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Krishna Thakur Hu Suk Lee

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Outline Introduction GIS questions? Objectives Materials and Methods Results Discussion Conclusions

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What 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)

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Transmission by Mosquitoes WNV is an Arbovirus transmitted by several mosquito species Most important vector: Culex spp. Mosquito abundance is associated with environmental and anthropogenic factors Standing Water Vegetation overgrowth Urbanization Host population (Humans and Horses)

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GIS question? Why some of the counties in Indiana State have high positive cases of mosquitoes for WNV compared with other counties?

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Objectives Use GIS to compare counties in Indiana in terms of high and low positive cases of WNV to Human population density Horse population density Percent of wetland Percent of urban Percent of different types of land uses Identify areas with high risk and make a risk map for WNV in Indiana using Ordinary least square regression model(OLS)

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Materials Data sources WNV mosquito cases by county in Indiana State in 2010 http://diseasemaps.usgs.gov/wnv_in_mosquito.html Indiana State map by county from Statewide danpatch.ecn.purdue.edu\asm540\data\tippecanoe\statewide Wetland Data http://inmap.indiana.edu/dload_page/hydrology.html Land cover danpatch.ecn.purdue.edu\asm540\data\tippecanoe\landcover

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Materials Data sources Human population (Census block) http://inmap.indiana.edu/dload_page/demographics.html Horse population http://www.ces.purdue.edu/extmedia/ID/ID-320-W.pdf Census urban Area danpatch.ecn.purdue.edu\asm540\data\tippecanoe\statewide Other related references

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Methods

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Normalization by area of county Human population Horse population Area of wetland Area of land use type Recombination and reclassification Forest= Deciduous + Evergreen + Mixed Wetland= Herbaceous + Woody

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Methods FINAL MODEL

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Methods Normalization by area of county Human population Horse population Wetland area Land cover values Reclassification and recombination of Land cover values Forest= Deciduous + Evergreen + Mixed Wetland= Woody wetland+ Emergent herbaceous wetland

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Initial Analysis

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Ordinary Least Square Regression Result

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Random spatial pattern of under and over prediction

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Real cases vs. Predicted cases

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Comparison of Counties with High and Low WNV

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Discussion WNV cases in mosquitoes are related with Human 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

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Discussion GIS OLS 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

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Conclusion Required 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

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Thank you for your attention