Equine viral arteritis (EVA) is a contagious disease causing abortion in pregnant mares. It is a notifiable disease – there is a legal requirement to notify DEFRA in the event of positive tests for EVA. The severity and variety of symptoms caused by EVA can vary widely. Infection may be obvious, or there may be no clinical signs at all. The clinical signs of EVA include flu-like respiratory disease and fever. Mares infected late in gestation may give birth to foals with potentially fatal breathing problems.
The equine arteritis virus causing EVA is most frequently spread through direct contact, with infected horses transmitting the virus through respiratory secretions. However, it is also spread through the semen of infected stallions, either directly during mating or indirectly via artificial insemination (AI). The stallion is a very important source of the virus as, once infected, some stallions can become carriers, shedding the virus for anything from several weeks to a lifetime.
It is important to ensure that any stallions being used for breeding purposes, either directly or via AI, comply with the Horserace Betting Levy Board Code of Practice on EVA. If you are a mare owner, you shouldn’t hesitate to ask to see papers certifying that the stallion is clear and has been vaccinated, before it is allowed to breed with your mare.