09/01/2026
West Nile Message from Dr. Kari Singer
Hello FVEP community, unfortunately, we have to report that we had a young horse come back positive for West Nile Virus. After reaching out to the State vet to report it, they let us know that they have been seeing a high number of positive West Nile Virus cases earlier then normal this year. If you have not yet vaccinated for West Nile Virus this year, now is the time.
Here are the symptoms to look out for:
- Clinical signs are variable and depend on the stage of disease at the time of presentation.
- Low-grade fever (101.5–103.5° F or 38.6–39.7° C) occurs in approximately 25% of affected horses.
- Fever may be preceded or accompanied by non-specific signs of lethargy and inappetence.
- Neurologic signs are often sudden in onset and may be rapidly progressive. Clinical signs reflect predilection of the virus for the gray matter of the caudal brainstem, cerebellum, and spinal cord with the cerebrum and rostral brainstem less affected. Neurologic deficits may include:
o Fine tremors/fasciculations of the muzzle, face, and neck muscles are common, and should elicit a high index of suspicion for WNV encephalopathy.
o Periods of hyperexcitability that may alternate with somnolence.
o Cranial nerve deficits including facial nerve paralysis, weakness of the tongue, and head tilt.
o Ataxia, weakness, paralysis, or dysmetria of a single limb or multiple limbs. Intermittent collapse may occur in the forelimbs or hindlimbs.
o Recumbency/inability to rise.
o Clinical signs consistent with colic
o Death
There is no treatment for West Nile Virus, there is only supportive care, so vaccination is important to try to prevent or lessen the symptoms.
