A virus that is migrating northwards

Catarrhal fever, more commonly known as bluetongue, is a viral disease found in ruminants. Although all types of ruminants are at risk of infection, among domestic varieties it is sheep that are affected most severely. The disease is transmitted by the bites of a midge of the Culicoides family and in most cases it proves fatal. It used to be frequent only in tropical and sub-tropical regions, but in 1998 cases were reported throughout the Mediterranean Basin, subsequently gradually moving northwards through Greece, Albania and Bulgaria. In the summer of 2006 the first cases were reported in Belgium. With outbreaks in the Netherlands and West Germany, never before has the disease been recorded so far north.

Previously unknown in our northern latitudes, bluetongue was described as an emerging disease by the World Organisation for Animal Health. In addition to health measures in the field, such as screening and restrictions on the transport of animals, active monitoring tools are proving very useful in tracking and understanding the spread of the virus. Although linked directly to the movement of infected animals, it seems that wind also plays a part in spreading this disease, transporting the tiny midge across potentially long distances. Satellite imagery data have made it possible to develop software that estimates the probability of the presence of Culicoides and that defines the dynamic of the spread of the various species. Bluetongue disease poses economic as well as health risks, it is crucial to develop this kind of applications to permit a coordinated management of crisis situations and a precise analysis of the contamination risk factors.