In recent weeks, two horses in the Cache Creek area have shown clinical signs of West Nile virus infection, says Langley veterinarian John Twidale.
In a press release, he said “Blood tests on both horses show high levels of antibody against the virus, indicating active infection.”
For many years, vets and horse owners have been expecting to see the virus in B.C., as it has been active in all the western provinces and U.S. states.
“It appears this will be our year,” Twidale said.
Clinical signs include muscle tremors of the face, chest and body, weakness in the hind legs, fever, depression and in severe cases inability to stand, caused by the virus attacking the brain and spinal cord nerves, similar to polio in humans. Treatment of affected horses can only be supportive, as antibiotics are not effective against virus infection.
Vaccination prior to exposure is the only way to prevent infection, and it is too late to vaccinate after symptoms appear.
Most horse owners are well aware of the dangerous consequences of West Nile infection and vaccinate annually, but many have decided to take a chance and miss annual booster shots. Veterinarians strongly recommend that all horses receive an annual booster vaccine to ensure a high level of immunity.
Even if the horse has missed a year or two, a booster shot will restore immunity in a few days. If a horse has never been vaccinated for West Nile, he should receive two doses, two to four weeks apart, then one annually.
In addition to vaccination, horse owners should take precautions to reduce the mosquito populations around the barn and pasture areas, avoid having horses out when mosquitoes are active, and use fly sheets and face masks when horses are turned out.
“West Nile is a serious disease where prevention is better than cure, as there is no certainty that the horse will survive the acute infection, or may be left with long term muscle weakness and unsound for use,” he said.
Twidale is the chair of the equine committee, of the Society of B C Veterinarians.