Cases of Schmallenberg virus (SBV) infection have been confirmed in two separate Scottish flocks close to the border with England.
The confirmation from SAC Consulting Veterinary Services (part of Scotland’s Rural College) that malformed lambs were discovered in two flocks follows increasing numbers of affected lambs identified in England and Wales through the winter.
SBV is spread by midges and, if infection occurs for the first time early in sheep and cattle pregnancies, damage to the developing central nervous system occurs. This results in brain and limb deformities in the newborn lambs and calves.
Difficult to predict
Head of SAC Consulting Veterinary Services George Caldow said: “It can be difficult to predict how widespread any infection will turn out to have been or to be, but there are some important points that give us an indication of the likely impact SBV infection will have this spring on Scottish livestock.
“In winter 2016-2017, SRUC vets have not diagnosed SBV in either early lambing flocks in Scotland or in all-year-round calving dairy herds in Scotland.
“It is, therefore, inferred that at the time of maximum midge activity in 2016 there was unlikely to have been SBV present in the midges in Scotland, otherwise we would have seen cases in these two categories of animals.
“The midge population progressively declines as we move in to winter and midge numbers will have been low during the time of maximum vulnerability of the main Scottish spring lambing flock, which is likely to have been December and January. Therefore, it may be only a small number of ewes will have been infected, with a few affected lambs being born and these are more likely to be in flocks in the southernmost part of the country.”
Mr Caldow added: “The limited information we have to date suggests that the midge population in some parts of southern Scotland became infected in late autumn probably due to the gradual spread north of infected midges.”
SAC Consulting vets expect the higher risk will be to cattle mated in the summer of 2017 and at the edge of the northward progression of infected midges.
- A Schmallenberg virus (SBV) Q&A can be downloaded from the Scottish Government website.