Bluetongue Disease - Epidemiology

Epidemiology

Bluetongue has been observed in Australia, the USA, Africa, the Middle East, Asia and Europe. Its occurrence is seasonal in the affected Mediterranean countries, subsiding when temperatures drop and hard frosts kill the adult midge vectors. which may promote viral survival and vector longevity during milder winters. A significant contribution to the northward spread of Bluetongue disease has been the ability of Culicoides obsoletus and C.pulicaris to acquire and transmit the disease, both of which are spread widely throughout Europe. This is in contrast to the original C.imicola vector which is limited to North Africa and the Mediterranean. The relatively recent novel vector has facilitated a far more rapid spread than the simple expansion of habitats North through global warming. In August 2006, cases of bluetongue were found in the Netherlands, then Belgium, Germany, and Luxembourg. In 2007, the first case of bluetongue in the Czech Republic was detected in one bull near Cheb at the Czech-German border. In September 2007, the UK reported its first ever suspected case of the disease, in a Highland cow on a rare breeds farm near Ipswich, Suffolk. Since then the virus has spread from cattle to sheep in Britain. By October 2007 bluetongue had become a serious threat in Scandinavia and Switzerland and the first outbreak in Denmark was reported. In autumn 2008, several cases were reported in the southern Swedish provinces of Småland, Halland, and Skåne, as well as in areas of the Netherlands bordering Germany, prompting veterinary authorities in Germany to intensify controls. Norway saw its first finding in February 2009, when cows at two farms in Vest-Agder in the south of Norway showed an immune response to bluetongue. Norway have since been declared free of the disease in 2011.

Although the disease is not a threat to humans the most vulnerable common domestic ruminants in the UK are cattle, goats and, especially, sheep.