Scientists say a livestock virus sweeping through British sheep flocks and cattle herds has now infected wild deer.

The disease, which is spread by insects, causes birth defects in lambs and can reduce milk yields in cattle.

Outbreaks have been reported in farm animals in Belgium, France, Germany, Italy, Luxembourg, The Netherlands, Spain and the UK.

European scientists say wild deer can catch the virus, and are calling for the impact on wildlife to be monitored.

Dr Mutien-Marie Garigliany, a veterinary expert at the Universite de Liege is one of a team of experts studying cases of Schmallenberg virus (SBV) in wildlife in the south of Belgium.  "It is just impossible to control midges across an area the size of Europe.”

Dr Garigliany said wild animals such as roe and red deer can potentially act as a reservoir of infection.

"We should implement specific surveillance of wild animals for SBV," he told BBC News.

He said wild boar as well as wild deer show signs of SBV infection, although it is not thought to make them sick.

SBV first appeared in south east England more than a year ago, but has now spread to every county in England and Wales.