On July 27, the California Department of Food and Agriculture confirmed there is no evidence of ongoing spread of equine herpesvirus at a show facility where a neurological case was reported earlier this week.

On July 25, a 6-year-old warmblood mare who had been stabled July 19-24 at the Sonoma Horse Park in Petaluma, California, tested positive for equine herpes myeloencephalopathy, a neurological form of EHV-1, and was euthanized. Three more febrile horses who had contact with the mare were tested for EHV-1, but only one tested positive.

Eighteen horses who were stabled with the euthanized mare at the  show grounds returned home to their Sacramento County barn on July 25 and are quarantined. The second horse to test positive was not on the grounds of the Sonoma County Horse Park and became neurologic on July 26. He was sent to an offsite veterinary hospital for treatment and is now confirmed negative for EHV-1. An additional horse at the home premises that did not attend the horse show presented neurologic symptoms on July 26 and left the premises for treatment. That mare was negative for EHV-1 and is currently stable.

A fourth horse, who was stabled in the same barn at the Sonoma Horse Park, presented with a fever and mild neurologic symptoms on July 24 and was sent offsite for treatment. That horse was confirmed negative for EHV-1, and the three remaining horses from his home barn left the premises and are quarantined.

“As of Monday, July 26, there is no evidence of ongoing EHV-1 spread at the Sonoma County facility following removal of all known affected and immediately exposed horses,” a CDFA release stated. “A complete facility quarantine will not be implemented there unless ongoing disease spread is confirmed.  The decision for individuals to attend an event at this premises within this timeframe should be discussed with their veterinarians and will be at the owner’s and/or trainer’s own discretion and risk.”

All affected horses were removed from the Sonoma Horse Park as of July 25 and horse showing has resumed with the HMI Equestrian Classic, which runs July 28-Aug. 1. All affected barns have been locked and disinfected and will not be used for at least seven days. Additional biosecurity measures, including twice-daily temperature checks for all horses on the grounds have been enacted.

The CDFA recommended that a horse attending any equine event be kept 30 feet away from other horses for at least seven days following the event.