You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Herpesvirus is a serious disease of horses and ponies and owners should ensure that their animals are properly vaccinated

Some horses are more susceptible to equine herpesvirus infection than others, especially :

• Horses under 2 years of age
• Pregnant mares
• Competitive horses
• Horses under stress

There are 2 main subtypes of herpesvirus that affect horses and ponies : equine herpesvirus 1 (EHV-1) and equine  herpesvirus 4 (EHV-4). 

These viruses can cause different diseases including :

• Respiratory disease (EHV-1 and EHV-4)  called equine viral rhinopneumonitis (or "Rhino" *), signs are
  • Cough
  • Discharge down the nose - clear or purulent (called the "snots")
  • Discharge from the eyes
  • High body temperature (fever) - up to 106^o F

  The respiratory disease tends to be milder with EHV-4 than with EHV-1.

• Abortion (EHV-1) - occurs 14-120 days after exposure to the virus, usually in the last trimester. The mare may show no signs of illness.
• Early death of foals (EHV-1)
• Neurological disease - weakness, ataxia (EHV-1)
• Peracute vasculitis and death (EHV-1)

EHV-2 and EHV-5 are present in most horses but rarely cause disease although they have been associated with cases of conjunctivitis and respiratory disease. 

EHV-3 rarely causes venereal disease but this is not serious and does not need treatment.

Herpesviruses can become latent and asymptomatic in horses (as they do in other species) but they can be reactivated and cause disease at any time. 

Vaccines that are available against equine herpesvirus contain inactivated virus (one or both types) and they are given by intramuscular injection. Initially two doses are given 3-6 weeks apart, and booster vaccinations are recommended every 6-12 months. Special vaccination recommendations may apply for pregnant mares and the manufacturers specific recommendations should be followed.

The frequency with which the vaccine should be given depends upon local circumstances and your veterinarian will advise on the best vaccine and protocol to use in your geographical area.

* Rhinopneumonitis due to EHV must not be confused with Rhinovirus - which is a different disease. CLICK HERE 

Updated October 2013