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Last Updated: Saturday, 29 September 2007, 11:19 GMT 12:19 UK
'Dancing' disease set for long run
by Matt McGrath
BBC World Service environment reporter

The virus is transmitted by midges
Computer model of the bluetongue virus protein
As a protection zone is set up in Suffolk following government confirmation bluetongue is circulating in the UK, Dutch veterinary experts explain the dangers of the disease:

For scientists with experience of bluetongue virus, it's always FFF - fever, face and feet.

The virus infects the mucous membranes in cattle and sheep and other ruminants causing facial swelling and high temperatures.

And according to Dr Piet Van Rijn of CIDC Lelystad, the Dutch national reference lab for exotic disease, swelling in the limbs exerts such pain in cattle they dance on their feet.

Warning

The Netherlands has plenty of experience in dealing with bluetongue.

Dr Armin Elbers is an epidemiologist, from Wageningen University. In 2003 he warned the Dutch government that bluetongue would spread from the south of Europe to northern countries because the midges that carried the disease were likely to migrate northwards as the climate changed.

We still don't know where it came from
Dr Armin Elbers
Disease expert, Wageningen University

But when the first cases were diagnosed in the Netherlands in 2006, the scientists were surprised. The version of bluetongue found in Dutch cattle and sheep was not the same as the one found in southern Europe.

Dr Elbers explains: "The type of virus that we found in the Netherlands is called BTV serotype 8. It's different from the ones found in the southern part of Europe.

"BTV virus serotype 8 is found in Africa, South East Asia and the Dominican Republic - it came here unexpectedly from somewhere else. We still don't know where it came from."

Horse manure link

The virus was first discovered at a rare breeds farm in Suffolk
Vaccination is the only way to prevent the disease

Experts say the outbreak that began in the Netherlands, Belgium and parts of Germany and France in August 2006 might have been caused by horses, or more specifically their manure.

The theory is that horses from many different parts of the world came to a European show jumping event in the summer of 2006 and the midges that spread the virus came with them, travelling in horse manure.

This, say the scientists, might explain why the northern European outbreak was of the same serotype as found in other parts of the world such as Asia and South America.

Animal movement blamed

Dr Elbers believes that both natural and commercial factors have helped spread the disease.

He said: "We've looked at the wind spread in this epidemic and we think that wind might be a possibility for spreading the disease within Europe. Another aspect is the transportation of animals, particularly in Belgium.

"Animals are born in the eastern part of the country but fattened in the western part so the disease has been spread much more quickly because of the transportation of infected animals."

The disease is very difficult to deal with. It may not be as deadly to animals as foot and mouth or BSE but it is extremely difficult to get rid of.

Dr Elbers explains: "It is very different in cattle than it is in sheep - In cattle farms you only see a few sick animals but 50 to 60% can be infected meaning there is a large reservoir to spread the disease.

"Preventing contact between the midges and cattle is very difficult - the only way to prevent clinical disease is vaccination but it will be a trade-off because it is expensive."

Fears

Other diseases are also spread by midges such as West Nile virus and Rift Valley fever - with climate change it could come to these northern European regions and be a problem not just for agriculture but for human health as well
Dr Piet Van Rijn, CIDC Lelystad, Dutch disease centre

Climate change has been blamed for the spread of the midges that cause the disease - but Armin Elbers says its effects are indirect.

He said: "The midges have been here for hundreds of years but because of the warmer summers there are more opportunities for the virus to replicate in these insects at a higher level and therefore the insects are more likely to pass it on to sheep and cattle.

"We are very anxious to see what happens in the coming months. The midges die away in the winter, but the key thing is whether the virus is over wintering in animals.

"It can fade out but it can become endemic as in Italy where the disease is endemically infected and they have to live with the disease."

Dr Piet Van Rijn says that the real concern is the possible spread of other, more deadly infections.

He points to the examples of Rift Valley fever and West Nile virus, spread by mosquitoes which are a similar vector to the midges that spread bluetongue.

"With climate change it could come to these northern European regions and be a problem not just for agriculture but for human health as well," said Dr Piet Van Rijn.

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