The vaccine against equine viral arteritis (EVA) is called Artevac. The reason we in this country are keen to vaccinate stallions against EVA is that it is actually a respiratory virus primarily that can affect mares, geldings and stallions. The respiratory infection causes 'flu-like symptoms in all horses. If a pregnant mare contracts EVA she will abort and if a farm had several mares in foal probably all would abort. Mares and geldings will get over the infection within a month usually, as will a stallion. The difference is that once a stallion is exposed to and contracts EVA he can harbour the infection in his reproductive tract possibly for life. If he then goes on to cover mares or have his semen collected for AI the virus stays in the semen even when frozen, the mare that is served then becomes infected. She then shows the respiratory signs and will spread the infection to any horses around her - other stallions or mares in foal, hence causing abortion.
Once a stallion is a shedder of EVA in his semen there is no treatment - some stallions can eventually stop shedding but you cannot count on this happening. A stallion with EVA in the UK is a notifiable situation - DEFRA will order the stallion to be castrated or exported and will certainly put a ban on his semen being used on mares. When we import semen from the continent we cannot inseminate the mare until we have received original ministry documents from the country of origin's state vets detailing that the stallion is free of EVA.
If a stallion does become EVA positive his value as a breeding stallion is severely reduced. If you were buying a new stallion and asked us for advice I would suggest that a blood sample is taken to test for EVA before any money changed hands - we test all stallions at pre-purchase exams.
Prior to vaccination we test the stallion to see if he has EVA antibodies in his bloodstream. If he is clear we vaccinate and take another sample the day of vaccination - we then carefully record in his passport that a blood test was done prior to and on the day of vaccination - we record the lab where the test was done (has to be a ministry lab). We issue an official ministry certificate that you file carefully and we enter in his passport that he is vaccinated. This really is important as we need to be able to prove that on the day he was vaccinated he was free of EVA. The course for the vaccine is a booster in approximately 6 weeks and then a vaccine every 6 months - which must be kept up once started.