Horses are at highest risk of contracting West Nile virus (WNV) during peak mosquito activity, which occurs July through October in the United States. However, there’s still an opportunity to help protect horses against this life-threatening disease: Veterinarians and owners can still vaccinated horses against WNV.

“West Nile continues to be a major concern for the equine community, so it’s critical that horse owners and veterinarians remember to vaccinate horses annually against this deadly disease,” said Kevin Hankins, DVM, MBA, senior veterinarian for Zoetis Equine Technical Services. “A horse that is not vaccinated annually is still very much at risk, which is why we continue to see a great number of West Nile cases in unvaccinated horses.”

West Nile virus is transmitted by mosquitoes—which feed on infected birds—to horses, humans and other mammals. Vaccination remains the most effective way to help protect horses against West Nile and other mosquito-borne diseases. If vaccinated, horses have shown to be 30 times less likely to contract West Nile.

Horses that have been vaccinated in past years will need a booster shot annually or every six months, depending on where the animal resides. However, if horses went unvaccinated in previous years, the horse will need a two-shot vaccination series within a three- to six-week period