Approximately 300 horses remain quarantined and one has been euthanized since a dangerous virus broke out at the L.A. Equestrian Center in early November.
Known as the equine herpes virus, its symptoms are similar to the flu: high temperatures, lethargy, breathing problems. More severe cases are rare but they can cause incoordination as well as abortions in mares.
"It's a very common virus in the horse population. It has been around for years and years and years," Kent Fowler, the animal health branch chief for the California Department of Food and Agriculture, tells KPCC.
State authorities get involved when at least one horse exhibits neurologic symptoms, like being unable to control its footing.
In extreme cases, an animal might not be able to stand up. That's what happened to the horse that had to be put down on November 3, Fowler explains.
The equine herpes virus is typically passed between horses by nose to nose contact. It can also be transmitted by humans who work with an infected animal without properly disinfecting their clothes or hands.
Because the virus is highly transmissible, strict biosecurity procedures are in place at the L.A. Equestrian Center, where six barns housing approximately 75 horses each are under quarantine.
These days, trainers, groomers and other staffers who clean stalls and feed horses are wearing hazmat suits over their clothes, disposable booties over their shoes and latex gloves. They don't walk from barn to barn and they disinfect their shoes and hands when they're done.
Missy Bennett, who lost her horse to the virus, described to our media partner NBC 4 the extreme measures owners are taking to protect other animals: "We decontaminate our shoes by brushing off dirt. And then we put our feet in a 10% clorox solution to disinfect our feet."
Everyone is also being asked to take their horse's temperature in the morning and at night. Compliance has been very good, according to Fowler.
"A lot of biosecurity is common sense. Don't use the same tack or the same halters. Don't have common water troughs. [Horses shouldn't be] sharing feed or water," he says.
Only the west side of the Equestrian Center has been affected by the outbreak. The east side remains free of the virus and is operating as normal.
Fowler sees signs of progress. As of Thursday, the Equestrian Center had gone two days without any new cases. After the last confirmed case of the virus, barns will remain under quarantine for 14 to 21 days.
"Every day we go without any new cases," Fowler says, "is very much an optimistic happening.