06/02/2026
West Nile Virus in Horses: Preventing the Preventable
As mosquito season ramps up across Saskatchewan, it's an important time to think about West Nile Virus (WNV) protection for your horses.
West Nile Virus is a mosquito-borne disease that can have devastating consequences. When an infected mosquito bites a susceptible horse, the virus can enter the bloodstream and eventually cross the blood-brain barrier, causing damage to the brain and spinal cord. While not every infected horse will become ill, those that do often develop serious neurologic disease.
Infected horses that develop illness typically show neurologic signs such as ataxia (limb incoordination, especially of the hind limbs); face, neck, or trunk muscle twitching; and fever. Many horses also exhibit behavioural changes such as hyperreactivity or depression. In severe cases, horses might progress to recumbency (inability to rise), paralysis, coma, and death.
Widespread vaccination efforts resulted in a dramatic drop in infection rates across the country. Both the killed and recombinant forms of the WNV vaccine promote excellent immunity when administered according to recommendations. For both vaccine types, veterinarians recommend administering an initial two-dose series, four to six weeks apart. The second booster vaccine is crucial for protective immunization; especially for younger horses. Horses that only receive the first vaccine are not considered fully protected.
