Vaccinate for West Nile Virus Now

Frederick Harper, Extension Horse Specialist
Department of Animal Science
Horse owners are urged to vaccinate/booster their horses against West Nile Virus (WNV) before the mosquito season. Horses never vaccinated require two injections several
weeks apart. The horse does not have immunity for three to four weeks after the second injection. Horses vaccinated last year need an annual booster before the mosquito season.
There are now two vaccines available that protect against WNV. Your veterinarian can provide information on these two products.

The number of positive WNV horses dropped from 150 in 2002 to 103 in 2003, a decrease of 30 percent. The death rate declined from 28 percent to 16.5 percent.
In 2003, eastern Tennessee had a high number of positive WNV horse cases; whereas, western Tennessee was the hot area in 2002. A low incidence of WNV in an area last year is no indication there will be fewer affected horses this year. It is recommended that all owners have their horses, mules and donkeys vaccinated for WNV soon. For additional and current WNV information, check our WNV Web site: http://animalscience.ag.utk.edu/.