The equine herpes virus plagues our horses in at least four varieties. The disease with which most horsemen on the track are familiar is rhinopneumonitis. This is caused by the herpes virus, a variant of EHV1 which causes abortion in mares. The variant has been recently named EHV4. Rhinopneumonitis caused much time lost at the racetrack.
Horses come down with a fever and a snotty nose.
They become listless and loose their appetites. With rest, they usually get back to previous form in a couple of weeks. This still represents a lot of lost time, and when a trainer keeps pushing the horse during this time, lasting damage can occur which is even more costly. Another form of the virus causes a paralytic form of rhinopneumonitis. Horses seldom recover from the effects of this form.