Bluetongue disease: meteorological aspects for its potential spread from continental Europe to the UK this year
Last year bluetongue came to northern Europe for the first time. The first outbreak was identified and confirmed in the Netherlands, and further cases were then detected in Belgium, France, Germany and Luxembourg. Over 2000 cases were recorded in cattle and sheep. Mortalities in sheep and cattle exhibiting signs of disease were approximately 30% and 10%, respectively.
Bluetongue is spread by biting midges. Very recent evidence from Germany indicates that some infected midges have survived the winter and have spread the disease to cattle in Germany. In the Veterinary Record paper, John Gloster and colleagues describe the meteorological conditions in the infected area last summer. One factor was the unusually high temperatures in northern Europe at that time, which would have helped the bluetongue virus to grow in the midges. The authors then discuss the conditions that would be necessary to carry midges to the UK. Midge numbers are expected increase markedly in May, as temperatures rise.
“There is evidence from outbreaks of bluetongue in southern Europe in recent years that infected midges have spread from North Africa on the wind. So, there is a real possibility that midges in northern Europe could be blown across the sea to south-eastern parts of England.” said John Gloster.
Meteorological analysis of the northern European outbreak of last year showed that the temperatures were ideal for rapid multiplication of the virus in the midges, and the winds were present to transport infected midges to the farms both within and beyond the main disease centre. Once infected, these new cases subsequently acted as new points from which the disease spread further.
The distances from our near European neighbours to the eastern counties of England are well within the travelling distance of the midges. Studies of outbreaks in Portugal, Cyprus and Turkey in previous decades have indicated that the midges had been carried 100 to 300 km by the wind from the sources of the disease further south.
Using a weather model and knowledge of the optimum conditions for the wind-borne spread of the midges, Gloster and colleagues have estimated that, if the disease does flare up again near coastal areas of Belgium, then Kent, Essex and East Anglia are likely to be at risk between four and seven times per month from May to October. There are hundreds of thousands of sheep, and tens of thousands of cattle, in these counties, providing a plentiful target for any midges that are blown in from the east.
J. Gloster1, P. S. Mellor2, L. Burgin1, C. Sanders2 and S. Carpenter2
1 Met Office, Fitzroy
Road, Exeter EX1 3PB
2 Institute for Animal Health, Pirbright Laboratory, Ash Road,
Pirbright, Woking, Surrey GU24 0NF
Veterinary Record., March 31st, 2007; volume 160, pages 422 - 426.
Further information on bluetongue can be obtained at this website, with links to other providers of information. Start at bluetongue news/
In addition to the links that are immediately on-screen you can get more links by scrolling down the page e.g.
a description of the disease diease facts > bluetongue
pictures of clinical signs in sheep, BT_clinical.pdf
and IAH media releases, with supporting information, at the start of the outbreak in northern Europe last year, BT%2028aug06.htm