WNV in Ohio

A third horse in Holmes County, Ohio, has tested positive for West Nile virus (WNV), the Equine Disease Communication Center reported. This is the eighth confirmed case of WNV in Ohio horses thus far in 2018, according to EDCC data.

“A 16-year-old pony mare began showing signs on Aug. 25, including abnormal gait and refusing to bear weight,” the EDCC said. “On Aug. 27, the emergency equine veterinarian was called out. Upon arrival the veterinarian noticed that the pony was laterally recumbent, tachycardic (increased heart rate), and had a fever of 105.8°F.

“Blood was drawn for testing and the owner opted to euthanize the animal,” the EDCC continued. “The sample was submitted to the University of Kentucky Veterinary Diagnostic Laboratory on Aug. 29 and tested positive for West Nile Virus by IgM capture ELISA testing on Aug. 31.”

In 2017, officials confirmed 14 cases of WNV in Ohio horses, according to USDA Animal and Plant Health Inspection Service data.

WNV 101

West Nile virus is transmitted to horses via bites from infected mosquitoes. Not all infected horses show clinical signs, but those that do can exhibit:

  • Flulike signs, where the horse seems mildly anorexic and depressed;
  • 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); and
  • Spinal signs, including asymmetrical weakness; and
  • Asymmetrical or symmetrical ataxia (incoordination).

West Nile has no cure, however some horses can recover with supportive care. Equine mortality rates can reach 30-40%.

Studies have shown that vaccines can be effective WNV prevention tools. Horses vaccinated in past years need an annual booster shot, but veterinarians might recommend two boosters annually—one in the spring and another in the fall—in areas with prolonged mosquito seasons. In contrast, previously unvaccinated horses require a two-shot vaccination series in a three- to six-week period. Full immunity takes several weeks to achieve.

In addition to vaccinations, owners should work to reduce mosquito population and breeding areas and limit horses’ mosquito exposure by:

  • Removing stagnant water sources;
  • Dumping, cleaning, and refilling water buckets and troughs regularly;
  • Keeping animals inside during the bugs’ feeding times (typically early in the morning and evening); and
  • Applying mosquito repellents approved for equine use.