BATON ROUGE, La — Mosquito activity soon will be increasing, and an LSU AgCenter veterinarian says now is the time to vaccinate horses to protect against various strains of encephalitis.

LSU AgCenter veterinarian Steve Nicholson says Louisiana horse-owners need to protect their animals each year against Eastern Equine Encephalitis, Western Equine Encephalitis and West Nile Virus.

The diseases are transmitted to horses by mosquitoes infected with them, and acute cases of some of them can be fatal for the animals.

"Last year West Nile Virus was very active in birds and affected hundreds of horses in Louisiana," Nicholson said recently. "Many people are questioning whether it will appear again and cause an outbreak in horses this year."

The veterinarian says a major outbreak may not occur this summer because horses could have some degree of immunity from natural exposure or from being vaccinated last year. But he still stresses all horses should be vaccinated this year anyway.

"Basic vaccination of adult horses should include annual or semi-annual booster shots for Eastern, Western and West Nile Virus encephalitis," Nicholson said, adding, "The West Nile Virus vaccine appears to be an effective product — although it still is conditionally approved and efficacy studies are ongoing."

Nicholson also says foals and colts of immunized mares should receive initial series of the vaccine at three months to six months of age. Foals of unvaccinated mares can be vaccinated at one month and receive the booster monthly through six months of age.

For more information, horse owners are urged to discuss encephalitis vaccinations and other disease vaccinations with their veterinarian.

In addition, information on Eastern Equine Encephalitis is available in the free LSU AgCenter publication, "Questions Regarding Eastern Equine Encephalitis and Horses," which can be obtained through parish LSU AgCenter Extension offices or on the Web at: www.lsuagcenter.com/Communications/pdfs_bak/pub2834equine.pdf.