West Nile Virus in Horses: Symptoms, Diagnosis, and Treatment

West Nile Virus (WNV) is a mosquito-borne flavivirus affecting horses and humans. In horses:

Clinical Signs

• Fever, anorexia, lethargy
• Muscle fasciculations (twitching), weakness, ataxia
• Head pressing, circling, aimless wandering
• Seizures, paralysis, recumbency

Systemic Involvement

• Respiratory distress, GI ileus, renal/hepatic dysfunction
• Encephalitis (brain inflammation) common

Diagnosis

Serum IgM capture ELISA (recent exposure); PCR on CSF/blood.

Treatment

Supportive care: IV fluids, anti-inflammatories (flunixin, DMSO), anticonvulsants, sling support for recumbent horses. No specific antiviral. Mortality ~30–40% in clinical cases.

Prevention

Annual vaccination (core vaccine in endemic areas); mosquito control.