Bluetongue disease—Global overview and future risks

Abstract

Bluetongue disease (BT) has spread after the first reported outbreak more than 100 years ago to nearly all the tropical and temperate regions worldwide in a geographic band between the latitudes 40°N and 35°S. Bluetongue virus (BT) is transmitted by biting midges of the genus Culicoides to susceptible ruminants like sheep, cattle, goats, and wild ruminants. Probably due to the global warming the dispersal area of the transmitting Culicoides species and by this of the BTV expanded to northern regions up to the latitude 50°N. Independent of expansion of the insect vectors BTV serotype 8 was introduced into Central Europe in 2006. The source of the BTV 8 introduction is still unknown. In Central Europe the virus found a new insect vector, midges of the Culicoides obsoletus group, indigenous in Central and Northern Europe and highly adapted to ruminants, overwintering in the stables. In summer and autumn 2006 and in the following years BT spread from the tri-border region between Germany, the Netherlands and Belgium to all neighbouring countries up to Scandinavia and United Kingdom. In the naive and genetically highly susceptible European sheep and cattle population the disease killed more than 1.5 million sheep. Trade restrictions and secondary diseases increased the economic losses. The spread could be stopped by a mandatory vaccination campaign using inactivated serotype specific vaccines. By this Central Europe could be sanitated from BT.