“West Nile virus (WNV) is the number one diagnosed neurologic disease in horses, or close to it,” said William Saville, DVM, PhD, Dipl. ACVIM, of The Ohio State University, at a March 10 Fort Dodge Animal Health educational seminar for veterinarians held in Lexington, Ky. “Because of the decreased number of cases in 2003 compared to 2002, people are starting to think we’ve got WNV under control, but we haven’t,” he said. “We need to convince horse owners that prevention is the only way to go.”

The veterinary and horse-owning communities have watched WNV radiate across the United States since 1999, spreading via infected mosquitoes and birds. Forty-four of the lower 48 states had confirmed WNV cases in some species in 2003. “Why has WNV moved from East to Westa so fast?” Saville asked. He said that crows (which are highly susceptible to the virus) can move up to 200 miles in east-to-west migratory patterns, and other migratory birds and container traffic such as trucks and planes might have aided the western movement of birds and mosquitoes.

Saville used 2002 to illustrate the spread and behavior of the virus. That year, the middle of the country was hit with more than 14,000 confirmed equine cases. He thinks that many people never bothered to have affected horses tested, so the number of cases was probably higher