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EHV refers to Equine Herpes Virus and it is a family of viruses named by numbers that commonly infects horses worldwide. In fact, the great majority of horses are exposed to EHV-1 early in life and develop a latent infection, meaning they carry the virus their whole lives without showing signs of illness. The virus seems to be “reactivated” from its dormant status under periods of stress such as travel and competition. Nine different equine herpes viruses have been identified and numbered, but the focus is on EHV-1 and EHV- 4 because those are the two that can result in serious disease in the horse.
Diagnosis of equine herpesvirus is relatively straightforward and is based on clinical signs along with virus identification from either a nasal swab or a blood sample. Alternatively, two blood samples taken 2-3 weeks apart can also be used to diagnose an EHV infection based on a significant increase in antibody titer. Because it is important to know what a horse, herd, or barn is infected with in order to provide appropriate, early treatment as well as to limit an outbreak, it is recommended to contact a veterinarian for physical examination and diagnostic testing upon discovering any FUO (fever of unknown origin), respiratory signs, or neurological signs. The vet can also provide guidance on isolating sick horses and implementing other biosecurity protocols on the farm.
Preventing an outbreak of the respiratory, neurologic, or reproductive forms of equine herpesvirus relies on a two-pronged approach that is developed with the farm veterinarian: 1) appropriate vaccination and 2) common-sense biosecurity.