The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) reported the first equine West Nile virus (WNV) case of the year in the Toronto area.


The horse displayed signs of fever, muscle tremors, gait abnormalities (ataxia) and weakness. The horse’s vaccination history is unknown; the horse is recovering under veterinary medical supervision.

In 2015, OMAFRA reported three WNV cases in horses.

West Nile virus is spread by mosquitoes that have fed on infected birds. The disease sickens people, horses, birds and other animals, but it does not spread directly from horses to people or other animals.

The disease is fatal to horses in about a third of the cases in which clinical signs are apparent, although most horses do not become ill and show no symptoms. Horses that do become ill can appear to be displaying loss of coordination, loss of appetite, confusion, fever, stiffness, and muscle weakness, particularly in their hindquarters.

Spring is the best time to vaccinate horses against West Nile virus or obtain an annual booster shot. However, horses may still benefit from first-time vaccinations or an annual booster shot.