Though the Centers for Disease Control reported last week that more than 40 people have died across the country this year from West Nile virus (WNV), many horse owners can breath a little easier — the equine vaccines available are effective, according to veterinarians.
"The vaccine is safe and appears 100 percent effective by all measures," said Dr. Gary E. Hanes, serving clients mostly on the Peninsula, including Half Moon Bay and Pacifica.
The reasons to vaccinate are simple, according to Hanes. The annual cost for vaccination is low, and although the incidence of WNV in San Mateo and Santa Clara counties has been low, the case mortality rate remains at 30 to 40 percent.
"So it is a very devastating disease," said Hanes.
Sue Macinnes, owner of the longtime Coastside business, All Animal Mobile Veterinary Clinic in Half Moon Bay, also recommends vaccinating horses for WNV.
"They are very effective, though they may need to vaccinate more frequently then once a year in an outbreak," she said.
All of the clients for Southern California veterinarian Dr. Larry Kelly have been vaccinated, "for years now," Kelly told Patch. "(Horse owners) are crazy if they don't."
According to the American Association of Equine Practitioners, about one-third of horses who exhibit clinical signs of WNV infection, which is transmitted by mosquitos, will die or be euthanized. Of the horses who survive, about 40 percent will still exhibit residual effects — such as gait and behavioral abnormalities — six months after they were diagnosed.
"(WNV) is a neurologic problem, and it's most difficult … to turn a horse around from the disease," Kelly said.
Symptoms of WNV in horses include fever, weakness, wobbles, seizures, falling down or even behavioral or mood changes, Kelly said.
The vaccines, which have been around for about a decade, require a two-shot series when first administered, then an an annual booster shot, according to veterinarian Dr. Ruth Sobeck.
Because it takes about six weeks for a horse to develop full immunity after being vaccinated, Kelly recommends horse owners vaccinate early.
"It doesn't do the horse any service (for the owner) to read in the newspaper that West Nile is here and then get (their horse) vaccinated," said Kelly. Horse owners should "think well ahead of what they want to do (and) … have these horses super-vaccinated by the time the disease is rolling through."
In California this year, 11 horses were positively diagnosed as infected with WNV, according to the California Department of Food and Agriculture. Three of the horses — including an unvaccinated yearling colt — were euthanized.
None of the 11 horses were located in San Mateo County, according to the CDPH. The total number of West Nile cases found in San Mateo County is 15, and includes mostly squirrels and birds. The disease was first discovered in horses in the state in 2003.
"Virtually every equine death in California from WNV has been in unvaccinated or incompletely vaccinated horses (never received initial booster dose or were done by an owner using poor vaccination technique)," said Hanes. "To vaccinate is a no-brainer."