EHV cases reportedly on the rise

EHV cases reportedly on the rise

Outbreaks temporarily close tracks, trigger quarantines in four states
Mar 01, 2006

NATIONAL REPORT — An increase in the number and severity of equine herpesvirus Type-1-induced neurological disease outbreaks has forced the closure of racetracks, the quarantine of several barns in least four states this year and the humane destruction of several horses.

The most recent scare at presstime involved a horse at Bowie Training Center in Maryland; 29 horses were quarantined after one, previously treated for protozoal myeloencephalitis, continued to display neurologic signs consistent with the herpesvirus outbreaks. A collective sigh of relief from around the state was echoed when the tests came back negative Feb. 5, and no new cases had been reported in the state for two weeks at presstime.

The question remains: Has increased awareness and improved diagnostics facilitated the recognition of the infectious disease, or do real increases exist?

"Certainly we do feel that within the last few years, there has been an increase in the number of outbreaks of the neurological form of the disease in North America (United States and Canada)," says David Powell, BVSc, FRCVS, equine epidemiologist with the University of Kentucky Gluck Equine Research Center. "Previously, the number of neurological outbreaks that were reported were quite rare — one a year or even less than that. Within the last three years, we have seen an increase in the number of outbreaks in the neurological form of the disease in various parts of the country and in various breeds of horses. It doesn't seem to be restricted to any particular group."

Maryland has been plagued with numerous EHV events beginning with Pimlico Race Course, where three horses were euthanized in January; a fourth was destroyed at Laurel Park, and another horse was put down at a Kent County farm.

A total of 12 horses were either euthanized or isolated in three barns at the home of the Preakness. The Maryland Jockey Club proactively placed the Baltimore oval on quarantine on Jan. 21, restricting the movement of horses. Barn 9 at Laurel Park was under a hold order from the Maryland Department of Agriculture, but no new cases had been reported there for two weeks.

DVM Newsbreak
"Conditions at Pimlico and Laurel continue to progress in a positive manner," Maryland State Veterinarian Dr. Guy Hohenhaus said Feb 1. The hold order at Pimlico had just been lifted at presstime.

That didn't dissuade nearby Charles Town Races & Slots in West Virginia's panhandle from quarantining its facility to stave off the spread of equine herpesvirus Type-1 (EHV-1) in early February. Horses are not permitted to enter the facility, which houses more than 1,500 animals, and no animals will be permitted to return should they leave for another race. The duration of the preventive protocol was undetermined at presstime, but typical quarantines last about 21 days, including a thus-far successful movement ban at Turfway Park in Florence, Ky., where two horses were euthanized in mid January; the Kentucky outbreak, which also affected Western Kentucky Training Center 200 miles away, began Jan. 2. No new cases had been reported more than three weeks later, according to Kentucky State Veterinarian Dr. Robert Stout, and plans to lift the movement ban from the general population was anticipated in early to mid February.

"The catch word is biosecurity," Stout says. "I don't think you can ever do enough in terms of biosecurity."

Experts recommend the quarantine of at least 21 days with no new cases before reintroducing horses that might have been exposed to infected horses. The isolated horses should have their temperature taken at least once a day during that period to keep tabs on the possible spread within the isolation barn.