Lelystad virus and the porcine epidemic abortion and respiratory syndrome.

Lelystad virus is the causal agent of a relatively new pig disease, variously known as mystery swine disease, porcine epidemic abortion and respiratory syndrome and porcine reproductive and respiratory syndrome. The virus is a small, enveloped RNA virus, that tentatively can be included in a new virus family, the Arteriviridae. The virus has infected pigs throughout the world and seems to persist in many pig populations and in individual pigs. Clinical signs of an infection with Lelystad virus are characterized by late term abortions and still birth in sows, and respiratory disease in piglets.