West Nile Vaccine

WEST NILE VIRUS

Identified in United States, most of Canada and Mexico.
Transmitted from avian reservoir hosts by mosquitoes.
Horses and humans are considered to be dead-end hosts for WNV (the virus is not directly contagious from horse to horse or horse to human).
Fatality rate is ~33%, and 40% of horses that survive still exhibit residual effects, such as gait and behavioral abnormalities.
Epidemiological studies have demonstrated high efficacy for vaccination.
Vaccination for West Nile virus is recommended as a core vaccine by American Association of Equine Practitioners (AAEP).

Adult horses previously vaccinated: Vaccinate annually in the spring, prior to the onset of the insect vector season.

Adult horses previously unvaccinated or having unknown vaccinal history : A primary series of 4- to 6-week interval between doses. Re-vaccination interval is 12 months. Pregnant mare previously vaccinated: Vaccinate at 4 to 6 weeks before foaling.

Pregnant mares unvaccinated or having unknown vaccinal history : Limited studies have been performed that examine vaccinal protection against WNV disease in pregnant mares. While none of the licensed vaccines are specifically labeled for administration to pregnant mares at this time, practitioners have vaccinated pregnant mares due to the risk of natural infection. It is an accepted practice by many veterinarians to administer WNV vaccines to pregnant mares as the risk of adverse consequences of WNV infection outweighs any reported adverse effects of use of vaccine.

Foals of vaccinated mares: Administer a primary 3-dose series beginning at 4 to 6 months of age. A 4- to 6-week interval between the first and second doses is recommended. The third dose should be administered at 10 to 12 months of age prior to the onset of the next mosquito season.