Equine Herpes Virus: Just the Facts

By Kenneth L. Marcella, DVM

Rhinopneumonitis or “Rhino” is a disease caused by Equine Herpes Virus (EHV) and it has figured prominently in the news this spring. Numerous serious outbreaks were recorded at racetracks and training facilities resulting in quarantines and, tragically, in the deaths of some horses.

There are actually five strains of Equine Herpes Virus but it is EHV-1 and EHV-4 that cause the most trouble. EHV-4 is the respiratory agent causing high fevers, clear to thick nasal discharge, increased lung sounds, mild coughing, depression and loss of appetite. This strain is also known to cause abortions and neurological problems. EHV-1 is the reproductive agent causing primarily abortions but it can also cause respiratory problems and neurological disease. Further confusing is the fact that horses with either EHV-1 or 4 can look alike clinically.

Rhino infections are spread from horse to horse, slowly, through close contact with secretions. Once infected, EHV can live in nerves and lymph tissue for the life of the horse and situations of stress will cause it to reoccur. Vaccine protection is available and owners should discuss their horses’ needs with their veterinarian.

Dr. Ken Marcella is an equine veterinarian at Chattahoochee Equine in Canton, GA.