Protect your horses: Don’t skip the West Nile Virus vaccine
Warmer weather brings with it mosquitoes—and that means it’s time to get serious about protecting your horses from West Nile virus (WNV).
Why you should care about West Nile Virus in horses
While most cases in Washington are concentrated in Central and Eastern Washington, they can occur anywhere mosquitoes are active—from late spring through fall.
WNV is spread by mosquitoes that have fed on infected birds. It can affect people, horses, birds, and other animals, but it does not spread directly from horse to horse or from horses to humans.
The good news? Vaccination is highly effective at preventing illness in horses.
What happens if a horse gets infected?
While many horses exposed to WNV won’t show signs of illness, those that do can experience:
- Loss of coordination or balance
- Muscle weakness, especially in the hindquarters
- Confusion or changes in behavior
- Fever and stiffness
- Loss of appetite
Roughly one in three horses showing symptoms do not survive the disease.
When and how to vaccinate
Spring is the best time to vaccinate but it's never too late. The vaccine is most effective when given before peak mosquito season begins. If your horse hasn’t been vaccinated before, they’ll need two initial doses followed by annual boosters. Talk to your veterinarian now to get your horses on schedule.
Don’t forget about mosquito control
Vaccination is essential, but mosquito management matters too. Here’s how you can reduce your horse’s risk:
- Use insect repellents and fly sheets
- Eliminate standing water—clean troughs weekly and dump water out of old tires or containers
- Keep the barn area clean and dry
Reporting and resources
Veterinarians who suspect West Nile virus in a horse should report on the RAD system at https://fortress.wa.gov/agr/apps/rad/.
For more information on how to protect your animals, visit:
- WSDA: WNV webpage
- WNV FAQs
- WDOH: 2025 WNV Activity
- WDOH: Historical WNV Activity
- Washington Animal Disease Diagnostic Laboratory (WADDL)
- Equine Disease Communication Center (EDCC)