As most of Aiken's horse people have probably heard, an outbreak of equine herpes virus (otherwise known as rhinovirus) has shut down many equestrian activities in Florida. The virus appears to have been introduced by a group of horses imported from Germany to the USDA Animal Import station in New York and then shipped by van to Wellington. To date, eleven horses have been confirmed with the disease. Five have died or been euthanized; four in Wellington and one in Ocala. The majority of cases occurred in Wellington, with one in Jupiter and one in Ocala. All infected animals had contact with horses in Wellington.
(Read a recent article about the outbreak in the Palm Beach Post here. Or check out the December 16 press release from Phelps Media Group. )
Rhinoviruses are quite common. In fact, a little more than 50% of human common colds are caused by rhinoviruses. It is widely believed that the human common cold actually "jumped" from horses to people not long after horses were domesticated.
In horses, the most common strain of rhino (EHV-1) causes low fevers and respiratory symptoms as well as spontaneous abortions in broodmares. Another strain (EHV-4) can cause higher fevers and thick nasal discharge. Recently, EHV-1 seems to have mutated into a far more virulent disease. This dangerous strain of rhino infects the horse's brain and spinal cord, causing neurological symptoms. These symptoms can be mild or severe. Horses that lie down and cannot get back up are generally euthanized.
(Here's what the Merck Veterinary Manual has to say.)
Rhino is an airborne virus that can spread as far as 35 feet from a sneezing horse. Vaccinations are available (in fact, most show horses already get regular flu & rhino vaccines) but the neurological form of the disease does not seem to be prevented by currently available vaccinations. (A modified live virus [MLV] vaccination might be more effective. Read about it here.) Today in Florida, many barns have set up elaborate sterilization procedures to try to prevent further spread of the illness.
So should you go to Florida with your horses? Some Aiken polo players and few show riders have decided to cancel their Florida seasons. Others are waiting for the outbreak to pass. To date, there is no official statewide quarantine, although barns where herpes has been confirmed or is suspected are under state or voluntary quarantine (eight as of this writing. See them on a map.) The general consensus is that the virus has probably been contained and that shipments to uninfected barns after Christmas are probably safe. The latest news is available at the Florida Association of Equine Practitioners website.
This is the second major neurological herpes outbreak this year. The first one, which ran from January to March, claimed a number of horses at Pimlico racetrack in Maryland and sickened horses from Kentucky to Wisconsin. (Read about it here.)