California is bracing for West Nile virus (WNV). N. James MacLachlan, BVSc, PhD, Professor and Chair of the Department of Pathology, Microbiology, and Immunology at the University of California, Davis, said that he and his colleagues expect to see the first dead birds infected with WNV in April, followed by the first horse and human cases in June and July. To help California horse owners prepare, the UC Davis Center for Equine Health (CEH) conducted a WNV seminar on March 9.

At the seminar, which was sponsored by the three major Southern California racetracks and horsemen’s groups, UC Davis veterinarians distributed a recommended vaccination schedule for California horses. Gregory L. Ferraro, DVM, director of the CEH and moderator of the seminar, said, “California will undoubtedly become affected this summer, so horsemen need to heed the lessons learned by the experience of other states and properly prepare themselves now.”

Last year, one isolated, unexplained case of a woman infected with WNV occurred in California. There also was one equine case, but that horse had come from Nebraska, where it apparently had contracted the disease.

John Madigan, DVM, MS, Dipl. ACVIM, professor and associate director of the large animal clinic at UC Davis, said that UC Davis recommends, “When the first West Nile cases are confirmed in California, booster all horses that haven’t been vaccinated (in the last) six to eight weeks.” Madigan added that he and his colleagues are recommending boosters every six months