“West Nile virus (WNV) is coming to a state near you if it hasn’t already arrived,” said Eileen Ostlund, DVM, PhD, head of the equine/ovine viruses section at the Diagnostic Virology Laboratory, National Veterinary Services Laboratories in Ames, Iowa, during the Western Veterinary Conference held Feb. 15-19 in Las Vegas, Nev. In a comprehensive overview of WNV’s activity in the United States since its arrival in 1999, she discussed its transmission methods, hosts, U.S. history, clinical signs, diagnosis, vaccination options, impact on the U.S. horse
population, duration of immunity, and supportive care.

In four years, the disease has spread all the way across the country and infected thousands of horses. “Now it’s pretty much coast to coast and obviously not going away,” she said. “The greatest number of cases tend to occur in September and October.”

Birds and Mosquitoes

Ostlund noted that WNV has been found in more than 130 bird species to date. “It’s not a picky virus in terms of its hosts,” she said. “No state lacks birds that can harbor WNV