Acute Schmallenberg Virus (SBV) disease in cattle was reported in mainland Europe in 2016, with clinical signs of milk drop fever, sometimes with diarrhoea. Cases of SBV have been reported in cattle and sheep in GB.
Schmallenberg Virus (SBV) is a new disease which was first identified in Germany in 2011. The disease was seen in England in 2012. The first case of SBV in Scotland was identified in 2013 through active surveillance.
The virus is carried principally by midges (Culicoides) and causes disease in cattle and sheep, particularly birth abnormalities in calves and lambs. Birth abnormalities are a result of infection early in cattle (60-172 days) and sheep (28-56 days) pregnancy causing damage to the developing central nervous system of the foetus. This results in brain and limb deformities in newborn lambs and calves. SBV is not a notifiable disease and no restrictions are placed on infected premises.
Farmers are advised to contact their veterinary practitioner or SRUC Veterinary Services if they encounter the following symptoms, and SBV infection is suspected:
Looking at the potential spread of SBV in Scotland
EPIC scientists have highlighted the importance of two risk factors for the spread of SBV in Scotland: environmental temperature and timing of introduction of the disease.
Role of Temperature
Modelling of SBV suggests that risk of spread in Scottish sheep and cattle, under 'the right conditions' is high, but is highly sensitive to temperature. Too early in the season and it will be too cool with insufficient vectors to establish the disease. An introduction of SBV into Scotland later in the summer limits spread on account of the end of the vector season and declining temperatures.
Role of seasonal timing of disease introduction
The most vulnerable time for pregnant ewes carrying spring lambs is December and January. Low levels of midge activity during this time contribute to the small numbers of cases seen in Scotland. Early lambing flocks, where pregnant ewes are present whilst vectors are still active, are most at risk. The lack of SBV being identified in either early lambing flocks or all-year-round calving dairy herds in 2016 suggests the SBV infected midge population likely entered Scotland in late autumn 2016 presumably following a northward progression. The greatest at-risk animals are cattle mated in summer 2016 located in the border counties. The risks of birth abnormalities in cattle following infection are considerably greater due to the greater proportion of the year that cattle are serviced and the greater at-risk window during pregnancy in cattle.
If there is a re-emergence of SBV in Europe, Scottish farmers should consider possible control options, specifically altering the timing of mating or vaccinating if mating is to be during an at-risk period. Vaccinating animals can protect both those vaccinated and other animals by reducing transmission. The option of vaccination is subject to vaccine availability. In conjunction with their vet, farmers should monitor the situation in Europe and their own animals for clinical signs.
Modelling potential for SBV spread in the marginal disease environment of Scotland
SBV spread in Scotland is potentially governed by a number of factors which EPIC’s disease spread models take into account.
Details see Bessell et al., 2013 & Bessell et al., 2014
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