Safeguard For Spring: West Nile Virus

As spring approaches, the topic of West Nile Virus comes up more and more. In 2016 there were 10 confirmed positive cases of WNV in Alberta, in 2017 there were 11 and last year, in 2018, there was a huge spike in Alberta, with over 73 cases confirmed.
Credit: Alberta Government

About West Nile:

West Nile Virus (WNV) is a viral disease that is transmitted by mosquitoes who acquire the virus from infected birds. WNV is a mosquito-borne virus that can cause inflammation or swelling of the brain and spinal cord in horses, birds and humans. Only certain species of mosquitoes spread WNV, these mosquitoes become infected as they feed on infected wild birds such as crows, blue jays, magpies and ravens. The prevalence of WNV varies from year to year and the occurrence of the disease tends to peak in summer and early fall when standing water and other mosquito larva habitats are present, and following extended periods of warm weather.

In horses, West Nile Virus causes an encephalomyelitis, or brain and spinal chord infection. Most horses bitten by a mosquito infected with WNV will not develop clinical disease. Affected horses, which show no progression of gait abnormalities, usually recover completely with no consequences within 5-15 days.

Signs & Symptoms:

Signs and symptoms that your horse is infected with West Nile generally appear within 5-22 days after initial infection. They could include lack of interest in surroundings, weakness of limbs, inability to swallow, ataxia (degeneration of the nervous system), abnormal muscle twitching and loss of appetite. Horses may also loose coordination, including stumbling and losing the ability to stand back up after laying down. They can succumb to fever, and unfortunately, in severe cases, death.

The signs discussed above may be confused with other nervous system disorders in horses such as rabies, sleeping sickness, equine herpes virus and tetanus.

Over one third of horses showing clinical disease may die or have to be euthanized because of complications. Unfortunately, sometimes horses that do recover may still exhibit permanent neurological symptoms.


Since mosquitoes are associated with WNV transmission, insect control is important. The species of mosquito responsible for West Nile Virus infection breeds in small, warm, still puddles of water. These are generally found in poorly drained eaves troughs, bird baths, discarded rubber tires and even hoof prints formed in mud. Preventative measures include the removal of stagnant water and tall vegetation, as well as the use of insect sprays and repellents. Horse owners also need to watch for dead birds and properly dispose of them on their properties.


One of our main preventative recommendations is to vaccinate your horses as a safe guard against West Nile Virus. At Energy Equine we regularly reach for and recommend Vetera Gold. Not only does it offer 12 month WNV duration of immunity, it also protects against Influenza (Clade 1 and Clade 2), Herpes (EHV-1 and EHV-4), Eastern and Western Encephalomyelitis and Tetanus. Vetera Gold’s dual phase system delivers both rapid and long-lasting immunity and is a safe, high-quality vaccine.


In Alberta we have seen an alarming rise in WNV over the course of just one year. It’s important to also note that equine athletes that are regularly showing and travelling are in a high risk demographic. Each horse owner’s vaccination protocols should be discussed with their veterinarian, and determined to fit the needs of their horse. If you have any questions about vaccinations this spring, and what is right for your program, please contact Energy Equine at (403) 700-0818, or email us at