University of Saskatchewan

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Tasha Epp (Photo by Liam Richards)
August 28, 2006

Graduate student developing tool to predict West Nile risk in Sask.

Monday, August 28, 2006

(>Third in a Series)

By David Hutton

For The StarPhoenix

A University of Saskatchewan graduate student is developing a cutting-edge model that will predict the risk of West Nile virus in Saskatchewan -- a tool that could help curb future outbreaks and focus education and vaccination efforts in the province.

Combining data from a massive 2003 provincial survey of horses potentially exposed to West Nile virus with environmental and climate data collected from specialized NASA satellites, U of S epidemiology PhD student Tasha Epp is developing a predictive map for the risk of infection with West Nile virus in Saskatchewan.

"By gaining a better understanding of where the risk of infection is diminished or elevated, we can identify specific areas in Saskatchewan where surveillance and vaccination programs are needed for the West Nile virus," says Epp.

"This information will help to predict the risk of infection in future seasons and determine ways to consolidate surveillance and public education programs."

Working with researchers in the Western College of Veterinary Medicine (WCVM) and travelling throughout remote regions of Saskatchewan in the summer of 2003, Epp and a master's student, Rebecca Corrigan, collected blood samples from more than 1,100 horses, in hopes of answering questions pertaining to the risk of West Nile for horses.

West Nile is a virus of wild birds, transmitted from bird to bird primarily by mosquitoes. Native to southern Europe, the Middle East and Africa, the virus arrived in North America in 1999 and quickly spread across the continent.

In mild human cases, symptoms may include flu-like complaints -- fever, headache, mild rashes or swollen glands. For every five people infected with West Nile, one has a mild illness usually lasting three to six days. Meningitis (inflammation of the lining of the brain or spinal cord) or encephalitis (brain inflammation) develops in about one in 150 people infected with West Nile.

Birds, horses and humans are particularly sensitive to the virus. Like humans, most horses infected with West Nile virus are successful in fighting the infection and do not develop symptoms. Horses that do develop clinical signs may show anything from slight hypersensitivity and an unsteady gait to severe paralysis and death.

Because horses are at a similar risk of infection as humans and reside in the same areas, tracking infection among them can anticipate human risk.

Epp's early analysis of the 2003 study identified the southern portion of the province (from Maple Creek to Estevan) as a hot spot and the central portion of the province (from Meadow Lake to Prince Albert) as relatively low risk.

But the goal of Epp's research is not only to show where the disease is occurring most in the province but also why it is occurring there -- a question she is relying on specialized NASA climate satellite data to answer.

"Satellite observations are a new method of climate data collection due to their wide coverage and accessibility," says Epp. "Satellite data serves as an important source of continuous global information that helps monitor disease outbreaks."

Using a similar methodology to malaria research in Africa, Epp is using the satellite data to look for areas of ideal environmental conditions and compare these with what she already knows about the distribution of the virus infection in horses in the province.

Epp, who is supervised by Cheryl Waldner in the department of large animal clinical sciences, says she is sure to take into account other factors, such as land use and mosquito control programs, that also may contribute to regional variation in the incidence of disease.

Although her results are currently in their preliminary phase, Epp says hot and dry conditions on the Prairies are conducive to the spread of the West Nile virus, which explains the high incidence of West Nile in southern Saskatchewan.

The hope is that Epp's research will aid in efforts to develop an early-warning system for potential West Nile outbreaks.

"This information will be used for the purpose of modelling and creating predictive risk maps of risk of infection with West Nile virus," says Epp.

"If successful, these maps could be useful for both horses and humans and updated on a yearly basis."

She also hopes researchers can use this project as a useful model to develop surveillance and predictive modelling programs for other emerging diseases that potentially affect livestock and humans.

Although there is a new, federally approved vaccine for horses, there is currently no licensed human vaccine. Epp's research has provided evidence the killed vaccine is effective in prevention of clinical disease in horses.

Funding for the study is provided by the WCVM Equine Health Research Fund, Wyeth Animal Health, Saskatchewan Health and Saskatchewan Agriculture, Food and Rural Revitalization. Epp and Corrigan received research fellowships from WCVM's Interprovincial Graduate Student Fellowship Fund.

(This article is part of a partnership initiative between The StarPhoenix and University of Saskatchewan Research Communications Office to highlight the work of student researchers and showcase the efforts of student writers and photographers.)

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