At Sundance Ranch in Redlands, owner Janet O'Connor isn't taking any chances with the 120 horses she boards at her 30-acre facility.
"Nothing is coming into this ranch right now. Absolutely not," O'Connor said.
O'Connor put a temporary hold on all horses coming and going from her stables. It came after news that an outbreak of neurological equine herpes virus was circulating in the horse community.
"In the last 10 days to two weeks, a lot of people have canceled a lot of events and people are staying home," she said. "Better safe than sorry."
The virus can lead to respiratory illness, neurological problems and paralysis in horses. It's not only highly contagious - it can be deadly.
"There isn't a treatment for this particular strain," said John Welsh of the Riverside County Animal Services. "It is relatively powerful so it's something that can catch horse owners off guard."
There are 18 known cases of equine virus in California. The state has quarantined infected horses in 12 counties in hopes of stopping the virus in its tracks. None of the infected horses are within San Bernardino or Riverside counties.
Still, ranch owners say they are using an abundance of caution when it comes to caring for their horses.
The outbreak has been traced back to a horse cutting competition in Utah earlier this month.
At least three dozen horses that participated in the event have come down with the illness.
"I am just telling all my clients that I'd rather you not go out," O'Connor said. "If you do go out, there is a possibility that you may have to go somewhere else or we have to quarantine your horse away from everybody else for 10 to 14 days."
Horse owners are keeping a tight rein on their horses until the worst is over.