First recorded outbreak of equine viral arteritis in the United Kingdom.

Equine viral arteritis was diagnosed for the first time in the United Kingdom in 1993. The outbreak began on a non-thoroughbred stud in south Nottinghamshire and spread to five other premises through chilled semen used for artificial insemination and from acutely and subclinically infected mares returning home. The outbreak was contained on these six premises by means of voluntary movement restrictions. The most commonly observed clinical signs were typical: pyrexia with depression, and conjunctivitis with periorbital oedema; nasal discharge, and oedema of the distal limbs, prepuce and mammary glands were less common. The first mare to be covered by a recently imported stallion was the first animal to be affected. The mare was resident and no new mares had arrived on the stud during the previous five months. About 100 animals became infected during the outbreak, including three indigenous stallions. Equine arteritis virus was isolated from semen and heparinised blood samples and seroconversions were demonstrated by using the equine arteritis virus neutralisation test. Although the outbreak was contained, the free movement of animals within the European Union increases the possibility of infected stallions being introduced into the UK.