Environmental risk factors for equine West Nile virus disease cases in Texas
West Nile Virus (WNV) was first detected in the Texas equine population during June 2002. Infection has since spread rapidly across the state and become endemic in the equine population. Environmental risk factors associated with equine WNV attack rates in Texas counties during the period 2002 to 2004 were investigated. Equine WNV attack rates were smoothed using an empirical Bayesian model, because of the variability among county equine populations (range 46−9,517). Risk factors investigated included hydrological features (lakes, rivers, swamps, canals and river basins), land cover (tree, mosaic, shrub, herbaceous, cultivated and artificial), elevation, climate (rainfall and temperature), and reports of WNV-positive mosquito and wild bird samples. Estimated county equine WNV attack rate was best described by the number of lakes, presence of broadleaf deciduous forest, presence of cultivated areas, location within the Brazos River watershed, WNV-positive mosquito status and average temperature. An understanding of environmental factors that increase equine WNV disease risk can be used to design and target disease control programs.
KeywordsWest Nile virus Equine Spatial epidemiology GIS Risk factors Texas
- Anselin, L., 2005. Exploring Spatial Data with GeoDa™: A Workbook. University of Illinois, Urbana-Champaign. Available at http://sal.uiuc.edu/. Accessed 9 January 2008.
- Apperson, C. S., Hassan, H. K., Harrison, B. A., Savage, H. M., Aspen, S. E., Farajollahi, A., Crans, W., Daniels, T. J., Falco, R. C., Benedict, M., Anderson, M., McMillen, L., Unnasch T. R., 2004. Host feeding patterns of established and potential mosquito vectors of West Nile virus in the Eastern United States. Vector Borne and Zoonotic Diseases, 4, 45–72. doi:10.1089/153036604773083013 Google Scholar
- Blitvich, B. J., Fernandez-Salas, I., Contreras-Cordero, J. F., Merlenee, N. L., Gonzalez- Rojas, J. I., Komar, N., Gubler, D. J., Calisher, C. H., Beaty B. J., 2003. Serologic evidence of West Nile virus infection in horses, Coahuila State, Mexico. Emerging Infectious Diseases, 9, 20–27.Google Scholar
- Centers for Disease Control and Prevention, 2002. Provisional survelliance summary of the West Nile Virus epidemic – United States. Morbidity Mortality Weekly Reports, 51, 1129–1133.Google Scholar
- Hassan, A. N., Onsi, H. M., 2004. Remote sensing as a Tool for Mapping Mosquito Breeding Habitats and Associated Health Risk to Assist Control Efforts and Development Plans: A Case Study in Wadi El Natroun, Egypt. Journal of the Egyptian Society of Parasitology, 34, 367–382.Google Scholar
- Hayes, C. G., 1988. West Nile fever. The arboviruses: epidemiology and ecology. Volume 1, number 2, pp. 59–88.Google Scholar
- Komar, N., 2002. West Nile virus: epidemiology and ecology in North America. Advances in Virus Research, 61, 185–234.Google Scholar
- Leblond, A., Zientara, S., Chadoeuf, J., Comby, N., Heng, M. A., Sabatier, P., 2005. Prevalence of West Nile Virus infection in horses in the Camargue area, South of France (2001). Revue de Medecine Veterinaire, 156, 77−84.Google Scholar
- Leblond, A., Sandoz, A., Lefebvre, G., Zeller, H., Bicout, D. J., 2007. Remote sensing based identification of environmental risk factors associated with West Nile disease in horses in Camargue, France. Preventive Veterinary Medicine, 79, 20−31. doi:10.1016/j.prevetmed.2006.11.008 PubMedCrossRefGoogle Scholar
- Molaei, G., Andreadis, T. G., 2006. Identification of avian- and mammalian-derived bloodmeals in Aedes vexans and Culiseta melanura (Diptera: Culicidae) and its implication for West Nile virus transmission in Connecticut, U.S.A. Journal of Medical Entomology, 43, 1088−1093. doi:10.1603/0022-2585(2006)43[1088:IOAAMB]2.0.CO;2 PubMedCrossRefGoogle Scholar
- Ostlund, E.N., Andresen, J.E., Andresen, M., 2000. West Nile encephalitis. Veterinary Clinics of North America Equine Practice, 6, 427–441.Google Scholar
- Romi, R., Pontuale, G., Clufolini, M. G., Fiorentinin, G., Marchi, A., Nicoletti, L., Cocchi, M., Tamburro, A., 2004. Potential vectors of West Nile virus following and equine disease outbreak in Italy. Medical and Veterinary Entomology, 18, 202–224. doi:10.1111/j.1365-2915.2004.0478.x CrossRefGoogle Scholar