Three cases of non-neurologic EHV-1 were confirmed Feb. 11 at the Desert International Horse Park in Thermal, California, horse park officials announced last week. An additional two cases from the same barn and a fourth case from a different barn on the property have since been confirmed (see updates below).

“The three horses were immediately quarantined and are under bio security restrictions,” a press release from the horse park stated. “Representatives from the State of California Veterinary Office have been involved in all decisions being taken. The one tent where the three horses were located is now under mandatory quarantine. All other operations of the horse show are cleared to continue to operate. All three horses are under veterinary care and are doing well.”

The California Department of Food and Agriculture said one horse was confirmed Feb. 11 with equine herpes myeloencephalopathy (EHM) secondary to EHV-1 (non-neuropathogenic strain) and two additional febrile-only cases of EHV-1 infection also were confirmed in horses from the same barn.

CDFA recommends that all horses currently stabled at the horse park have temperatures monitored twice daily and veterinarians immediately notified of any fevers over 101.5 degrees or any neurological symptoms. CDFA additionally recommends that any horses not under quarantine who are leaving the showgrounds be isolated from other horses and have their temperatures monitored twice daily for at least a week.

“We are working closely with the CDFA and the USEF on all elements of our program,” the horse park press release stated. “All three horses were immediately isolated and are doing well under the care of veterinarians. Tent 34 remains isolated and additional biosecurity measures, including fencing, will be in place [Saturday] morning. We appreciate your continued support as we work through this situation. We will proactively communicate any relevant updates. We will proactively communicate any additional relevant updates. If you have any questions, feel free to contact us through info@deserthorsepark.com.”

The horse park currently is in the middle of its winter season and is hosting the Desert Circuit IV show, which included the $50,000 Butet USHJA International Hunter Derby on Friday and continues with the $40,000 Adequan Grand Prix today.

Update 1: Horse park officials announced on Feb. 15 that two more horses stabled in Barn 34–where the index cases were located—tested positive. Those horses will be retested Feb. 16.

Four additional horses from three other barns on the property presented with elevated temperatures, and all tested negative.

“We have begun testing of the three horses [already] in isolation,” a release from the horse park stated. “All are doing well, without symptoms, and one has already tested negative. The other two will be retested in two days [Feb. 17]. We have had no new reported horses with elevated temperatures, or other clinical symptoms, in the horse park since Monday morning at 8 a.m.”

Update 2: On Feb. 17, horse park officials announced one additional case of confirmed EVH-1. The horse, who is from a different barn than the five above, had a fever on Friday, Feb. 11, and tested negative then. However, a subsequent test administered two days later (Feb. 13)—a broader respiratory panel that also included EHV-1—came back positive for EHV-1 on Feb. 16. That horse, whose temperature has returned to normal, has been placed in isolation and the barn it came from, Barn 6, from placed under quarantine.

“The strain of EHV-1 thus far has resulted in relatively mild symptoms, and horses are recovering quickly,” the U.S. Equestrian Federation said in a press release. “Adherence to USEF’s EHV-1 vaccination requirement has also very likely contributed to reduced severity of clinical signs.”

For additional perspective, USEF veterinarian Stephen Schumacher said, “With EHV, it’s not a matter of ‘if’ but a matter of ‘when’. Most important is the identification and isolation of sick horses. USEF has been in constant contact with competition management at Desert International Horse Park and with CDFA during the current EHV situation. We are very supportive of the efforts of competition management and of the veterinarians of the CDFA, and are encouraged by the steps being taken to mitigate the spread.”

All five cases from Barn 34 were reported to be doing well and asymptomatic as of Feb. 17.