Montana animal health officials are encouraging horse owners to consult with their veterinarians about vaccinating their animals for West Nile virus (WNV) after a spike in the number of cases last year.

“We had 32 cases last year, the most since 2007, and the third highest total in the nation,” said assistant state veterinarian Tahnee Szymanski, DVM. “That’s concerning because the disease is highly preventable.”

Based on Montana Department of Livestock data, no equids that were current on vaccinations have ever contracted the disease in Montana. In contrast, one-third of unvaccinated equids that contracted the disease either died or were euthanized (161 of 492 since 2002).

Greg Johnson, MS, PhD, professor of veterinary entomology in the Montana State University Department of Animal and Range Sciences, says vaccination—which is recommended as a core vaccine by the American Association of Equine Practitioners—is prudent given WNV’s unpredictability