Graves County, Kentucky
The Graves County pony was not vaccinated against the disease. | Photo: Wikimedia Commons

On Sept. 27, Kentucky officials confirmed a 12-year-old pony gelding in Graves County with West Nile virus (WNV). The pony, which was unvaccinated against WNV, began experiencing clinical signs on Sept. 16. Signs consisted of muscle fasciculations (twitching) and unsteadiness. He is reportedly recovering

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;
  • 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.