Released April 21, 2008

BROOKINGS, S.D. - There’s still a need to vaccinate horses against West Nile Virus, a South Dakota State University specialist said.

SDSU Extension Veterinarian Russ Daly said that although numbers of cases of West Nile Virus in horses is down significantly in recent years, that’s due mainly to the success of the vaccine. The mosquito-transmitted disease is still a threat in South Dakota, and non-vaccinated horses are still at risk. Last year, eight horses with laboratory-confirmed West Nile virus infection were reported to the South Dakota Animal Industry Board. None of the horse had up-to-date vaccinations against the virus.

“Vaccinating horses for West Nile is a safe and effective management procedure,” Daly said. “Field observations suggest that vaccinations prevent the vast majority of clinical cases of West Nile Virus infection in horses, and that horses that have been vaccinated are much less likely to die if they do become infected with West Nile Virus.”

Daly said epidemiological data suggests that vaccinated horses are three to 16 times less likely to die from West Nile Virus infections than are non-vaccinated horses. Few adverse reactions have been reported from the vaccine.

West Nile Virus vaccine requires annual boosters. It is recommended that horses receive their boosters in May, to coincide with the onset of mosquito season.

If horses have not previously been vaccinated, a two-dose schedule is recommended. Different vaccine products will vary slightly in the interval between vaccinations, so label directions should be closely followed. Foals experiencing their first mosquito season in South Dakota should get a series of two or three vaccine doses, generally beginning when they are three to four months of age.

SDSU Extension Extra 11009, “What you need to know before vaccinating your horses for West Nile Virus,” has more information. Find it online at this link: http://agbiopubs.sdstate.edu/articles/ExEx11009.pdf. Or ask at your county Extension office.

As with any animal health issue, horse owners need to consult with their veterinarians for specific recommendations for their animals, Daly said.

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http://agbionews.sdstate.edu/story.cfm?id=4309

Contact: Lance Nixon, (605) 688-4653, Lance.Nixon@sdstate.edu