Equine Herpes Virus – Neurological form
Following the outbreak of the neurological form of Equine Herpes virus in the Cotswolds in 2013 we had a large number of requests for information regarding EHV1 infection.
What causes it?
Equine Herpes Virus type one (EHV1) is a common viral pathogen found very widely in the horse population in the UK. Most horses will be exposed to this virus during their lives and frequently it goes unnoticed. Only a very small percentage of affected horses are affected by the neurological form of the disease.
Commonly EHV1 causes mild respiratory signs, coughs, nasal discharge, lethargy, occasionally high temperatures and loss of performance. In most cases rest is sufficient to bring about a full recovery and no specific treatment is required although antibiotics are sometimes used to treat secondary infections.
In some outbreaks a small number of horses develop neurological signs. This can vary from very mild to more severe with for example ataxia of the hind limbs (very much like a ‘wobbler’) and infrequently to paralysis and collapse. In some instances euthanasia on humane grounds is necessary. Mild or moderately affected horses will in many cases recover. The epidemiology is not fully understood but it is likely that the EHV1 strain causing neurological signs is slightly different from more common strains of the virus.
What should I do in case of an outbreak?
Firstly don’t panic. The incidence of horses developing serious neurological signs (even during neurological EHV1 outbreaks) is always very low. Most reported outbreaks seem limited to a hand full of horses. The virus is air borne and spreads via droplets when affected animals cough but it is easily destroyed outside the body so it does not persist long in the environment. Affected horses and horses which have had direct contact with them should be strictly quarantined. You should be extra vigilant in checking your horse daily. Its temperature should be between 36.5 and 38.5 C. If it is running a temperature above this, has a soft cough or nasal discharge call your vet immediately.
Should I vaccinate my horse?
This is controversial. Vaccines against EHV1,4 are available and widely used (especially in competition horses) but they do not protect against the neurological strain of EHV1. Thus vaccination of individual horses is unlikely to be helpful. Mass vaccination of large groups will serve to reduce the overall circulation of virus in the population and may help reduce the incidence of cases but it must be emphasised that the current vaccines are not designed to protect against the neurological form of EHV 1.