As the first group of barns at the Fair Grounds Race Course near the end of their state-mandated equine herpesvirus quarantines, the Louisiana Department of Agriculture has been working to define the procedures which will allow those barns to be released from quarantine. Following a meeting earlier in the week between horsemen, USDA representatives, veterinarians, and outside advisors, those protocols have nearly been finalized.
According to assistant state veterinarian Dr. Dianne Stacey, any barn that has held a horse which tested positive for EHV-1, whether it be the wild strain or the neurogenic strain, is automatically quarantined for a period of 14 days. The horse which demonstrated the positive test is placed in isolated quarantine for 21 days; those with the wild strain are kept separate from those with the neurogenic strain.
In order to get out of quarantine, all the horses in the affected barn have to demonstrate two negative EHV-1 tests, spaced at least 72 hours apart, as well as undergo final checks by state veterinarians.
As of Thursday evening, there were a total of 10 horses on the Fair Grounds premises that had tested positive for EHV-1 (two for the neurogenic strain, the others for the wild strain), and six barns were under quarantine (14, 36, 47, 4, 30, and the receiving barn). Also on Thursday evening, the Department of Agriculture updated the Fair Grounds' voluntary quarantine of the entire backside to a mandatory one, meaning that still no horses are allowed to enter or exit the facility.
The state began the first round of tests on Thursday afternoon, beginning with the first three barns to have entered quarantine. Should the approximately 50 horses stabled in each of those barns all test negative for EHV-1, they would have to again test negative in 72 hours in order to be released from quarantine. If any of the horses test positive for either strain of EHV-1, the 14-day quarantine begins again.
“The rationale for testing has been to get the known positives out of the barn,” said Stacey. “We were under some logistical constraints with the holidays because of all the labs being shut down, which was why we didn't initially test. We've got a better handle now.
“The horses in the quarantined barns have been temped twice a day, every day, and we've removed everything that's even shown a hint of a fever (above 101.5 degrees). So in a perfect world, they'd all come back negative.”
Unfortunately, due to the nature of the EHV-1 virus and its ability to lie dormant in a horse's system, it appears unlikely that all 50 horses in each barn will be negative. One study found that four percent of a random sampling of 451 horses were positive for the EHV-1 virus (this study did not indicate whether “positive” meant latency or if the horse was actively shedding the virus).
Another study which looked at the necropsies of 132 broodmares indicated that 54 percent had EHV-1 in their lymph nodes (latent). Of those, 18 percent had the neurogenic strain. Of that 18 percent, close to 90 percent had the wild type as well. It adds confusion because horses can have both strains lying latently in their lymph nodes.
Dr. Nathan Slovis, director of the McGee Medical Center at the Hagyard Equine Medical Institute in Lexington, was hired as a consultant on the Fair Grounds outbreak and aided in developing the new protocols. He argues that even though a horse shows no symptoms, the virus' ability to lie latent may allow the horse to pass it on to its peers. Especially in a racetrack environment, in which horses are constantly in close proximity to one another, the Department of Agriculture has to do its job in order to prevent the virus from spreading.
“When it comes to regulatory agencies, herpes is herpes; it doesn't matter if it's wild-type or neurogenic type,” Slovis said. “Everybody keeps thinking 'oh, wild type, all horses have it, big deal, who cares.' And the majority of the time, wild type is not a big deal. It may cause abortions and you get some respiratory problems, but it can also cause the neurologic signs.”
The difference between EHV-1 neurogenic and EHV-1 “wild” type viruses is incredibly minute and requires a close look at each's genetic structure. The wild EHV-1 virus is considered the “normal” version of the virus, without any mutation. In the neurogenic form, a single element of the DNA is mutated; if nucleotide 2254 within the Open Reading Frame-30 gene has a guanine element instead of an adenine, the virus is neuropathic.
According to a study of 48 equine herpesvirus outbreaks over a 35-year period, 83 percent of the symptomatically neurological cases had the mutation, making the virus the neurogenic type. That means that 17 percent of the cases with neurological symptoms had the wild-type strain of the virus.
“It just goes to show you, the regulatory agencies have to take both seriously,” said Slovis. “Even though the majority of the time, the wild-type is going to be more of a nuisance factor, you can't take that risk at a big place like the Fair Grounds.”
A recent outbreak at the Los Angeles Equestrian Center, said Slovis, was an example of a group of horses with the wild type EHV-1 virus, but eight of the 15 positives at that facility demonstrated neurological symptoms, and one was euthanized. That outbreak lasted just over 60 days.
Local horsemen have expressed serious concerns about the protocols required to get out of quarantine. Many trainers in the affected barns operate small or mid-sized strings of horses, and being unable to race for that long would place them in jeopardy of going out of business. Already, the price of each herpes test has fallen on the horses' owners, and, at $53 apiece, that adds up.
Preliminary results from Thursday's testing at Barn 14, the origin of the EHV-1 outbreak, indicate 21 more positives for the wild strain of the virus.
“It's not going to fix itself in 14 days,” Slovis said. “I'm guessing it's going to be at least a 45-day process, but I don't expect any catastrophic events.
“Right now in New Orleans, none of those wild-type positive horses are showing neurologic symptoms. Which means they're just getting an upper respiratory infection, so they get isolated so that more horses don't get sick. These horses aren't going to die, they just don't want sick horses out on the premises so that they can continue racing normally.”
Along with the state-mandated biosecurity protocols implemented in the quarantined barns, the racetrack has begun to work on additional precautions to improve safety for the rest of the barns on the backside. Dr. Stacey said, among other protocols, the track is considering testing the pony horses for EHV-1.
“We had a consultant come in, and we had a risk analysis and a big discussion,” Stacey said. “It was suggested highly that they be tested because these ponies are under contract with different trainers, but then they go back to a common barn. We did do enhanced biosecurity with footbaths, etc., and we've been temping those ponies twice a day, but we did see that they were a little bit higher risk than some of the other quarantined barns. I believe that plans are underway to test them.”
Other measures already in place include disinfecting the starting gates between each race, having grooms bring their own buckets for their horses to the test barn, and not having the horse identifier touch the horses' lips in the paddock (the grooms are now asked to lift the lip in order to show the tattoo).
In the future, Dr. Stacey hopes the Fair Grounds will work with her department in order to open up another barn on the backside to allow horses to ship in for races, which would help to alleviate the small field sizes that have become prevalent since the outbreak began.
“The bottom line is that they're going to get over this,” Slovis summed up. “You may see a little spike before things calm down, but they've got procedures in place, are implementing additional precautions, and they'll get over this. It's just a matter of time.”
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