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Equine Herpes Virus (EHV)

January 2020 

EHV is contagious and can cause respiratory disease, abortion and neurological problems in horses. There are nine strains of EHV; EHV-1 and EHV-4 are the most common in the UK.

EHV-1 is less common for respiratory disease but can cause abortion and neurological disease. EHV-4 commonly causes respiratory disease.


Not all horses with EHV show the same signs and some may only show mild signs or even no signs at all. A high temperature is often the first indicator that your horse is unwell, often before they show any other signs.

If you notice your horse is showing signs of ill-health or has a high temperature it is always sensible to isolate them as a precaution and contact your vet for advice. If you’re not sure how to take your horse’s temperature, please watch our video below:

1) Respiratory

Clinical signs of EHV-1 and EHV-4 respiratory disease are very similar to equine flu and can include:

  • A high temperature
  • Nasal discharge
  • A dry cough
  • Loss of appetite
  • Reduced performance
  • Lethargy/depression 


2) Neurological

EHV-1 can cause severe disease of the nervous system that is often fatal. Affected horses may not be able to pass urine or droppings, can display signs of poor limb coordination (commonly in the hind limbs) and in severe cases are unable to stand. Outbreaks of this strain is normally rare. 

3) Abortion

Pregnant mares can suddenly and unexpectedly miscarry their unborn foal.

Further information about abortion caused by EHV-1, the measures that can be taken to prevent the disease or steps to take in the event of an outbreak can be found here

How the disease is spread

EHV is a contagious viral disease which can be spread via direct horse to horse contact (for example nose to nose), aerosol droplets over short distances by coughing and snorting and indirectly for example through contaminated equipment, handler clothing and boots.

EHV can be spread to others from contact with an infected miscarried foal or the placenta (the structure that provides oxygen and nutrients to the foal during pregnancy).

EHV lays dormant in many horses, meaning they become carriers of EHV. The carrier will often show no signs of disease. The virus can be reactivated during stressful conditions (for example during travelling or moving yards) and spread to other horses.


As the disease can spread easily and has the potential for serious consequences, the BHS strongly recommends that yards inform others if they have an outbreak so potential in-contact horses can be quickly isolated and monitored to help decrease the risk of spread. If you have any concerns for your horse contact your vet immediately.

Be vigilant if you have pregnant mares on your yard and speak to your vet for advice.

Read our advice and the simple steps you can take to prevent the spread of disease.


Vaccinating your horse can help prevent both respiratory disease and abortion caused by EHV-1 and/or EHV-4. Vaccination is especially recommended for horses under the age of five as they may be particularly susceptible to respiratory disease caused by EHV-1. Vaccination can also help reduce the amount of virus spread to others by an infected horse. Speak to your vet for advice on the EHV vaccine. 

Further information:

More information on EHV can be found on Horse Dialog.

In partnership with Professor Josh Slater, Zoetis have produced a series of videos to highlight the key facts of EHV that horse owners need to be aware of. The videos are available to watch from the following links:

More information on EHV can be found in The Horserace Betting Levy Board (HBLB) EHV Code of Practice 

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