Michigan Horse Test Positive for West Nile Virus

Michigan Horse Test Positive for West Nile Virus

A viral disease, WNV is transmitted to horses by infected mosquitoes.

Photo: Photos.com

The Michigan Departments of Agriculture and Rural Development (MDARD) and Community Health (MDCH) have confirmed that an 8-year-old horse from Grand Traverse County tested positive for West Nile virus (WNV) and was euthanized after failing to respond to treatment and supportive care.

The gelding was not vaccinated against WNV. The other horses residing at the affected horse's premises have since been vaccinated against the disease. The MDARD was also recently notified a small turkey flock in Ingham County was affected by WNV, with high death losses due to the disease.

“The virus has affected poultry in the past,” said state veterinarian James Averill, DVM, PhD, “and both of these unfortunate losses stand as reminders that we should all be diligent about vaccinating our horses, using mosquito repellent, keeping water troughs fresh and clean, and emptying any containers of water not intended for animal use.”

Matthew Davis, MD, MAPP, chief medical executive of the MDCH, added, “Anytime we find West Nile Virus in animals, this serves as an opportunity to remind people that they also need to take precautions to protect themselves from mosquito bites. While we have not had a positive human case so far this season, we do know that it is circulating in the environment so residents should take precautions to protect themselves and their families.”

In addition to vaccinating horses against WNV, the following mosquito control measures should be utilized:

  • Use insect repellents, following label directions;
  • If possible place horses in barns or stables under fans during dusk, dawn, and other times when mosquitoes are present;
  • Eliminate mosquito breeding areas, including wet areas of pasture; 
  • Fill in puddles;
  • Repair gutters and down spouts to prevent pooling around building foundations;
  • Empty containers that might hold small pools of water where mosquitoes can breed; and
  • Empty and refill water tanks once or twice weekly.

Health Alert: West Nile Virus

Additionally, consider control of mosquitoes in ponds and large water containers through the use of larvacides and fish.

A viral disease, WNV is transmitted to horses by infected mosquitoes. Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional drowsiness; propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia (incoordination). Equine mortality rate can be as high as 30-40%.

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