[Bluetongue, an emerging disease in Northern Europe]

Bluetongue is a non contagious viral disease of sheep transmitted by bites of haematophagous midges. The disease is caused by an orbivirus belonging to the Reoviridae family. The genome is segmented in 10 double-strand RNA encapsidated in a non-enveloped spherical particle with a icosaedral symetry. Twenty distinct serotypes have been identified so far, each of them inducing limited cross-protection against the others. Sheep are usually the only ones showing clinical signs like pyrexia, congestion of mucosa and cyanosis of the tongue. However, cattle, goat and wild ruminants can be asymptomatically infected. Formerly restricted to the area between the 30/40th south and 40/50th north parallels, the infection has progressively extended to the south of Europe and was more recently introduced in the north. The reason for this extension might be twice: the northward spreading of the tropical vector Culicoides imicola and the adaptation of the virus to a yet unknown endemic biting midge. Control of the disease is based on the use of live-attenuated or inactivated vaccines specific of the serotype. In free area, emergency measures can also consist in the rapid detection and elimination of the outbreaks.