Everything You Need To Know About Equine Herpes

Equine herpes is a serious condition, of which there are several strains. Infected horses can quickly spread the virus to other horses, as it is highly contagious, and it is therefore important to understand what steps need to be taken if you believe any of your horses may be infected.

Once a horse has been infected, it remains infected for life, and the virus can re-emerge when the animal is stressed. 

Incubation and symptoms

Depending on the strain affecting your horse, the incubation period is typically between 4 and 10 days, but can be as short as 24 hours, after which time they will start showing symptoms.

Equine herpes causes respiratory problems, and depending on the strain, more serious symptoms may manifest.

Symptoms of equine herpes include:

  • Raised temperature
  • Nasal discharge
  • Coughing
  • Losing interest in food
  • Weakness
  • Lethargy
  • Anorexia
  • Enlarged lymph nodes
  • Strange gait

Horses may be exhausted and lean against walls for support. They may be unable to get back up if they lie down.

Different strains

EHV-1 causes respiratory problems, and can also cause abortion in pregnant mares, neurological problems, and paralysis. The standard strain of EHV-1 usually causes nothing more than a cold, however, it can infect white blood cells, and if this occurs, the virus can be carried to the uterus, causing abortions in pregnant mares, or the central nervous system, which causes the neurological form of the virus, which is can be fatal.

EHV-3 is a venereal disease, which does not affect the respiratory system. It is transmitted through skin to skin contact between horses, shared equipment, and humans who have handled an infected horse. Symptoms differ from the other strains, and if you notice blister type lesions around the genital area, or around the muzzle of a foal you should notify your veterinarian.

EHV-4 affects the respiratory system can occasionally lead to abortion in pregnant mares.


It is very important to follow proper quarantine procedures once you suspect that a horse has become infected, as not only can the virus be spread from horse to horse through direct contact, and the inhalation of respiratory secretions, but it can also spread from contact with shared tack.

Personnel must be diligent in cleaning and disinfecting to prevent the risk of infection from tack, feed and water tubs, and human to horse contact. Humans cannot be infected with equine herpes, but can spread the disease between animals through contact.

If a horse starts displaying any of the symptoms mentioned, you should isolate them and call a vet, and any other horses who have been in contact should remain in the yard to prevent the risk of it spreading further afield until the vet has confirmed a diagnosis.

Some horses may not display any symptoms, but still be infectious to other horses. Infected horses are contagious for two to three weeks, but may appear healthy. Such horses are infectious from the moment their fever spikes.

Recovery and treatment

Most horses will make a full recovery from the respiratory symptoms of equine herpes, however, the neurological form of the disease can be deadly. If a horse does not become recumbent (unable to get up after lying down) it will likely make a full recovery, however almost half of horses who do become recumbent don’t survive.

There is no cure for the disease, as it is a virus, but anti-inflammatory drugs can be used to help treat the symptoms.


Vaccinations are available, as a method of prevention. You must consult your veterinarian for recommendation based on your circumstance, as care must be taken to only carry out vaccination on healthy horses.

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