Neurologic Equine Herpesvirus at California Boarding Facility

An aged Quarter Horse mare was confirmed positive for neurologic herpesvirus in Santa Clara County, California.
Santa Clara County California map

An aged Quarter Horse mare was confirmed positive for neurologic herpesvirus in Santa Clara County, California. iStock

UPDATE April 7, 2021: As there were no additional cases for fourteen (14) days on the home premises, the quarantine was released.

The California Department of Food and Agriculture (CDFA) reported a confirmed case of neurologic equine herpesvirus at a boarding facility in Santa Clara County. The 21-year-old Quarter Horse mare was confirmed with EHV-1 on March 23 after exhibiting clinical signs that included ataxia, painful neck and proprioceptive deficits in the hind end. The mare was affected and alive at the time of this report.

The mare is being treated in isolation at a veterinary hospital. 

The home premises has been quarantined with enhanced biosecurity measures in place and twice daily temperature monitoring. The clinical horse has no recent travel history and no links to any other EHV-1 cases. 

The home premises hosted an event on March 21, and one asymptomatic horse from the home premise competed in an event from March 19-21. Event managers have been notified and are encouraging all owners of potentially exposed horses to perform twice daily temperature monitoring, limit movement, and practice enhanced biosecurity measures for the next 14 days. 

91 horses were considered exposed.

CDFA will be onsite and continue to actively monitor exposed horses. For more information about neurologic herpesvirus (also called equine herpesvirus myeloencephalopathy or EHM) download this fact sheet.  

Information for this report was provided by the Equine Disease Communication Center.

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