West Nile Virus in California

The Kern County horse marks California’s first confirmed case of WNV in 2022.
Share
Favorite
Please login

No account yet? Register

ADVERTISEMENT

Map of California highlighting Kern County
This case marks California’s first confirmed horse with WNV in 2022. | Wikimedia Commons

On July 13, the California Department of Food and Agriculture confirmed a 6-year-old unvaccinated Arabian cross gelding in Kern County, California, positive for West Nile virus (WNV). He presented with acute recumbency (down and unable to get up), grade 3 out of 5 ataxia (incoordination), hyperesthesia (hypersensitivity to touch and sound), knuckling, and severe abrasions on his hocks and fore fetlocks, but did not have a fever. The horses is affected and alive, and the boarding facility where he resides is not currently under quarantine.

This case marks California’s first confirmed horse with WNV in 2022.

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

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 (involuntary twitching);
  • Hyperesthesia (hypersensitivity to touch and sound);
  • Changes in mentation (mental activity), 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.

West Nile virus 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. It takes several weeks for horses to develop protection against the disease following complete vaccination or booster administration.

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 insect feeding times (typically early in the morning and evening); and

Applying mosquito repellents approved for equine use.

Brought to you by Boehringer Ingelheim, The Art of the Horse

Share

Written by:

Sign Up for EDCC Health Alerts

Don’t miss an important EDCC Health Alert! Get alerts delivered straight to your inbox by signing up for The Horse’s newsletter.

"*" indicates required fields

Name*

Additional Offers

Weekly Newsletters
Monthly Newsletters
Other Newsletters
This field is for validation purposes and should be left unchanged.

More Alerts

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from TheHorse.com

Sponsored Content

Weekly Poll

sponsored by:

How do you prevent gastric ulcers in horses? Please check all that apply.
147 votes · 346 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with TheHorse.com!