In October 2012, EHV-1 first made the rounds in the news when several horses at Hawthorne Racecourse in Stickney, Illinois, tested positive for the neurological form of the virus and the racetrack was placed under quarantine. Although quarantine was lifted in January, the outbreak was a stark reminder of the fragile nature of horses and how quickly a serious virus can spread throughout barns and stables.
Since the racetrack and personal horse boarding are two different worlds, most everyday horse owners (like yours truly) were not very concerned about the EHV-1 outbreak at Hawthorne. A watchful eye was cast towards Hawthorne but not much else was done.
Then in late February, nearly 1,100 miles away from Hawthorne, another large-scale EHV-1 outbreak was reported at the Horse Shows in the Sun (HITS) show circuit in Ocala, Florida. Despite the great distance between Florida and Illinois, the HITS outbreak felt a little closer to home. Many show horses are also companion horses, and your everyday horse owner can--with lessons, money, and a little polish--take up showing with his or her companion horse. Most of these horses have permanent homes at show barns, but some do live at casual boarding barns. The line between the horse show world and casual boarding barn world is far more muddled than the line between the racetrack and personal horse ownership.
Then it happened. Rumors of EHV-1 in a Gurnee (Lake County), Illinois, boarding and show barn began circulating on Tuesday this week. Two horses had been euthanized after displaying neurological symptoms of the virus and confirmation of EHV-1 was pending a laboratory test. Several other horses at the same barn were also showing symptoms. The results came quickly: it was a confirmed EHV-1 outbreak. It was then reported that some of the horses from this barn had visited nearby stables for shows or clinics in recent weeks. Boarding and show barns all over the Chicago suburbs sat up and took notice. The smart ones conducted a voluntary lock-down, which means no horses are allowed to leave or enter the premises of the stable.
My barn is one of those conducting a voluntary lock-down, as Gurnee is about 45 minutes away. In my barn's case, absolutely no visitors are allowed. This includes outside trainers and farriers. Only veterinarians and individual boarders are allowed on the property until March 22, at least.
An excellent, comprehensive white paper by University of California at Davis on EHV-1 can be read here.
In summary, much like influenza in humans, there is no reversing the EHV-1 virus in horses. Sick horses must be isolated and provided with supportive care. Fever and respiratory problems develop first; neurological symptoms may follow. These include difficulty passing manure and urine, urine dribbling, loss of coordination in the hind legs (which may lead to the horse sitting in a dog-like position), and recumbency with an inability to rise. At this point, the virus has led to meningitis-like brain and spinal cord swelling. Once a horse is unable to stand again, euthanasia is the most humane step to take. Needless to say, it's a horrible way for any horse to pass.
In addition, the virus is highly contagious and can be spread as easily as the common cold. Horse nose-to-nose contact, sharing of tack and equipment, being in proximity to a sick horse and transmitting the virus on your person (clothing, shoes, hair, etc.) allow the virus to spread rapidly. Unfortunately, since it can incubate for up to two weeks, it is difficult to determine, in the early stages, which horses may be ill. This can prove problematic at racetracks and on large show circuits such as HITS--in some cases, horses become infected then do not begin displaying symptoms until they have left the racetrack or show grounds, making quarantine a challenge.
Horses should receive EHV/Rhino vaccines twice a year, and pregnant mares receive an additional vaccine to prevent foal abortion. However, these vaccines do not prevent the spread of EHV-1. Rather, they reduce the amount of virus-shedding, which lessens the chance of a vaccinated horse spreading the disease. EHV booster vaccines given during outbreaks do not prevent the spread of the virus and are meaningless, providing your horse already receives regular Rhino vaccinations.
With luck and diligence, the newest EHV-1 outbreak will be contained to the Gurnee stable. In the meantime, it's been reported that a horse euthanized at Santa Anita Racetrack in California has tested positive for EHV-1. Let's hope this remains an isolated incident.