A study performed at Cornell University examined 176 equine herpes virus 1 (EHV-1) isolates, which had been collected from horses for the past 23 years. They wanted to determine how many of them contained the recently identified genetic change believed to cause neurological disease.
Of the 176 samples, 19 had the mutation, and 16 of those had neurological involvement. They also determined that horses infected with that particular type of EHV-1 were 162 times more likely to develop neurological signs, but 24% of the 21 cases of neurological involvement were horses infected with the more common, garden-variety strain of the virus.
Bottom Line: This study confirms that while one strain of this virus is more likely to produce neurological signs, even the more common strain may sporadically result in neurological disease. It also drives home the message that while we must be quick in identifying an outbreak involving the strain at high-risk of neurological disease, finding herpes virus is not a cause for panic. Most horses harbor this virus and carry it for life. In this study, only 3.2% of the horses infected with the common strain developed neurological signs.