Crunching the Numbers: California's Equine WNV Mortality Rate

California horse owners have been keenly aware of the problem presented by West Nile virus (WNV) in 2004, but the problem took a deadly turn last year. The virus was discovered in all but one of the Golden State's 58 counties, leaving only Del Norte County without any reported cases.

According to the California Department of Health Services, 42.2% of reported equine WNV cases in 2004 were fatal. Gregory L. Ferraro, DVM, director of the Center for Equine Health at the University of California, Davis, School of Veterinary Medicine, says the equine mortality rate is probably exacerbated by several factors.

"There's an economic barrier in effect here," said Ferraro. "Many people simply can't afford to call out a veterinarian, have their horses vaccinated, and then have the veterinarian come out again to give the second shot. As a result, when those horses become infected with West Nile, the owners generally elect to have the animals put down rather than have them treated because they can 't afford to treat them."

The WNV vaccination calls for an initial series of two shots, followed by annual or bi-annual boosters. Depending on where you live in California, one vaccine injection when combined with farm call charges could cost as much as $100, according to Ferraro.

Another disturbing factor recently reported by the California Department of Health Services is that many equine cases of WNV might have not been reported to state officials. "In some cases, owners of horses exhibiting signs WNV instructed their veterinarians to euthanize the horses immediately rather than spend money on confirmative testing or treatment," said Ferraro.

"Consequently, there is a possibility we have many more cases of death by West Nile than currently documented. State health authorities feel it is very important to compile the complete list of fatal equine WNV cases and are working to track down any unreported cases as soon as possible," he added.

Ferraro said California is doing a great job bridging the language barrier as well, helping non-English-speaking horse owners and caretakers identify WNV. The state 's WNV web site ( features announcements in English and Spanish. Printed materials are provided in a number of languages, including English, Portuguese, Spanish, Chinese, and Russian. Pictures and videos are available to show horse owners what WNV infection looks like, why they should vaccinate their horses, and how they can go about doing it.

However, Ferraro thinks addressing the cost of WNV vaccinations should be California 's focus right now. "A lot of the veterinary associations and riding clubs in California have organized vaccination clinics to be able to vaccinate horses for people who couldn't afford the usual ranch call and vaccination fee," he said. "I know for us, if we want to cut down the deaths and increase the vaccinations, this is something we 're going to have to address."

About the Author

John V. Wood

John V. Wood is an Emmy Award-winning journalist, and now teaches his craft to high school students in North Carolina. Wood has been published in numerous national magazines/newspapersover his career, and published his first book in June 2010. Wood currently lives in Willow Spring, NC.

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