Schmallenberg virus: on its way out or due for a comeback?

SCHMALLENBERG virus (SBV) emerged during the summer of 2011 in north-western Europe and was identified for the first time in dairy cattle herds in Germany (Hoffmann and others 2012). The virus belongs to the Simbu serogroup of Orthobunyaviruses and many similarities have been reported with the closely related Akabane virus regarding its transmission, pathogenesis and induced clinical signs. SBV causes mild clinical signs in adult ruminants, ranging from fever, diarrhoea and temporarily reduced milk production. However, infection of pregnant cattle, sheep and goats can cause transplacental transmission leading months later to abortions, stillbirths and congenital malformations characterised by the arthrogryposis-hydranencephaly syndrome in newborns (Doceul and others 2013). After its first identification in Germany in 2011, SBV spread rapidly and widely over a large part of Europe, including the UK (EFSA 2014). Indigenous European Culicoides biting midges, which were already known to have spread bluetongue virus serotype 8 after its emergence in Europe in 2006 (Mehlhorn and others 2007, Meiswinkel and others 2007), were found to be responsible for the rapid transmission of SBV (De Regge and others 2012, 2015). Seroprevalence studies showed that the majority of domestic ruminants became infected in SBV-affected countries (Meroc and others 2013, 2014, Wernike and others 2014). In 2012, SBV spread further over Europe and evidence for renewed but lower levels of SBV circulation in countries affected in 2011 was found (Conraths and others 2013, Afonso and others 2014, De Regge and others 2014). From spring 2013 onwards, the number …