West Nile virus spikes among horses
Oct 6, 2025, 8:00 AM
FILE: Paige Clem, Utah Cowgirl Collective, works with her horse in Ogden on Thursday, June 20, 2024. (Jeffrey D. Allred, Deseret News)
(Jeffrey D. Allred, Deseret News)
SALT LAKE CITY — The Utah Department of Agriculture and Food wants all horse owners to vaccinate their animals against West Nile virus. This comes in response to an increased number of cases across the state.
The UDAF confirms that horses in the following counties have tested positive for West Nile virus:
- Utah: 5 cases
- Box Elder: 3 cases
- Cache: 3 cases
- Weber: 2 cases
- Davis: 1 case
- Uintah: 1 case
- Salt Lake: 1 case
- Rich: 1 case
- San Juan: 1 case
- Tooele: 1 case
- Summit: 1 case
So far, six horses have had to be euthanized because of the disease.
Related: West Nile virus detected in 11 mosquito pools
“This year we seem to have a lot more cases of equine West Nile than we’ve had in the previous few years,” said Karl Hoopes, Veterinarian and Utah State University Extension Equine Specialist. “Last year, I don’t think I treated any horses with West Nile. This year I treated three.”
The West Nile vaccine is the most effective way to protect horses from West Nile virus, according to State Veterinarian Dr. Amanda Price. And while it’s better late than never, Hoopes believes this is something that should really be happening in the spring.
“It’s going to take them several weeks before the immune system is built up, the immune response that you want. So you have to plan and do it in plenty of time before those mosquitoes show up,” Hoopes said.
West Nile virus is spread by mosquitoes. They often carry the disease after biting infected birds, then spread it by moving to another animal. In horses, West Nile virus manifests itself neurologically.
“That’s going to cause them to stumble, to fall; their balance is off. And they can be dangerous if they’re stumbling around, and they fall on you, they can really hurt you,” Hoopes said.
Horses need to be able to stand for all of their bodily systems to function properly. If a horse is unable to stand for over 24 hours, it can be deadly.
For more information about West Nile virus vaccination for horses and disease prevention, visit https://ag.utah.gov/documents/Equine-West–Nile-Encephalitis.pdf or contact your local veterinarian.
