Schmallenberg in Scotland: a Year in Review

Schmallenberg virus (SBV) is a member of the Simbu serogroup of the Orthobunyavirus family similar to other pathogens including Akabane and Shamonda viruses originating from areas of Asia, Africa and Australasia. These virus groups are vector borne and transmitted by biting midges. SBV virus can infect several ruminant species and was first identified in Europe in 2011. It was first detected in the UK in 2012 with clustered outbreaks in 2016-2017 and then from 2021 onwards. Although cases of disease caused by SBV have been reported consistently in England and Wales in previous years, Scottish herds and flocks have remained largely unaffected until 2025. Cases have been reported in early lambing flocks in the spring of 2025 in the Southwest and the central belt of Scotland with evidence and anecdote of exposure being more widespread throughout ruminant management systems across Scotland. The emergence or re-emergence of SBV in Scotland has not only had significant impact at the individual farm level but has also raised concerns with the increased risk of wider vector borne disease spread throughout Scotland in the future. Bluetongue virus (BTV) shares the same vector and can share some similar clinical signs but unlike SBV is notifiable. There have been no reports of incursion of BTV into Scotland and continued surveillance relies on vets being informed of any suspicion of BTV. At the time of submission, the critical period of exposure to SBV in Scotland is likely to have been July to September 2024 although a mild autumn may have led to prolonged midge exposure into November, having the potential to impact flocks and herds further into the spring/summer 2025. This presentation will highlight case material submitted to SRUC disease surveillance centres throughout 2025 related to SBV outbreaks in ruminant species (dairy, beef, sheep) as well as contain material discussed by VIO’s relating to the investigation of abortion, poor fertility or production parameters where SBV was considered a differential diagnosis.