A barn in Ventura County, California has been quarantined after a mare developed neurologic signs associated with Equine Herpesvirus-1 (EHV-1), according to information supplied by the Equine Disease Communication Center (EDCC).

The 13-year-old Quarter Horse mare is in isolation at a local veterinary clinic for treatment while 32 potentially exposed horses at her home barn have been quarantined with extra biosecurity measures put in place. No additional cases have been identified as of this time.

The mare developed trouble urinating in late November and soon after developed a fever and a urinary tract infection. By December 2 she had become ataxic and she tested positive for EHV-1 on December 5. 

EHV-1 most often causes mild-to-moderate respiratory illness (rhinopneumonitis), but the infection occasionally leads to the life-threatening neurologic disease EHM. The mechanisms through which EHV-1 produces neurologic disease are not yet understood.

While the affected mare was vaccinated against EHV-1, according to the EDCC, there is no vaccine that specifically protects against EHM, so biosecurity is a crucial part of prevention. EHV-1 spreads from horse to horse through nasal discharge or aerosol droplets. Humans can spread the virus via contaminated hands, clothing and equipment. 

To learn more about EHM and how you can protect your horse, click here.