Six horses in Saskatchewan, Canada, have been diagnosed with West Nile virus (WNV). Horse owners are encouraged to take preventive measures. A conditionally licensed vaccine can be obtained through your veterinarian.

West Nile virus is a flavivirus that can infect many different types of animals but causes sickness only in a small number of species. In North America, humans, horses, and especially members of the crow family (crows, ravens, magpies, blue and gray jays) are at most risk for serious illness. Illness due to WNV has not been found among sheep, pigs, and cattle. The main reservoir for the virus is thought to be wild waterfowl. The virus is spread from bird to bird, and to other animals, by the bites of mosquitoes. The horse is a dead-end host for WNV; the virus does not spread from horse to horse, or to other animals, including humans.

West Nile virus first appeared in North America in 1999 and has spread steadily across the country over the past three years. The virus was detected in birds in Manitoba in early July 2002, and has now been found in some
locations in Saskatchewan. On Sept. 4, Saskatchewan confirmed its first positive case of the virus in horses.

The vaccine for horses is not licensed for use in Canada, but it can be obtained as a conditional use vaccine. The vaccine is available through veterinarians only. The veterinarian must keep detailed records on  what horses are vaccinated (breed, age, reproductive status, etc.), lot numbers, results, and reactions. A blood sample before vaccination may be recommended especially if the horse might be exported