West Nile Virus

This disease is life-threatening and should be treated by a veterinarian swiftly.

West Nile Virus is a serious threat to horses with an estimated average case fatality rate of 30–40%.
West Nile Virus (WNV) is a mosquito-borne virus that can cause encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord) in horses.

Mosquitoes acquire the virus from infected birds and transmit it.
WNV cannot be spread directly from horse to horse.
A WNV infected mosquito is required in all cases.
WNV is at its lowest levels in early spring and builds in intensity as the summer season progresses.

Symptoms

Common in

Treatment

Depending upon the effect the virus has on each horse will determine if home or clinical care is warranted. All treatments should be under the direction of a veterinarian.

Treatment includes anti-inflammatories if a fever is present, ensuring the horse receives sufficient fluids, possibly through intravenous treatment if the horse is unable to drink on its own. Oral or intravenous feeding may also be necessary for horses unwilling to eat.

For horses unable to rise slinging is recommended 2 to 3 times per day to aid in circulation and to try to prevent pressure point sores. Head and leg protection is also frequently needed. Many horses will improve within 5 to 7 days of displaying clinical signs, however, about 20-30% can exhibit severe neurological deficits for several weeks.

Some horses sometimes develop other problems because they were weakened by WNV. Joint and tendon infections, sheath infections, pneumonia, and diarrhoea can all occur as secondary events.

Prevention

Horse owners should consult their veterinarians regarding vaccination. The vaccine shots are of no value if they aren’t given prior to exposure to the disease. The vaccines require two doses, administered three to six weeks apart, and full protection doesn’t develop until four to six weeks after the second dose.

To eliminate mosquito breeding habitats: Eliminate any unnecessary standing water on your property.

Stable horses inside during active mosquito feeding times (dawn/dusk), utilize fans, barrier cloths, screens, flysheets, repellent sprays (permethrin), turn off lights that attract mosquitoes at night or use fluorescent lights, which do not attract mosquitoes.