Equine herpesvirus outbreak: Veterinarians confirm 17 cases at two California locations

RIVERSIDE, CALIF. — Veterinary officials confirmed a single case of the neuropathogenic strain of equine herpesvirus (EHV-1) infection at a Riverside County ranch. The finding follows confirmation of 16 other cases recently in nearby Orange County.

The Orange County outbreak began Jan. 11, with a gelding displaying neurologic signs, according to the California Department of Food and Agriculture (CDFA). The gelding was later confirmed positive for the neuropathogenic strain of EHV-1 infection. The horse was isolated, quarantined and placed under veterinary care.

Emerging from the shadows: Cases of equine herpesvirus continue to crop up in southern California. (Getty Images)

That horse is the only one of the now 16 cases at the facility that displayed neurologic signs, and CDFA officials say the horse is now recovering. Other confirmed cases have displayed respiratory signs, limb edema and/or fever. One of the horses was euthanized because of recumbency, but a necropsy indicates it is "highly unlikely" the condition was caused by the EHV-1 infection.

CDFA officials were not available at presstime to offer further details about the ranch and the number of horses under observation.

CDFA officials did report that the Riverside County case was confirmed Jan. 24 in a gelding displaying clinical signs associated with equine herpesvirus including hindlimb incoordination and urine dribbling.

Veterinary officials have quarantined both premises, but say they are not aware of any links between the EHV-1 cases emerging between the two facilities. Epidemiologic investigations are underway.

CDFA says the source of the outbreak has yet to be identified, but the initial investigation reveals no link to three outbreaks in 2011—one in May that sickened nearly 90 horses across 10 Western states and two other smaller outbreaks later in the year.