What is Equine Herpes?

What is Equine Herpes?

Health & Safety

Anyone who owns a horse knows that at some time or another their precious steeds will need to see a vet. It could be to get their flu and tetanus shots up to date or it could be as a result of them injuring themselves – something horses tend to be good at doing. However, there are other conditions which may arise and which need veterinary attention – one of which is equine herpes. But what exactly is this disease?

Understanding Equine Herpes

There are two strains of the virus with the first one being EHV1 and the second being EHV4. Both of the viruses affect horses in slightly different ways. The former may cause respiratory problems but it can also cause pregnant mares to abort their foals. In very rare cases, EHV1 may be the cause of neurological problems which can lead to paralysis.

When it comes to EHV4, this second strain of the equine herpes virus is more commonly the cause of respiratory problems. It can also cause mares to abort their foals but it is rarer than when a horse has contracted EHV1 for this to happen.

What Are the Signs To Look Out For?

If you think your horse may have come into contact with a horse with the disease – and all it takes is for them to nose each other for the virus to be transmitted, the symptoms you need to look out for are quite distinct and are listed below:

  • Your horse will have a high temperature
  • They will cough
  • You will see a nasal discharge
  • Your horse will be off their food – even their favourite treats

Should You Be Worried About it?

When it comes to what sort of threat equine herpes may pose to your horses' health, the answer is that you do need to first recognise there is a problem and then secondly you should isolate your horse and seek advice from your vet. Horses with the condition should not even touch noses with another horse and you should wash your hands each time you groom or touch them. Any trailers or lorries a horse has been in, needs to be disinfected afterwards as well – your vet should be able to advise which disinfectants are the most effective to use.

If you think your infected horse may have come into contact with any other horses on a yard, then these horses must remain on the yard until your vet has seen your horse and confirmed that it is in fact equine herpes. The vet will then take the necessary steps to treat all horses that may be infected with the virus.

Horses can carry the equine herpes virus and some may never show any signs of having the condition. Some people think most older horses do in fact, carry the virus having been exposed to it at some point in their lives. However, if you are concerned, then a simple blood test will reveal if a horse has been exposed or not – with one problem being the test cannot differentiate if the antibodies are actually caused by the herpes virus or by a vaccination a horse may have be given.

The Pros and Cons of Vaccinating Your Horse

There is a combined vaccine that covers both strains of the virus and there are others which work specifically on each strain. However, the combined vaccine also covers the equine flu virus. All vaccines do work effectively on the respiratory effects of both strains on horses, but they are not effective against the paralytic form of the virus.

Most vets and the Animal Health Trust advice horse owners to only vaccinate a healthy horse. Should there be an ongoing outbreak of the virus, then no horses should be vaccinated as this would reduce the risk of horses that are incubating the disease from being given the vaccine. Should a horse that is incubating the virus be given the vaccine, it could make matters worse resulting in the horse suffering a much more severe bout of equine herpes whichever strain it happens to be.

If you are considering having your horse vaccinated but notice they are suffering from some sort of respiratory disease, then you would need to get the “all clear” from your vet before they would administer the vaccine. This would mean your horse undergoing a thorough and in-depth examination by your vet.

However, if your horse has suffered from either of the equine viruses in the past and has recovered from the disease, they can be safely given the vaccine – so long as they have fully recovered and are not showing any signs of a respiratory problem. Your vet would want to make certain a horse is not at the incubation stage of the virus too. There is a downside because the vaccine is not as effective when administered to a carrier horse.

What Vets Advise

Vets and the Animal Health Trust encourage horse owners to start a routine vaccination program on their horses when they are young. This is the best way to ensure your horse does not contract the virus and the only really effective way of preventing the spread of the infection from horse to horse.

What About New Horses Arriving on a Yard?

Any new horses arriving on a yard, whether a private or livery yard should be kept away from other horses. This means stabling them away from other animals and having a turnout paddock that is away from other horses. In brief, new animals need to be kept in quarantine to ensure they are not incubating the disease. It's the best measure to set in place to avoid equine herpes from being transmitted to any other horses already on a yard.


At the end of the day good horse husbandry comes into play. New horses need to be quarantined when they first arrive on a yard not only to ensure they are not infected with equine herpes but any other conditions too. Yards, stables and paddocks need to be well maintained. Keeping water buckets, feed bowls and haynets clean is essential. Each horse on a yard should have their own equipment so that diseases and viruses are not spread by accident from horse to horse. If you have any doubts or worries about your horse having equine herpes, you need to talk to your vet as soon as possible whilst at the same time isolating them from any other horses.



Pets for studWanted pets

Accessories & services

Knowledge hub


Support & safety portal
Pets for saleAll Pets for sale