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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. Bluetongue has been spreading northward since October 1998, perhaps as a result of global warming,[4] which may promote viral survival and vector longevity during milder winters.[5] In August 2006, cases of bluetongue were found in the Netherlands, then Belgium, Germany, and Luxembourg.[6][7] 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. [8] Since then the virus has spread from cattle to sheep in Britain.[9] By October 2007 bluetongue had become a serious threat in Scandinavia and Switzerland.[10] Although the disease is not a threat to humans the most vulnerable common domestic ruminants in the UK are cattle, goats and, especially, sheep.
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