Partridge ? Veterinarians are encouraging Kansas horse owners to vaccinate their animals against the West Nile Virus this month before mosquitoes begin flying.

West Nile, a mosquito-borne virus, first appeared in the United States in 1999 and hit Kansas last August. Transmitted through the bite of an infected mosquito, the virus multiplies and can cause illness once in the horse’s bloodstream.

After last year’s outbreak and with mosquito season just around the corner, horse owners are beginning to take precautionary measures.

“We could start vaccinating any time now,” Hutchinson veterinarian Dr. Roy Russell said.

Russell and other area veterinarians were busy last summer and fall administering vaccinations to horses. In Reno County, only 15 horses were diagnosed with West Nile. The Kansas Department of Health and Environment reported 800 cases in horses and mules through blood samples tested at Kansas State University.

Partridge farmer Doug Harner and his family know firsthand what it’s like to be told a horse has West Nile.

“It’s hard to explain how we felt,” Harner said. “We were really floored by it.”

The Harners’ horse recovered. But this year they are taking precautions with a vaccine.

Birds can transmit the virus to mosquitoes, Harner said, which then can transmit it to horses and humans. Mosquitoes are the only known transmitter of the virus. Only a few cases have been reported in other domestic animals.

Symptoms in horses include hyperactivity followed by depression, failure to respond, lack of coordination, staggering and convulsions. Kansas State University statistics show West Nile has about a 30 percent mortality rate in horses.

Russell said the vaccine requires two doses, three weeks apart. Horses vaccinated last year should get a booster. The cost per dose is about $20.

“It is an expensive virus and difficult, also, because the nervous system is involved,” Russell said, noting figures from Kansas State show that the average owner’s cost for animals that were referred to the university for treatment and survived was about $2,000.

Horses shouldn’t be vaccinated too early, though, so the dose won’t wear off before the season is over. Russell recommended another booster after four months to ensure immunity.