Oregon Pony Euthanized Due to WNV
The affected filly was unvaccinated against West Nile virus, which is spread by mosquitoes.
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The affected filly was unvaccinated against West Nile virus, which is spread by mosquitoes. | Photo: iStock
On Sept. 28, Oregon officials confirmed that a yearling Welsh pony filly at a private facility in Jackson County was euthanized after contracting West Nile virus (WNV). The filly began showing signs, which included colic and neurologic deficits, on Sept. 17. She was unvaccinated against WNV.
About West Nile Virus
WNV transmission occurs when infected mosquitoes feed on animals, as well as humans, after having fed on infected birds.

Clinical signs of WNV in horses include:
- Mild anorexia and depression
- Fine and coarse muscle and skin fasciculation;
- Hyperesthesia (hypersensitivity to touch and sound);
- Changes in mentation (mentality), when horses look like they’re daydreaming or “just not with it”;
- Occasional drowsiness;
- Propulsive walking (driving or pushing forward, often without control);
- Spinal signs, including asymmetrical weakness; and
- Asymmetrical or symmetrical ataxia.
West Nile virus has no cure; however, some horses can recover with supportive care. Equine mortality rates can reach 30-40%. The American Association of Equine Practitioners includes WNV as one of the core diseases all horses should be vaccinated against at least annually.
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