California Vets Provide EHV-1 Update, Offer Prevention Advice


While one barn at Los Alamitos remains under quarantine due to equine herpesvirus-1 positives, the situation in California appears to have calmed down considerably. Dr. Rick Arthur, the California Horse Racing Board equine medical director, brought listeners up-to-date during a meeting Tuesday at Santa Anita.

Speakers at the meeting, which not only attracted horsemen from the racetrack, but also from local horse show barns and boarding facilities, included Dr. David Wilson of the University of California at Davis and Dr. Kevin Hankins from Fort Dodge Animal Health. Fort Dodge sponsored the series of meetings, which began with one for veterinarians Monday night at Santa Anita and was to continue Tuesday night with a veterinarian meeting at Golden Gate Fields followed by one for horsemen at Golden Gate Wednesday at 10:30 a.m.

Arthur said that in addition to the horse who showed neurological signs of EHV-1 at Los Alamitos and is recovering, four other horses in that barn had fevers. One fever turned out not to be due to the disease; one horse tested positive and showed some respiratory signs of the illness; one tested positive for the neurological strain but showed no clinical signs; and the fifth was being tested on Tuesday.

Initially, Royal Brass at Golden Gate Fields in Northern California developed neurological symptoms of EHV-1 in late December, prompting a quarantine at Golden Gate, Bay Meadows, and Pleasanton that has since been lifted. Royal Brass has recovered and has been returned to Golden Gate from U.C. Davis, where he had been treated. Like Royal Brass, the horse at Los Alamitos in Southern California did not appear to have come into contact with any at-risk horses.

“There were two Arabians that shipped in from Delaware about 2 1/2 weeks previously that have not had any evidence of EHV-1,” Arthur said. “So we don’t know what the source of that was. The horse that did become neurological had been there (at Los Alamitos) for about 60 days.”

Wilson explained that horses can be exposed to EHV-1 as youngsters and then the virus can become dormant.

“Because it’s dormant, in some point in some horses, it reactivates, starts to multiply, and that horse could potentially get sick from that reactivated virus,” Wilson said. “So you don’t necessarily have to have new horses coming into the environment to set off herpes.”

Wilson said that veterinarians don’t yet know what prompts such reactivations, but that stress could be a trigger. Still, because nose-to-nose contact between horses is the most direct way to pass the virus and because new horses incubating the disease can infect others, he recommended isolating newcomers for three weeks if possible. He also discussed hygiene recommendations to help reduce the risk.

“When faced with something like this, the immediate thought is what’s the best vaccine to use,” Wilson said. “The immediate thought should be, ‘How do I prevent these transmissions?’ There is no vaccine against any disease that is as good as basic hygiene.”

Questions from the audience at the meeting arose about how to handle a situation where a horse leaves a barn to go to another racetrack or a show and then returns, having potentially come into contact with at-risk horses. If it is not convenient to isolate those horses, Hankins recommended placing a ribbon or chalk mark on their stalls, indicating that they should be fed, groomed, and handled last.

Wilson advised limiting nose-to-nose contact between these horses and the others at the facility for as long as possible. He also said that horses should have separate feeders and that people handling the horses should wash their hands between horses or use disposable gloves.

“At the racetrack it’s fairly common practice for grooms in particular to carry rags in their back pocket and wipe off this horse’s nose and that horse’s nose,” Wilson said. “That is a very efficient means of transmission. Another potential is a bit that is pulled off of one horse and put into the next horse without being washed.”

All three veterinarians recommended taking temperatures twice a day as a good way to spot not only EHV-1 early, but many other infectious diseases. However, Wilson added that it is easy to let concern for a relatively rare disease grow out of proportion to its incidence.

“Many more horses die of colic than die of equine herpesvirus,” he said.