When horses like those beauties above leave their peaceful pasture and are taken to the show ring to compete, the equine herpes virus most adult horses carry can spread due to the stress of competition. In an article by Jennifer Viegas of Discovery News, we read that Dr. Philip Johnson, who teaches equine internal medicine at the University of Missouri points out that “most adult horses are infected with the virus….[That] infection leads to a life-long association between the virus and its host. In most healthy horses most of the time, the host’s immune system prevents the virus from going active and being especially contagious.” But, he goes on, there are times when the virus overcomes the immune system and becomes active. An example is the April/May National Cutting Horse Association’s Western National Championships in Ogden, Utah: 32 cases of infectious equine herpes resulted, with those infected spreading the disease to other horses. Dr. Johnson says, “Congregated horses coming together to compete are stressed, adversely affecting the immune system’s function.” Dr. Johnson adds that it may be that show horses, that are commonly exposed to intense confinement and a lot of transport between shows, neither of which they may be used to, may become carriers of an activated virus. And the grouping of show horses closely together in temporary, strange stabling, is another factor. Once the virus is active, formerly unaffected horses can breathe in the virus, and are infected by horse workers’ hands, equipment, tack, and food.
The virus appears in two strains. One is more likely to cause neurological problems. The symptoms of the latter are fever of 102 degrees F or even higher; nasal discharge; fatigue; weakness; urine dribbling; leaning; tail loss of tone; and problems with standing. Dr. Bruce King, state veterinarian of Utah, says that an infected horse should be isolated, his temperature taken and recorded twice a day. Dr. John Hunt, Acting Arizona State Veterinarian, says further that this procedure should continue for 28 days after the initial symptoms are seen. If the sick horse has secondary infections, doctors may use anti-inflammatory drugs, antibiotics, and anti-viral drugs. If the horse can’t stand up, body padding and slings may be used; intravenous feeding and a catheter may also prove useful.
Viegas concludes that “some vaccines provide protection against the less debilitating form of the virus, but they do not appear to protect against the neurological syndrome.”