The first horse, a 15-year-old Quarter Horse gelding, began showing clinical signs consistent with WNV on Oct. 7 and was confirmed positive on Oct. 12. His signs included anxiety and muzzle fasciculations (twitching). He had been vaccinated against WNV.

An 11-year-old Quarter Horse mare began showing clinical signs, which consisted of ataxia (incoordination) and muzzle fasciculations, the next day. Her vaccination status was not reported.

The third horse, a 15-year-old Tennessee Walking Horse gelding, first showed clinical signs on Oct. 17 and was confirmed positive on Oct. 21. His signs included ataxia and facial paralysis. His vaccination status was not reported.

All three horses are reported as 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.