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2 equine cases of West Nile Virus confirmed in Montana

Posted at 5:58 PM, Aug 07, 2018
and last updated 2018-08-07 20:01:54-04

GREAT FALLS – The Montana Department of Livestock has confirmed the first reported cases of equine West Nile Virus in Montana in 2018.

The two cases are in Musselshell County and Lake County, according to a press release from the agency.

This follows detection of the virus in mosquito surveillance pools from Cascade, Hill, and Lewis & Clark counties.

There have not been any reported human cases of West Nile Virus this year in Montana.

West Nile Virus affects humans, equines, and birds. It is spread through the bites of infected mosquitos; horses cannot transmit the virus directly to people. Detection of the disease in horses and mosquitoes in Montana serve as an important reminder for people to take steps to prevent West Nile Virus infection.

“There is no direct treatment for the virus in horses, but vaccination is highly effective in preventing disease. Horses that are vaccinated rarely die or are euthanized because of the disease,” said Dr. Tahnee Szymanski, Assistant State Veterinarian.

She continued, “Vaccination is typically administered in the spring, but may offer some protection even this late in the season. Work with your veterinarian to determine if your horse could still benefit from vaccination.”

Horse owners should be aware of the typical signs of West Nile Virus which include:·

  • Fever, loss of appetite and depression
  • Incoordination or weakness of the hind limbs
  • Muscle or muzzle twitching, drooling
  • In the meantime, topical insecticides and eliminating standing water may help decrease your horse’s exposure to mosquitoes.

The mosquitoes that carry West Nile Virus are most active at dawn and dusk, so consider keeping your horses off of irrigated pastures and away from water sources during those times of day.


The Cascade City-County Health Department said on Tuesday that West Nile Virus appears to be widespread and prevalent, so residents are strongly encouraged to take steps to protect themselves.

The best defense against WNV is bite prevention. To protect yourself, use the 5 Ds:

  • DEET-Apply repellent containing an EPA-registered active ingredient, such as DEET, and follow the directions on the package.
  • DUSK and DAWN-This is when mosquitoes are most active. Try to avoid outdoor activities during these times.
  • DRAIN STANDING WATER-Standing water is the perfect breeding ground for mosquitoes. Drain such areas around your home (gutters, pools, tires, buckets, water bowls, etc.).
  • DRESS APPROPRIATELY-Wear long-sleeved shirts, long pants, and socks.

The severity and symptoms of WNV can vary widely. Approximately 80% of persons infected experience no symptoms, but up to 20% of persons can develop a mild illness, called West Nile fever. Fever generally resolves itself without treatment, but dangerous brain infections such as encephalitis or meningitis can develop in 1 out of 150 people. Symptoms of these diseases might include headache, rash, high fever, stiff neck, mental confusion, muscle weakness, tremors, convulsions, coma, and paralysis. Individuals who develop any of these symptoms should see their healthcare provider immediately.