VETS in Belgium and Holland have reported that large numbers of the midges which carry bluetongue disease have become active in the past few days.
Farmers have been warned to watch for symptoms, and urged to vaccinate stock.
The midge is adapting to north European weather, and the World Animal Health Organisation says it could now spread over most of the European continent.
However, Ireland has remained free of the disease.
In Britain, vets and farmers have started vaccinating sheep and cattle against bluetongue.
Midges — which live for 10 to 14 days — can fly up to 2km a day, but can travel passively on the wind up to 200km.
They are believed to have recently carried a new strain of the disease to the northern shores of Australia, on monsoonal winds. This is the ninth different bluetongue serotype to be isolated in northern Australia cattle to date.
In 2006, a new strain, serotype 8, began to circulate in northern Europe, appearing for the first time in Britain last year.
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