The Breeders’ Cup Forum: Coping with EHV-1
Dr. Dawn Folker-Calderon has been the Illinois Racing Board's state veterinarian at Thoroughbred racetracks since 2006. A 1998 graduate of the Iowa State University College of Veterinary Medicine, Folker-Calderon interned at San Luis Rey Equine Hospital in Bonsall, Calif., then operated a private Standardbred practice for more than six years.
Folker-Calderon has been on the front lines of Hawthorne's battle against an outbreak of the deadly equine herpesvirus-1 myeloencephalopathy, which hit the Chicago-area track in October and claimed its sixth horse last Friday. The disease has led to the establishment of bio-security protocols, including quarantine barns, segregated training hours, and a partial ban on travel (some horses were allowed to leave the stable area provided they went to a quarantine facility). Other racetracks have imposed a ban on any horses shipping in from Hawthorne until further notice.
EHV-1 can spread one of several ways, most notably through horses inhaling viral particles from infected horses that are nearby. Humans, who do not get the disease, can carry it from horse to horse via clothing, hands, tack, etc.
When was the latest case of EHV-1 diagnosed?
The latest case of a horse showing neurological symptoms was Dec. 1. The horse was isolated and testing confirmed that it was EHV-1.
What does that mean for the end of the quarantine period if no other horses are stricken?
We're looking at the end of December (28 days after the last horse shows neurological symptoms of the virus).
When the first horse showed symptoms in Oct. 14, where did the protocols come from that were imposed at Hawthorne?
Protocols were from Illinois Department of Agriculture and Kentucky's Department of Agriculture. We worked with Kentucky because we've never really had to deal with an outbreak like this in Illinois before.
What resources are being used to deal with this?
I've spoken with numerous internal medicine specialists, along with specialists in the lab that we are doing testing through (IDEXX Laboratories in Sacramento, Calif.).
What makes this disease so pervasive and difficult to control?
One thing is that sometimes the only symptom is a fever. It can be a very short-lasting fever and might not even be caught through the twice daily temperature readings. That might be the only symptom and it can be missed.
Most horses are exposed to the equine herpesvirus as foals alongside their mother. The regular strain can mutate into the neurological strain. There is no vaccine for the neurological form.
Is there any way to identify the source of this outbreak?
No, we haven't able to trace it to a specific horse.
Is this a familiar strain of this virus?
From the histories I'm getting it's not been a textbook strain. A lot of these horses have never had a fever, and then suddenly they go down in their stalls. They've shown no previous neurological symptoms. That makes it extremely difficult.
Has there been any pattern as to which horses exhibited the neurological symptoms. For example, have you been able to separate which horses had primary versus secondary exposure?
We've had 12 neurological horses; five were from the barn where it was first reported. But I think we may probably have had it in a few barns before anyone realized it was in that first barn.
One of the hardest things in controlling this is the barns are very close together. Other tracks that have dealt EHV-1 had nearby farms, fair grounds, or abandoned tracks where horses that tested positive can be moved. We didn't have that as an option. We were able to move horses out of barns to make isolation areas to keep the EHV-1 horses as far away as possible.
Are tracks that have banned the shipment of Hawthorne horses to their stable area – even after the quarantine period is over – overreacting?
At first I thought maybe. After going through this, though, I wouldn't wish it on anybody. After this is all over with at Hawthorne, I am hoping the other tracks will reconsider their positions. I can understand, though I do think there might be some slight overreaction.
With the benefit of hindsight, should anything have been done differently (i.e., set up isolation barns for claimed horses) at the outset?
We set up the only isolation areas we were able to, so I couldn't do anything differently. I looked into the claiming rules, so I couldn't change that, either. We didn't have any room for a separate barn for claimed horses.
What's been the reaction of horsemen?
The majority have been good. I think a lot of them didn't think it was going to get to their barns, even though we discussed biosecurity measures, hygiene, and even went out with a bilingual vet technician and explained to their stable help what needed to be done to prevent the virus from spreading A lot of them didn't think it was going to happen. This is everyone's problem and it takes teamwork to deal with it.