The Schmallenberg virus (SBV) has now hit 58 farms across the UK, latest figures show.
Figures released by the Animal Health and Veterinary Laboratories Agency (AHVLA) on Tuesday showed that 58 farms across 11 counties had been affected.
Farms in Norfolk, Suffolk, Essex, Kent, East Sussex, West Sussex, Hertfordshire, Surrey, Hampshire, Cornwall and Wiltshire have all seen confirmed cases.
Of the total, 55 are confirmed cases in sheep and three are in cattle.
The AHVLA said increased reports of the virus in France had prompted it to revise its assessment of areas at higher risk of the disease in the UK, including South Wales.
An agency spokesman said: “Due to the increase in reports of SBV identified in France, the areas at comparatively higher risk in the UK have been revised in line with the plume modeling data from the summer which models areas at risk of midge incursion from northern Europe.
“These areas include Dorset, Devon, Cornwall, Somerset, Gloucestershire and Wiltshire and therefore an increase in risk for South Wales.”
The timing of the most dense plumes would have been in late October for the south-west region, the spokesman added.
“This is therefore in line with the appearance of deformities in lambs being born now, assuming the highest risk period for lambs is if the mother is infected at approximately one month into gestation.”
The majority of cases of Schmallenberg infection in the UK have been diagnosed in sheep to date.
The number of cases of Schmallenberg virus broke though the 1,000 barrier across Europe this week.
The NFU called for co-ordinated action across the EU to develop a rapid field test and a vaccine for the virus.
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