Two Utah Horses Contract WNV

The Utah state veterinarian has reported two recent equine West Nile virus cases. The first, a horse from Weber County, was described as affected but alive on Oct. 1. The second, a Utah County horse reported on Oct. 2 as recovering, is an unvaccinated 16-year-old Quarter Horse gelding. He began showing clinical signs on Sept. 15, and veterinarians confirmed him positive Sept. 25.

About West Nile Virus

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

Clinical signs of WNV in horses include:

  • Mild anorexia and depression;
  • Fine and coarse muscle and skin fasciculation (twitching);
  • 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 (incoordination).

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.