Released: April 28, 2004

Two West Nile Virus Vaccines Available for Horses This Year

MANHATTAN, Kan. – Two types of vaccine to protect horses from West Nile virus are available this year. West Nile kills about one-third of unvaccinated horses that mosquitoes infect with the virus, a Kansas State University scientist said.

Neither of the vaccines provides life-long protection. After receiving an initial two-shot series, horses still need a booster shot every spring, said Ludek Zurek, medical-veterinary entomologist for K-State Research and Extension.

Horse owners who already have protected their animals with the original vaccine should arrange for the booster shot in late April or early May. That timing will give horses enough protection during the months when the mosquito-borne virus is most likely – June through September, Zurek said.

“The vaccination obviously works,” he added. “Two years ago, 800 Kansas horses contracted West Nile virus. Last year, that number was down to 80.”

The two vaccines available now differ in that the first on the market, Innovator (made by Ft. Dodge), is based on the dead virus. The new vaccine, Recombitek (produced by Merial), is based on the live virus.

“As a general rule, live-virus vaccines kick in faster and last longer,” Zurek said. “The Merial vaccine hasn’t been field tested yet, but it’s likely to have those characteristics.”

Merial expects its shots to provide full protection two weeks after the initial vaccination series, as well as after subsequent years’ booster shot, the entomologist said. So, unvaccinated horses still could be protected from the disease this year by starting the Merial vaccination program now. The recommended start-up time for initial Ft. Dodge vaccinations is late March or early April.

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News