Monday, August 13, 2018

Slow start for West Nile virus

Chris McGann

A Grant County Quarter Horse named Tiny tested positive for West Nile virus last week. According to WSDA Veterinarian Dr. Brian Joseph, the five-year-old gelding is the first horse in Washington identified with the disease this year.
Horses' best protection against West Nile virus is vaccination. 

Although West Nile virus can be fatal, Tiny is receiving care for a neurological deficit in the right rear and his prognosis appears to be good.

Last year, nine horses were diagnosed with West Nile virus statewide, and just two years earlier, 36 cases were reported in Washington, with several horses dying or being euthanized as a result of the disease.

Joseph said the positive test comes as no surprise.

“It happens every year,” he said. “But this is a good reminder. It’s so easy to prevent if you vaccinate.”

Horse vaccination for West Nile virus  requires two doses and annual boosters. It is most effective when given to horses in spring, before mosquito season.

“But it’s never too late to vaccinate,” Joseph said. “It’s so easy to prevent it.”

Records indicate Tiny may have received one of the West Nile virus vaccinations which may have helped reduce the danger.

“There’s about a 30 percent mortality for horses showing severe neurological symptoms,” Joseph said. “Most horses show milder, flu-like symptoms or no symptoms at all.”

West Nile virus is spread by mosquitoes that have fed on infected birds and while it can sicken people, horses, birds and other animals, it does not directly spread from horses to people or other animals.

“People and horses are “dead end” hosts,” said Joseph, explaining that the disease does not travel directly from horse to horse – or person to person.

Other preventative measures include mosquito control, which reduces the horses’ contact the main vector or the disease. Circulating air around stalls can really help.
West Nile virus is not spread between horses. Mosquitoes are
the main vector, passing the virus from birds, such as crows. 

This first West Nile virus case showed up a little later in the year than normal, the dry hot weather may have contributed by reducing the habitat for mosquito larva, Joseph said.

Watch for symptoms

West Nile virus is prevalent across the country, so it’s always a good idea to keep an eye out for signs of infection in horses. Closely observe your horse and look for signs, which include:

• Fever of 102.5 degrees F or higher
• Discharge from eyes or nose
• Limb edema or swelling
• Spontaneous abortions
• Neurologic signs such as an unsteady gait, weakness, urine dribbling, lack of tail tone and recumbency.

Veterinarians who diagnose potential West Nile virus cases should contact the State Veterinarian’s Office at (360) 902-1878.

Visit WSDA’s West Nile virus webpage or the state Department of Health for more information.