There have now been 2 confirmed cases of the paralytic form of Equine Herpes Virus (EHV) infection on a yard in the Cotswolds. Another yard has been closed and is under surveillance. There have only been 4 confirmed outbreaks of the paralytic form countrywide since November last year so this manifestation of the disease is uncommon. The more usual presentation is that of respiratory disease causing coughing, nasal discharge and fever. Most horses will already have had equine herpes virus when they were youngsters and they usually become carriers of the virus. This is why racehorse trainers vaccinate their young horses against it, thus avoiding training days lost when the horses come into contact with it for the first time. When the horse is older and under stress the virus will sometimes recrudesce (become active). The horse will then show mild respiratory signs and shed the virus again, spreading it to others (similar to cold sores caused by the herpes virus in people). Incidentally, this is why yards can get virus outbreaks when there has been no horse movement on or off yard.
As already stated above the neurological/paralytic form is very rare. To put it in to context equine vets in this practice have only seen a handful of cases over many tens of years. It occurs when your horses’ antibodies to herpes and the herpes antigen bundle together and get lodged in the spinal cord. Ironically if your horse is vaccinated against herpes on a yard of unvaccinated horses showing signs then your vaccinated horse is theoretically MORE likely to develop the neurological form. Your horse is only at lower risk if the whole yard is vaccinated.
The other aspect of the virus is that if initial contact with the virus occurs during the last trimester of pregnancy then it is likely to cause abortion. Therefore mares at big studs are often vaccinated especially when there are lots of snotty youngsters about.
So in conclusion be vigilant but don’t worry too much. If your horse shows any signs of respiratory disease such as a cough or nasal discharge then avoid taking out and about until we’ve check it out. If you are worried that your horse has come into contact with any of the affected horses then monitoring your horses temperature on a daily basis is also a good idea. Any signs of respiratory disease or unexplained temperature spikes ought to be investigated.
The Horse-racing Betting Levy Board (HBLB) have produced detailed information and notes regarding EHV infection in general and can be found by following this link.