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Author Ward, M.P.; Ramsay, B.H.; Gallo, K.
Title Rural cases of equine West Nile virus encephalomyelitis and the normalized difference vegetation index Type Journal Article
Year 2005 Publication Vector Borne and Zoonotic Diseases (Larchmont, N.Y.) Abbreviated Journal Vector Borne Zoonotic Dis
Volume 5 Issue 2 Pages 181-188
Keywords Animals; Biomass; Cluster Analysis; Disease Outbreaks/veterinary; Ecology; *Geographic Information Systems; Horse Diseases/*epidemiology; Horses; Indiana/epidemiology; Plants; Population Surveillance; Rural Health; Seasons; Topography, Medical/*methods; West Nile Fever/epidemiology/*veterinary
Abstract Data from an outbreak (August to October, 2002) of West Nile virus (WNV) encephalomyelitis in a population of horses located in northern Indiana was scanned for clusters in time and space. One significant (p = 0.04) cluster of case premises was detected, occurring between September 4 and 10 in the south-west part of the study area (85.70 degrees N, 45.50 degrees W). It included 10 case premises (3.67 case premises expected) within a radius of 2264 m. Image data were acquired by the Advanced Very High Resolution Radiometer (AVHRR) sensor onboard a National Oceanic and Atmospheric Administration polar-orbiting satellite. The Normalized Difference Vegetation Index (NDVI) was calculated from visible and near-infrared data of daily observations, which were composited to produce a weekly-1km(2) resolution raster image product. During the epidemic, a significant (p < 0.01) decrease (0.025 per week) in estimated NDVI was observed at all case and control premise sites. The median estimated NDVI (0.659) for case premises within the cluster identified was significantly (p < 0.01) greater than the median estimated NDVI for other case (0.571) and control (0.596) premises during the same period. The difference in median estimated NDVI for case premises within this cluster, compared to cases not included in this cluster, was greatest (5.3% and 5.1%, respectively) at 1 and 5 weeks preceding occurrence of the cluster. The NDVI may be useful for identifying foci of WNV transmission.
Address Department of Veterinary Pathobiology, Purdue University School of Veterinary Medicine, West Lafayette, Indiana, USA. mward@cvm.tamu.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1530-3667 ISBN Medium
Area Expedition Conference
Notes PMID:16011435 Approved no
Call Number Equine Behaviour @ team @ Serial 2627
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