Ten horses in California have a highly contagious and potentially fatal disease, state agricultural officials said Tuesday.
The horses tested positive for equine herpes virus, or EHV-1, and have been found in five counties: Kern, Placer, Stanislaus, Amador and Napa.
California is among five Western states and Canada that have found the virus in horses. Including the horses in California, 17 horses have tested positive nationwide.
So far, only a horse in Kern County was euthanized after showing severe neurologic signs often associated with the disease. The others have been quarantined. The disease can spread quickly among horse populations but cannot be passed to humans.
Officials with the California Department of Food and Agriculture said all of the infected horses attended the National Cutting Horse Association's Western National Championships in Ogden, Utah, from April 30 to May 8 where they were most likely exposed to the virus.
CDFA staff have contacted all 54 exhibitors from California who participated in the Ogden event and asked them to isolate and monitor their horses for signs of EHV-1.
A temperature in excess of 102 degrees commonly precedes other signs, including nasal discharge, lack of coordination, weakness in the horse's hind quarters and lethargy.
State officials said there is no equine vaccine to protect against the virus.
As news of the outbreak spreads, so does the concern among horse owners.
Veterinarian Troy Ford of Clovis received about 60 phone calls from his clients on Monday and about 30 more calls as of Tuesday afternoon.
"People are worried," Ford said. "They want to know what the risks are to their horses."
Ford said outbreaks of EHV-1 are not unusual and that the best way to prevent the spread of the disease is keep horses apart.
As a precaution, Carol Anderson Ward, owner of the Murieta Equestrian Center, suspended all events at her Rancho Murieta facility for 21 days.
"For us the most important thing is to stop the spread, so we have decided to shut things down," Ward said.
Organizers also are canceling horse shows, festivals and classes in Texas, Utah and elsewhere in an effort to stem the disease's spread.
The outbreak has horse owners across the West worried, said Preston Skaar, president of the Idaho Cutting Horse Association.
"It's a hard deal, but all you can do is have your horses stay home and wait it out," Skaar said.