13/01/2020
******* Equine Herpes Virus *******
Equine Herpes Virus is a very infectious virus which can cause respiratory disease, neurological disease and abortion in mares. If you have any questions regarding EHV, please don’t hesitate to get in touch. If you are concerned about your horse, particularly if he or she has a high temperature, please give us a call straight away. Biosecurity measures are in place.
Risk of infection can be minimised with good biosecurity measures, i.e avoiding close contact or sharing of water or feed buckets with other horses, particularly at competitions, and isolating new horses at livery yards. Known cases should be isolated
Should we be worried about our own horses, and what can we do to protect them from infection? Hopefully we can answer your questions in the information below.
There are actually five forms of Equine Herpes Virus (EHV). As vets, we most frequently deal with EHV-1 and EHV-4. These strains of EHV are very common, and almost every horse will have been exposed or infected at one time or another. The most common signs are those of an upper respiratory tract infection. Depending on the infecting strain and the individual horse’s immune response, the severity can vary markedly from little or no clinical signs to a high temperature, lethargy, purulent nasal discharge and cough. The incubation period ranges from approximately 2-10 days. EHV can set up a latent infection, ie the virus remains in the horse after cessation of clinical signs, and can become reactivated at times of stress. The horse might not exhibit clinical signs during these periods but can spread EHV in oral and respiratory secretions.
In pregnant mares, EHV-1 and EHV-4 can also cause abortion. The abortion tends to occur in late pregnancy regardless of the time at which the mare became infected. If many mares on a stud are infected, particularly with EHV-1, we might therefore see ‘abortion storms’ in which many mares abort within a short period of time. Clearly, the emotional and economic effects of this can be terrible.
In rare cases, EHV can invade the nerve tissue of the spinal cord. The resulting inflammation causes weakness and ataxia (wobbliness) and can quickly progress to recumbency. Unfortunately, the majority of these neurological cases are fatal.
As EHV is a virus, we cannot kill it with antibiotics. Treatment involves supportive therapies such as anti-inflammatories, and administration of intravenous or oral fluids.
Since EHV is so widespread within the horse population, it is very difficult to pin point the source of infection.. There is a vaccine for EHV-1 and EHV-4, which can reduce the severity of clinical signs and reduce the shedding of the virus by infected horses, but does not give complete protection from infection. It is currently not known whether the vaccine is effective against the neurological form of the disease. ‘Zylexis’, which is an immune stimulant, can also be used to help reduce the severity of respiratory signs, but is not known to have any effect on the neurological form of EHV.
We have produced a small poster providing information regarding EHV and sensible biosecurity precautions. If you would like one to pin up at your yard please let us know and we'll be happy to e-mail it to you. If you have any questions not covered by the poster please don't hesitate to contact us.
