page_title: Bluetongue disease
section_title: Epidemiology
hierarchical_section_title: Bluetongue disease / Epidemiology
caption_attribution_description: English: The molecular epidemiology of bluetongue virus (BTV) since 1998: routes of introduction of different serotypes and individual virus strains. *Presence of BTV-specific neutralizing antibodies in animals in Bulgaria, but the presence of BTV serotype 8 cannot yet be confirmed.
context_page_description: Bluetongue disease is a noncontagious, insect-borne, viral disease of ruminants, mainly sheep and less frequently cattle, yaks, goats, buffalo, deer, dromedaries, and antelope. It is caused by Bluetongue virus. The virus is transmitted by the midges Culicoides imicola, Culicoides variipennis, and other culicoids.
context_section_description: Bluetongue has been observed in Australia, the US, Africa, the Middle East, Asia, and Europe. An outline of the transmission cycle of BTV is illustrated in article Parasitic flies of domestic animals.
  Its occurrence is seasonal in the affected Mediterranean countries, subsiding when temperatures drop and hard frosts kill the adult midge vectors. 
  Viral survival and vector longevity is seen during milder winters. 
  A significant contribution to the northward spread of bluetongue disease has been the ability of C. obsoletus and C.pulicaris to acquire and transmit the pathogen, 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 had 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.
caption: The molecular epidemiology of Bluetongue virus in Europe since 1998: routes of introduction of different serotypes and individual virus strains