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Equine Herpes Virus

EHV is a virus found in horses virtually all over the world. Once a horse is infected, the virus remains in the system and can reactivate in the future. Of the four main types, EHV-1 and EHV-4 are the most common in the UK.

  • EHV-1 which can cause signs of respiratory disease in young horses (runny nose, coughing, raised temperature), abortion in pregnant mares (usually later in pregnancy and sometimes in large outbreaks involving multiple mares) and sometimes paralysis in horses (of all ages). The virus affects young horses more than older ones. Older horses are less likely to show signs of infection, but are just as likely to spread the virus.
  • EHV-4 which usually only has a minimal effect on breathing and can occasionally cause abortion
  • EHV-3 which is a reproductive disease that causes pox-like lesions on the penis of stallions and the vulva of mares
  • EHV-5 which is associated with an unusual type of lung condition in adult horses

Symptoms of EHv-1

The virus usually hits the news when EHV-1 causes paralysis, which can range from mild uncoordination of the hindlimbs, to total paralysis where the horse is unable to stand. This can be very alarming for horse owners, can occur at any time of the year and in horses over the age of five years. When paralysis is seen, the horse will usually have been infected or reactivated the virus between one and two weeks earlier. However, whether paralysed or not, this virus affects the wellbeing of horses and if you spot a runny nose, breathing difficulties, coughing or raised temperature, be suspicious and take action – especially if horses come and go from your yard a lot and could have been in contact with other horses at events, rides or training.The virus usually hits the news when EHV-1 causes paralysis, which can range from mild uncoordination of the hindlimbs, to total paralysis where the horse is unable to stand. This can be very alarming for horse owners, can occur at any time of the year and in horses over the age of five years. When paralysis is seen, the horse will usually have been infected or reactivated the virus between one and two weeks earlier. However, whether paralysed or not, this virus affects the wellbeing of horses and if you spot a runny nose, breathing difficulties, coughing or raised temperature, be suspicious and take action – especially if horses come and go from your yard a lot and could have been in contact with other horses at events, rides or training.

How is it spread?

EHV respiratory infections are mostly spread from horse to horse through droplets from coughing and snorting. EHV droplets do not travel long distances (no greater than 50m), so reducing close contact between horses will greatly reduce risk of spread. Infected aborted fetuses and their placentas can be dangerous sources of EHV for other pregnant mares, especially if the abortion occurs within restricted stabling space. The virus can be transmitted by both people and equipment because it can survive for up to a month once it has been shed by a horse.

What do I do if I think we have EHV in our yard?

Call your vet immediately and consult the HBLB Code of Practice if you are dealing with an abortion. 

What do I do if EHV is confirmed?

Your vet will advise specifically on how to isolate affected horses and on the hygiene/cleaning procedures to be followed, but in general...

  1. If an abortion has occurred, special procedures must be followed – your vet will specify what these need to be. Isolation will need to be for at least 28 days after the last abortion, so be prepared for some crucial short term changes to yard routine.
  2. Thoroughly clean equipment, surfaces and vehicles with a steam cleaner and apply an appropriate disinfectant that destroys viruses. This should be done in between occupants. The disinfectant needs to be applied in the correct dilution to be effective.
  3. Use separate equipment and change outer clothes between unaffected and affected horses. See to affected horses last. Make sure that everyone washes their hands between horses.
  4. You need to have and follow a proper yard hygiene and disinfection policy. Please see our separate factsheet.