Bluetongue

BBC Scotland's rural affairs correspondent Ken Rundle explains what bluetongue could mean for a land plagued by midges, in an article first published in September 2007.

Highland cattle

The UK's first ever case of bluetongue disease has been found in cows on a farm near Ipswich in Suffolk.

The insect-borne virus, which has killed livestock across Europe, was found in a Highland cow at the Baylham House Rare Breeds Farm on Saturday 22 September.

On the Monday a second cow on the same farm was found to have a positive blood test for the disease, and an increasing number of infected animals had been identified and culled.

The occurrences were not officially classified as an outbreak until almost a week later, when other cases were confirmed at Washbrook near Ipswich, a farm in Lound and in two animals on a rare breeds farm in Baylham, near Ipswich.

Bluetongue control-and-protect zones, outlined by Defra, came into place on 29 September following the announcement that there had been 11 cases of the disease confirmed.

The zone comprises parts of Norfolk, Suffolk, Essex and Cambridgeshire.

No movements in or out of the zone are allowed. Some movement inside the zone is allowed for animals going direct to slaughter.

No surprise

Bluetongue normally affects ruminants like sheep, cows, deer, goats and camelids (camels, llamas, alpacas, guanaco and vicuńa). It was first discovered in South Africa, but in recent years has spread into northern Europe.

Ten years ago no one in Britain believed bluetongue disease posed a threat to Britain. Since August 2006, nearly 3,000 cases of the virus have been found in the Netherlands, Belgium, Luxembourg, Germany and northern France.

This spread had already fuelled fears of the disease's arrival in the UK, and the discovery of the case in Suffolk was no surprise.

Bluetongue is passed between animals by a species of biting midge (Culicoides variipennis). A midge that has bitten an animal with the virus passes it on by biting an uninfected animal.

Cold weather

Defra sign

According to the Department for Environment Food and Rural Affairs (Defra), bluetongue cannot be transmitted directly between animals, and the disease does not affect humans. Without the live midge the disease cannot spread, and as most midges die out in the cold of winter there is some hope the cycle being broken.

There are a number of different midges capable of spreading the disease including one that lives in the sheltered areas of farmyards. It is believed that this, combined with last year's mild winter, coud have led to the epidemic on the continent.

Expert opinion

Prof Jennifer Mordue of the School of Biological Sciences at the University of Aberdeen spoke about her research into midge DNA.

Professor Mordue

Working alongside Edinburgh University and the government laboratory at Pirbright, she has carried out research into how the genetics of the midge relate to bluetongue disease.

Click here to hear her interview with Ken Rundle .

Risk assessments

Live animal imports from bluetongue-infected areas must be tested, so it is thought that the wind may have blown a midge from the continent to Suffolk.

Experts have found that a midge can travel about 1.5 to 2km (1-1.2 miles) a day, and up to 200km (124 miles) if windy. The Met Office has been providing the government with regular risk assessments based on weather and wind conditions between the continent and the UK.

Animals with the disease experience discomfort, with flu-like symptoms, high temperatures and breathing problems.
Swelling and haemorrhaging in and around the mouth and nose are common, although the blue tongue, caused by haemorrhaging under the skin, is rarely seen.

Animals may become lame and have difficulty eating. Symptoms tend to be worse in sheep. Once infected, up to 70% of a flock of sheep can die from the disease.

Reduction in yield

Infected animals can recover - and become immune - but productivity is reduced with milk yields in dairy herds dropping by about 40%.

Sheep in field

Although sheep are most severely affected, cattle are the main mammalian reservoir of the virus and are very important in the epidemiology of the disease, according to Defra.

Farmers say the arrival of the disease is devastating for an industry already struggling with foot-and-mouth.

Page first published on Tuesday 25th September 2007
Page last updated on Thursday 16th October 2008

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