EHV (Equine Herpesvirus) is a ‘special’ virus because it is endemic (everywhere!) Generally it causes mild respiratory symptoms, but it can turn occasionally nasty invading deeper into the neurological system (hence neurological effects). As many people have asked, vaccination does decrease the risk of EHV as it reduces the risk of viral shedding, improving herd immunity and meaning that there will be less chance of it being spread around between horses. The vaccine is truly effective for a short period of time however; if you want general cover then you can do an annual vaccination, however better protection will be provided by vaccinating every 6 months and if you are at high risk then you can do every 4 months. Pregnant mares should be vaccinated during the 5th, 7th and 9th month of pregnancy.
We advise our clients (especially those who are planning on competing, or who have breeding horses for example), to vaccinate. The primary vaccination can be given to any horse over 5 months old, and a second should be given 4-6 weeks later, followed by the booster every 4-6 months.
You can read more about the EHV outbreak earlier this year from the Animal Health Trust, along with some advice on monitoring horses that may be at risk.