Many horse owners don’t know that there are at least four types of Equine Herpesvirus. The ones that we associate the most are EHV-1 and EHV-4. EHV-1 is the most prevalent and often the most destructive to the horse. EHV-1 causes severe respiratory problems, abortion in mares and neurological disease. EHV-4 causes upper respiratory infection only. Most horses, however, contract EHV-1 and is it usually first diagnosed by runny noses, fevers, coughs and broodmares that are aborting.