGIS questions?ObjectivesMaterials and MethodsResultsDiscussionConclusions
2What is WNV?West Nile virus (WNV) is a Flavivirus which causes neurological disease in humans, horses and other animals
Birds develop substantial viremia and are considered a major reservoir host
Humans and horses are dead-end hosts
WNV was first detected in 1999 in the United States (New York State)
3Transmission by MosquitoesWNV is an Arbovirus transmitted by several mosquito speciesMost important vector: Culex spp.
Mosquito abundance is associated with environmental and anthropogenic factorsStanding WaterVegetation overgrowthUrbanizationHost population (Humans and Horses)
4GIS question?Why some of the counties in Indiana State have high positive cases of mosquitoes for WNV compared with other counties?
5ObjectivesUse GIS to compare counties in Indiana in terms of high and low positive cases of WNV toHuman population densityHorse population densityPercent of wetlandPercent of urbanPercent of different types of land usesIdentify areas with high risk and make a risk map for WNV in Indiana using Ordinary least square regression model(OLS)
6MaterialsData sourcesWNV mosquito cases by county in Indiana State in 2010http://diseasemaps.usgs.gov/wnv_in_mosquito.html
Indiana State map by county from Statewidedanpatch.ecn.purdue.edu\asm540\data\tippecanoe\statewide
Wetland Datahttp://inmap.indiana.edu/dload_page/hydrology.html
Land coverdanpatch.ecn.purdue.edu\asm540\data\tippecanoe\landcover
7MaterialsData sourcesHuman population (Census block)http://inmap.indiana.edu/dload_page/demographics.html
Horse populationhttp://www.ces.purdue.edu/extmedia/ID/ID-320-W.pdf
Census urban Area danpatch.ecn.purdue.edu\asm540\data\tippecanoe\statewide
Other related references
8Methods
9MethodsNormalization by area of countyHuman populationHorse populationArea of wetlandArea of land use type
Recombination and reclassificationForest= Deciduous + Evergreen + MixedWetland= Herbaceous + Woody
10Methods
FINAL MODEL
11MethodsNormalization by area of county Human populationHorse populationWetland areaLand cover valuesReclassification and recombination of Land cover valuesForest= Deciduous + Evergreen + MixedWetland= Woody wetland+ Emergent herbaceous wetland
12Initial Analysis
13Initial Analysis
14Ordinary Least Square Regression Result
15Random spatial pattern of under and over prediction
16Real cases vs. Predicted cases
17Comparison of Counties with High and Low WNV
18DiscussionWNV cases in mosquitoes are related withHuman density
This model explains 28% of variation in WNV cases in mosquito indicating some variables are still missing in the model
Predicted cases are not spatially autocorrelated indicating random pattern and model significance
19DiscussionGISOLS tool and Spatial correlation tool work well in comparing and modeling multiple spatial factors
Good Visualization tool to understand the distribution of disease and associated risk factors
Useful to obtain spatial data for other studies
20ConclusionRequired more factors in order to explain the WNV cases in mosquito
Obtained data can be analyzed using robust statistical software
Helpful to design mosquito control program
Acquaintance with GIS application in spatial epidemiology
21Thank you for your attention
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