Bluetongue disease: potential spread from continental Europe to the UK

UK The possibility that bluetongue disease could come to the UK on the wind from neighbouring countries in continental Europe is the subject of a paper just published in the Veterinary Record "Will bluetongue come on the wind to the United Kingdom in 2007?"

6 April 2007

3 minute read

Europe

John Gloster of the Met Office is currently working at the Institute for Animal Health’s Pirbright Laboratory, alongside the IAH’s virologists and entomologists.

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. vMeteorological 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.