Equine Herpes Virus (EHV-1) 2021


EHV causes four clinical syndromes:

  1. Respiratory
  2. Abortion
  3. Neonatal foal death
  4. Neurological disease – the paralytic form, which may or may not be related to previous or on-going respiratory disease

Respiratory Disease: What to look out for

  • Fever
  • Coughing
  • Nasal Discharge

Neurological Disease: What to look out for

  • Incoordination of the hind (and occasionally fore) limbs
  • Urine retention/dribbling  – can present as mild colic
  • Bladder weakness
  • Recumbency (inability to rise)
  • Neurological signs may be preceded by fever and respiratory signs



The virus is a respiratory infection. Spread occurs from horse-to-horse contact (nose-to-nose) and any nasal discharge will be contagious. People can also transmit the virus by handling an infected horse and then touching another unaffected horse; likewise tack and equipment can spread the virus from horse to horse. The virus can also spread in the air (aerosol spread), especially to adjacent stables. The virus cannot spread large distances in the air and does not survive for long periods in the external environment. Close contact between horses within a yard or between adjacent yards is usually required to allow spread.

The incubation period may be as short as 24hours, but more typically is approximately 4 – 6 days, and horses are most infectious in the early stages of infection (when the temperature is raised).

Another important feature of the Herpes viruses is their ability to lie dormant (latent) in the body. A horse can therefore be infected for life, and can intermittently discharge the virus from the nose and infect susceptible horses. Stress may result in a latently infected horse starting to shed virus into the environment again, so avoid stressful stimuli in your yard.



  • Call BELL EQUINE on 01622 813700, if disease is suspected
  • Isolate any horses showing a temperature rise and/or respiratory signs
  • Keep pregnant mares away from other horses, especially new arrivals.
  • Minimise stress, where possible, e.g. by avoiding prolonged transport. So keep your horses as comfortable as possible in a normal routine.
  • Isolate any new horses coming onto a yard for at least 10 days
  • Be fastidious with hygiene at all times, such as avoid nose to nose contact between visiting horses, disinfect horseboxes between transporting different horses and change clothing and wash hands after contact with other horses
  • See British Equestrian guidelines for management of showjumpers returning to UK from high risk areas of Europe.
  • See FEI for further information and international updates about EHV-1.
  • In a futher step to minimise spread, British Equestrian also recommends the implemenation of a new self-certification process for riders to declare that their horses are healthy have not been in contact with any others showing signs of infectious disease. Competitors should follow the information on each competition schedule on how to submit their information. This process will be in place for 29 March to 12 April but could stay in place should the risk level dictate.


This is NOT recommended in the face of an outbreak. Vaccines against Equine Herpes viruses are available, but they have never been shown to be effective against the neurological form of the virus. The vaccine is not 100% effective and will not necessarily prevent a horse from becoming infected by the virus.

Vaccination has a role, when combined with good biosecurity and hygiene measures. If you horse is healthy and is not linked to any outbreak, then there is no reason not to vaccinate as that way you will be doing all you can to prevent EHV.

The vaccine has to be given as 2 doses 4-6 weeks apart, followed by 6 monthly boosters.  And if it is administered it is advised to vaccinate the whole yard to reduce the risk of infection becoming established in the overall population. Pregnant mares can be vaccinated at 5, 7 and 9 months of gestation to prevent EHV-1 abortion.

We recommend that broodmares should recieve their EHV vaccinations every year. Racehorse travelling abroad to other countries may require EHV vaccinations depending on jurisdictions (e.g. for racing in France.)

Other horses which travel away for competitions particualrty when this involves overnight stays in shared stabling may benefit from group EHV vaccinations. Please discuss this with our vet team before making plans.

Please call BELL EQUINE on 01622 813700 if you have any questions and look out for further updates here or on our Facebook page.

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