Outbreak of Equine Herpes Virus

Outbreak of Equine Herpes Virus (2015)

Dear Horse Owner                                                                                          08 December 2015

Most of you will be aware of the outbreak of Equine Herpes Virus at Mistico Stable yard by now.

I just need to bring the following facts to your attention so everyone has a better understanding of the disease, the epidemiology and the ways in which you can protect your horse and minimize the risk of Herpes infection to your horse in the future.

In short, just a few facts about Herpes:

  1. Herpes is a viral infection which affects the respiratory system, the central nervous system and the reproductive system.  The symptoms therefore may present as a nasal discharge (cold, flu-like symptoms), neurological signs where horses become ataxic (wobbly) or even recumbent and also as a cause of abortions in late pregnancy in mares, stillbirths or weak foals.
  2. Equine Herpes Virus (EHV) comes in Types 1 – 5, with type 4 the more common type causing respiratory symptoms in younger foals and EHV type 1 causing abortions and the feared central nervous system symptoms of ataxia and recumbency.  Type 1 can also cause respiratory disease, which is its most common form, in addition to neuro and abortions. Type 4 can rarely cause neuro signs, but not in the outbreak form.
  3. Horses are often asymptomatic carriers of EHV and may shed the virus via nasal secretions for extended periods of time, especially when stressed.  Stress will commonly be due to transport, attending shows, moving horses to a new yard etc.
  4. The incubation period for EHV is 5 – 10 days.  The typical symptoms are high fever, depression, reduced appetite and in some cases neurological symptoms like ataxia, bladder paralysis and recumbency.  In pregnant mares abortions can take place.  Depending on the strain, most horses may only show a mild fever or mild upper respiratory signs, while others may go on to develop neurological symptoms.  Neurological symptoms can sometime occur up to 2 weeks after the initial illness, but can also occur without any previous symptoms.
  5. Nasal shedding of the virus can be as short as 4 days and as long as a month.  The prolonged shedding period is often seen with the neurological strain of EHV-1.
  6. Controlling the spreading of EHV includes the isolations of affected horses, good antiseptic and hygienic protocols and the use of vaccines.

Equine Herpes Virus is a common infection amongst horses and often horses become infected as foals and remain carriers for life.  The neurological strain of EHV-1 is not common but is definitely on the rise world-wide and South Africa is no exception.

The precautions that horse owners can take to minimize the risk of clinical EHV are the following:

  • Minimize stress factors as far as possible;
  • Avoid direct and indirect contact between horses at shows by not sharing tack, water buckets etc.;
  • Vaccinations:  vaccinations should be given as a primary vaccination, a month later a booster and thereafter every 6 months.  It is important to note that vaccinations will limit the shedding of virus and thereby minimize outbreaks and clinical cases but will not prevent clinical disease or the neurological syndrome of the disease.  Vaccination will however decrease the severity of clinical signs and shorten the course of disease.  Vaccination is recommended though.

If you have any questions you are free to contact me at Wellington Animal Hospital on 021-8731196 or on my cellphone 083 631 4603.


Dr Deon van Tonder