The Daily Inter Lake

A horse infected with West Nile virus was euthanized in Flathead County, becoming the sixth confirmed equine case in Montana and the first Flathead case this year.

State Veterinarian Dr. Tom Linfield said the horse was purchased about two weeks ago from Pondera County and was likely infected prior to coming to the Flathead.

Pondera borders Flathead County.

Local veterinarians Hugh Rogers and Pam Barker of Alpine Animal Hospital initially saw the horse on Sept. 2. The horse had not received a West Nile virus vaccination.

So far this year, horses have been diagnosed with the virus in Yellowstone, Blaine, Hill, Cascade, Lewis and Clark, and now Flathead County. All but the Yellowstone County horse either died or were euthanized.

None of those horses was vaccinated except a Lewis and Clark animal and its vaccination was not current.

Also this year, a golden eagle from the Raptor Center in Bozeman in Gallatin County was confirmed to have died of the virus.

A mosquito-borne virus, West Nile has infected five humans this year in Carbon, Liberty and Custer counties. In 2003, 228 people became infected with 4 deaths were attributed to the disease.

West Nile took the lives of 70 of the 193 horses diagnosed in 2003.

A viral disease that affects the nervous system, West Nile is not spread from horse to horse, horse to person, or person to person. Only the bite of the mosquito transmits the disease.

About 80 percent of people infected notice no symptoms while about 20 percent get mild flu-like symptoms. About one in 150 people develop a severe illness while one in 1,000 diagnosed die of the disease.

The virus poses the greatest risk to people over 50 or those with compromised immune systems.

To avoid infection, health officials advise people to use repellents with DEET, wear long-sleeved shirts and pants, and rid their properties of standing water sources.

"Equine vaccines for the protection of health horses against disease from West Nile virus are available through veterinarians," Linfield said.

Horses require two doses administered three to six weeks apart, followed by an annual booster vaccination. Veterinarians also have an antibody medicine available to aid in the treatment of infected horses.

Linfield advises horse owners to thoroughly clean livestock watering troughs as well as removing other sources of standing water like old tires.

"Insect repellents can also be used, and if possible, keep horses in stalls at night," Linfield said.

Signs of the infection in horses include loss of appetite, depression, weakness or paralysis of hind limbs, muzzle twitching, impaired vision, head pressing, aimless wandering, inability to swallow, hyper-excitability, convulsions or coma.

Reporter Candace Chase may be reached at 758-4436 or by e-mail at cchase@dailyinterlake.com