Transmission of Schmallenberg virus in a housed dairy herd in the UK

Schmallenberg virus (SBV) is a recently emerged Orthobunyavirus of ruminants originally discovered in 2011 near the town of Schmallenberg in Germany (Hoffmann and others 2012). SBV appears to have entered Europe in the summer of 2011 and has since spread rapidly across much of central and northern Europe. Seroprevalence in some areas has been reported close to 100 per cent (Tarlinton and others 2012, Meroc and others 2013). Viruses closely related to SBV are known to be transmitted by Culicoides biting midges (Jennings and Mellor 1989), and field studies have shown the presence of SBV RNA in Culicoides species in several affected countries (Rasmussen and others 2012, Elbers and others 2013). SBV infection is associated with abortion and malformations in cattle and sheep, and has been shown to be neurotropic in lambs and calves infected in utero (van den Brom and others 2012, Varela and others 2013). In dairy cattle, an ‘acute’ form of the disease associated with a drop in milk yield, diarrhoea and mild pyrexia has also been observed. Here we report a within-herd study on a typical dairy farm located in southern England during 2012. The farm runs a dairy herd comprising approximately 230 Holstein cows, approximately 150 of which represent a milking herd. Importantly, no animals were imported onto the farm during the period of this study. In February 2012, a cow (#157) aborted close to term. Suspecting SBV as the cause of abortion, we sampled the affected cow as well as nine additional animals using an indirect SBV antibody ELISA (IDvet). All animals were seronegative for SBV with the exception of cow #157 (Fig 1a). An identical result was obtained upon repeat testing using a second set of blood samples. We further confirmed the presence of anti-SBV antibodies by virus neutralisation assay (Loeffen and others 2012) (data not shown), and immunofluorescence using Short Communication