The neurologic strain of herpes can be devastating, though.
"When it gets to the point where the horse is falling and can't get back up, then recovery from that is rare and often leads to euthanasia," said Lunn, who is also on the faculty at Colorado State. "In the case where it can be spread from horse to horse, it can be a great threat to the horse industry."
The type of quarantine and preventive protocols being used by the Maryland Department of Agriculture are the most effective ways to control the disease, Lunn said.
The more severe strain of equine herpesvirus attracted attention in a 2003 outbreak at Findlay College in Ohio. There was another high-profile outbreak associated with the Florida town of Wellington, a center of equestrian activity, in late 2006.
Before 2003, outbreaks of neurologic EHV-1 were sporadic. However, in 2005, there were six reported outbreaks in four states, and in 2006, the instances climbed to 11 reported outbreaks in eight states, according to a report by the U.S. Department of Agriculture.
The increased activity has prompted the federal agriculture department to describe the more serious equine herpesvirus as "an emerging disease," and the condition is now attracting a great deal of investigation, according to Lunn.
"What it means, only time will tell," Lunn said. "It may be that the increased occurrence will simply go away ... but there also is the possibility that the disease is changing."
