Two Idaho Horses Confirmed With WNV
WNV transmission occurs when infected mosquitoes feed on animals, as well as humans, after having fed on infected birds.| Photo: iStock
On Aug. 23, a 6-year-old mare was confirmed in Ada County. She presented on Aug. 22 with clinical signs that included recumbency (down and unable to rise) and hind-limb paralysis. She had been undervaccinated for WNV and was euthanized.

On Aug. 27, an 18-year-old Quarter Horse mare at a private facility in Payette County was confirmed after showing signs beginning on Aug. 24 that included lethargy, tachycardia (rapid heart rate), muzzle hyperesthesia (excessive sensitivity), facial and skin fasciculations (twitching), and tachypnea (rapid breathing). The mare, who was not vaccinated for WNV, is reported as recovering. Six additional horses in Payette County were exposed.

About West Nile Virus

WNV transmission occurs when infected mosquitoes feed on animals, as well as humans, after having fed on infected birds.

WNV Longform feature image
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Clinical signs of WNV in horses include:

  • Mild anorexia and depression
  • Fine and coarse muscle and skin fasciculation;
  • Hyperesthesia (hypersensitivity to touch and sound);
  • Changes in mentation (mentality), when horses look like they’re daydreaming or “just not with it”;
  • Occasional drowsiness;
  • Propulsive walking (driving or pushing forward, often without control);
  • Spinal signs, including asymmetrical weakness; and
  • Asymmetrical or symmetrical ataxia.

West Nile virus has no cure; however, some horses can recover with supportive care. Equine mortality rates can reach 30-40%. The American Association of Equine Practitioners includes WNV as one of the core diseases all horses should be vaccinated against at least annually.