Science Media Centre Fact Sheet. Blue tongue disease. What is bluetongue? •
Bluetongue is a viral disease affecting all ruminants, including sheep, cattle,.
Science Media Centre Fact Sheet
Blue tongue disease What is bluetongue? Bluetongue is a viral disease affecting all ruminants, including sheep, cattle, deer and goats. Although sheep are the most severely affected, cattle are the main harbour for the virus, although goats and cattle rarely show any symptoms. The disease does not affect humans. The disease primarily affects blood vessels in the mouth, lips, nose and eyelids, leading to reddening and swelling. Symptoms vary between species, but it is generally characterised by a high fever (which may last for several days), excessive salivation, nasal discharges, swelling of the head and neck and sometimes discolouration of the tongue. The disease commonly leads to lameness, muscle degeneration and death in around 70% of cases. Animals that survive suffer long-term defects, including sterility and reduced meat production. How is the virus transmitted? The bluetongue virus is transmitted by a small number of species of biting midges of the genus Culicoides. When a midge bites an infected animal the virus passes to the midge in the blood. The virus is then passed on when the midge bites an uninfected animal. The virus cannot be naturally transmitted directly between animals. However, Defra does not rule out the possibility that the virus could be transmitted within or between flocks by unhygienic practices, such as the use of contaminated needles or surgical equipment. History and spread of the disease Bluetongue was first described in South Africa, but has since been detected in most tropical and sub-tropical countries. Since 1999 there have been widespread outbreaks of bluetongue throughout Europe, including Greece, Italy, Corsica, the Balearic Islands and some Baltic states. These cases have been beyond the virus’s normal distribution, suggesting that it is spreading throughout Europe. The disease has never previously been recorded in the UK. Defra estimates that the midge can travel between 1.5-2 km a day, although distances can be much further if conditions are suitable. How is the disease detected and treated? Although it is detectable through its symptoms (see above), according to international guidelines bluetongue is only confirmed once there is evidence that the virus is circulating between animals and vectors (carrying midges) within an area.
There is no treatment for bluetongue. Prevention may be possible by vaccination and by controlling midge populations (with insecticides or by controlling breeding sites), but neither method carries any guarantee of success. As the disease is carried by a midge vector, infected animals are not generally culled.
Sources/further information Institute for Animal Health: http://www.iah.bbsrc.ac.uk/bluetongue/BTV.htm Defra: www.defra.gov.uk/animalh/diseases/notifiable/bluetongue/about/index.htm ................................................... This is a fact sheet issued by the Science Media Centre to provide background information on science topics relevant to breaking news stories. This is not intended as the 'last word' on a subject, but rather a summary of the basics and a pointer towards sources of more detailed information. These can be read as supplements to our ‘round-up’ press releases. For more information about our fact sheets, please contact Robin Bisson at the Science Media Centre on 020 7611 8345 or email
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