Lisa Kronstedt grasped the green halter with one hand and the filly's tail with the other, calming the thoroughbred while a veterinarian injected the West Nile vaccine Wednesday.

Kronstedt and Bob Dainty, owners of the Shamrock Valley Farm near Stillwater, had already vaccinated their thoroughbred mares last spring, including four that they race as champions at Canterbury Downs.

"There is peace of mind in vaccinating," Dainty said.

He and Kronstedt had trusted the advice of their veterinarian, Dr. Donna Rued of River Valley Veterinary Services. Wednesday, she visited the farm to vaccinate their foals.

As she and the couple stood in a pasture, Rued spoke of the potentially deadly virus that has been confirmed in two birds in Minnesota. The virus is carried by birds and spread by mosquitoes to humans and horses. Horses are more susceptible than people.

Dainty and Kronstedt are among many horse owners in Minnesota who have vaccinated their animals. The virus has fanned across the nation, killing 18 people and an estimated 200 horses since it was detected in New York City in 1999.

Tests are being conducted on two horses, one in Hennepin County, the other in Clay County. Minnesota has an estimated 57,000 horses.

Rued said she worries most about horses in family settings that haven't been vaccinated.

"All of the big barns are aware of it and are protected," she said. "The small back-yard horse owners are more susceptible because they don't have barns. Those horses sleep outside, where all of the mosquitoes can get at them."

Dr. Terry Arnesen, owner of the Stillwater Veterinary Clinic, said the disease has spread more quickly than anticipated. He, like Rued and many other veterinarians, stocked up on the vaccine last winter. Arnesen said there was a shortage caused by back orders last year as much of the vaccine, made in Fort Dodge, Iowa, went to counter an outbreak in Florida.

Vets have been busy

It remains to be seen whether the news in Minnesota will cause back orders to mount. The company that makes the vaccine did not return calls Wednesday.

So far this year, Anoka Equine Veterinary Service, the largest horse clinic in the state, has vaccinated 85 to 90 percent of the 5,000 or so horses it services, said Dr. Kim Voller.

"We have been urging our clients to vaccinate against it, but we haven't had to urge them much," Voller said. "They've heard it's moving this way."

The virus has been diagnosed in 720 horses nationwide since 1999, officials say.

"An ounce of prevention is worth a pound of cure," said Dan Ramberg, owner of Woodloch Stable in Hugo and Bunker Park Stable in Coon Rapids. "Anytime you have a virus or disease spread by mosquitoes, you're vulnerable."

He vaccinated his nearly 200 riding horses last spring. Vaccinations typically cost $10 to $18 each, plus the veterinarian's charge.

That's a small price to pay to protect your horses, said Kronstedt, who with Dainty breeds and raises racehorses worth tens of thousands of dollars. To lose one to disease would be devastating, they said.

"It's not just the money; it's the time and who they are to us," Kronstedt said.

Of the four high-stakes thoroughbreds they race at Canterbury, two were the first horses that she and Dainty bred and raised after they bought their 20-acre spread in Grant Township in 1993.

Love for horses

Now, when they sit at the track and watch, it's an adrenaline rush to see their horses cross the finish line, Dainty said. Kronstedt said their emotions range from thrill to heartbreak.

"You get the highest highs and the lowest lows in horse racing," she said. "One day you win and the next day you don't even place."

Even after the lows, she said, the couple come home to their beloved horses, which they tend full time. They pamper their horses with so much attention that the horses nuzzle up to visitors, seeking strokes on their glossy chestnut and bay coats.

Rued told the couple that many of the practices they've been doing all along, such as mowing long grass and removing standing water, will now help protect their horses from the West Nile virus.

On Wednesday, as she does daily, Kronstedt hosed down the couple's dozen horses, the mosquito-attracting sweat washing off like suds. Then she sprays them with insect repellent and turns buckets upside down.

The pond and creek on their farm and the lake just behind it provide water that helps mosquitoes breed. And each day, the couple see 20 to 30 crows and many more birds flying around the farm. Now those birds could be potential carriers of the West Nile virus.

"You just take the preventative measures," Dainty said. "Vaccinate and pay attention to your surroundings the best you can and hope you don't contract anything."

-- Joy Powell is at jpowell@startribune.com.