Agriculture Commissioner Adam Putnam said Thursday that state officials, horse owners and veterinarians are taking strict precautions to contain the spread of the virus also known as EHV-1. It is not transmittable to humans.
He said six of seven confirmed cases have been linked to the horse show in Ocala in north-central Florida. The virus can result in neurological disease, respiratory disease, abortion and neonatal death in horses.
"We're all watching this, hoping it doesn't get bigger," Putnam said. "We've taken extraordinary measures to contain the spread."
Equine Herpes Virus, or EHV-1, is not a sexually transmitted virus. It's spread through respiratory secretions and via contaminated feed buckets, food, grooming tools and other equine equipment.
Rob MacKay, professor of large animal medicine at the University of Florida, said there are two different strains of EHV-1—one known as a "wild" strain and a second "neuro" strain that is far more contagious and deadly.
The affected horses in Ocala have the so-called "wild" strain, he said. But he added, "any time there's an EHV1 outbreak, that's potentially serious."
Six of the confirmed cases are linked to the "Horse Shows in the Sun" event in Ocala, a large hunter-jumper show, according to a Department of Agriculture news release. The state said it issued a quarantine for all of the horses at that show.
There are hundreds of horses at the show, which runs for nine weeks until mid-March. Competition is still ongoing, said Lindsay Yandon, a spokeswoman for the event.
"It was a joint decision between our management and state veterinarians," Yandon said. "It's less stressful on a horse to be out and showing and moving instead of in a stall all day. We wanted to give people that option. The vets recommended we give the horses that opportunity."
A seventh horse in the Wellington, Fla. area also was diagnosed as EHV-1 positive; officials say that horse has not had direct or indirect contact with any of the horses at the Ocala show.
The first affected horse in Ocala was taken to the University of Florida veterinary hospital in Gainesville on Feb. 20 after showing influenza-like symptoms, said MacKay. The horse is doing better and is still being treated at the hospital.
"The horse is slowly getting better," said MacKay, adding he hoped it would fully recover.
After five more horses at the Ocala show tested positive for EHV-1, state officials decided on the quarantine. Other areas where horses were exposed to the virus while at the Ocala show are also under quarantine; there are 12 such farms.
The United States Equestrian Federation said in a news release that established "protocols" for such competitions are important and are in place to safeguard horses brought in from different locations.
In Utah, the state State Veterinarian has issued several quarantines in Cache County following the confirmation of four cases of EHV-1, along with one other suspected case. According to a news release Wednesday, two of the five horses were euthanized. The cases in Florida and Utah do not appear to be linked.