Many breeders and mare owners are working to inform themselves more on this disease, as the devastating effects are being felt by those who haven't checked to see if their mares or stallions have been vaccinated against this disease that causes abortion in mares. In fact, even the American Quarter Horse Association is willing to keep EVA vaccination records on hold with the horse's permanent records. This disease has been given little attention until now and many mare owners may not know exactly what the effects are of the disease.



EVA is an acute upper-respiratory tract infection that is caused by a specific herpes virus. The disease has been known about for many years, but has not always been given the attention that it requires. The disease came into the spotlight a little more when an outbreak occurred in Thoroughbreds in Kentucky in 1984. The disease was mistaken for influenza and Rhinopneumonitis because the symptoms are so similar. The horse will develop a fever and nasal discharge as it would in these two conditions.

This disease, however, is more serious to the mature horse, especially broodmares. All ages of horses are susceptible, but broodmares often fall into the category of being mature horses as well as being pregnant. The specific herpes virus that is associated with the disease may often cause pregnant mares to abort. The mare herself does not even have to be infected initially, but if she is bred to a stallion that is infected then the infection will spread to the mare via the infected semen.

Other symptoms include swelling of the legs, increased respiration rates and occasionally a skin rash. There are also some viruses that are present, but undetectable unless tested for in a clinic. Laboratory examinations are often required to diagnose the disease. The mortality rate can be as high as 33% and the abortion rate in mares can reach 50%. The disease is spread through nasal discharge and through breeding.

A live modified EVA vaccine was made available in 1985 after the breakout in Kentucky. To help Quarter Horse owners, the American Quarter Horse Association is offering their service of holding vaccination records as a free courtesy to horse owners. This makes it easy for a breeding farm to call the AQHA and verify that a horse has been vaccinated.

Make sure if you have concerns or questions to contact the AQHA in regards to this vaccination.