Spring returns West Nile threat

While spring turns a young man's fancy to thoughts of love, the threat of West Nile virus begins to keep health officials awake at night.

The potentially deadly virus surfaced last year after a fast and furious run toward Western Montana the year before. Against all predictions, only six people in Montana tested positive for West Nile virus in 2004. In 2003, four people died of the virus in the state while 228 tested positive.

The virus exerted the most deadly impact on Montana horses.

In 2002, 38 horses died or were euthanized. In 2003, 70 out of 193 horses diagnosed either died or were euthanized as a result of West Nile virus.

Unlike humans, horses have a weapon against the disease. Flathead County Health Officer Joe Russell urged horse owners to protect their animals with one of several USDA approved vaccines.

"It's not too early for the equine side to get mobile," he said.

Russell urged horse owners to "get ahead of the curve."While horses may still acquire the West Nile virus, the vaccination improves the animal's survival.

When the virus hit hard in 2003, less than 10 percent of horses that tested positive were vaccinated. In 2004, only one of 11 horses testing positive was vaccinated and that horse survived.

Montana State Veterinarian Tom Linfield said horses not previously vaccinated need two doses given three to six weeks apart. Vaccine manufacturers recommend an annual booster after the initial two doses.

According to Linfield, some veterinarians recommend two boosters each year, particularly for horses in high-risk areas for virus infection.

Approved vaccines include combination products which protect against West Nile virus, eastern, western or Venezuelan equine encephalitis and tetanus.

The veterinarian listed signs of encephalitis in horses as loss of appetite and depression.

These symptoms appear with any combination of weakness or paralysis of hind limbs, muzzle twitching, impaired vision, lack of coordination, head pressing, aimless wandering, convulsions, inability to swallow, circling, hyper-excitability or coma.

"These are also clinical signs of western and eastern equine encephalitis, viral diseases that affect the central nervous system and can cause severe complications and death in horses," Linfield said.

He said these diseases with similar symptoms, including rabies, also affect humans. Linfield said vaccination and mosquito control continue as the most effective prevention for horses.

Mosquito control provides the only weapon public health officials have to protect vulnerable humans, including elderly and young children, from West Nile virus.

Russell said no one knows how hard the mosquito-borne virus may hit this spring. But he said the county has to prepare as much as resources allow.

In the next few weeks, the county's mosquito control contractor begins surveillance for floating larvae logs for treatment with chemical larvicide.

"We have some budget for that," Russell said.

A bill before the Montana State Legislature could make it easier for counties to pay for expanded prevention in crisis mosquito years. Russell said that HB 218, authored by Rep. Bernie Olson, streamlines the process of setting up a mosquito control district.

If the legislation becomes law, county commissions could create a district by adopting a resolution of intent. The bill also reduces the number of signatures needed on a petition if property owners elect to set up district.

"It's still a public process," Russell said.

Before adopting a resolution, commissioners must hold a public hearing. Property owners must notify all non-resident property owners within the proposed tax district for mosquito control.

Montana law limits the tax to two mills.

Because of the public health threat from mosquitoes, Russell said he supports the legislation that makes forming this tax district easier.

"I wouldn't want to see other taxing districts created this way," he said. "It's a taxing authority, not a service district, although some may not agree with me."

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