Schmallenberg virus - a new threat to animal health in Europe

The article describes the major findings concerning the occurrence of previously unrecognized infection with a virus provisionally named "Schmallenberg virus" (SBV) in Germany, the Netherlands, Belgium and Great Britain. The virus belongs to the family Bunyaviridae, genus Orthobunyavirus, serogroup Simbu. Full-length genome sequencing has shown its highest genetic similarity to Shamonda and Akabane viruses. The viruses of this group are transmitted mainly by mosquitoes (Culicidae) and midges (Culicoides) with very limited direct transmission from animal to animal (mostly transplacental transmission from a dam to the foetus during pregnancy). The clinical manifestation of the Schmallenberg virus infection has been associated with non-specific clinical signs in adult cattle (fever, reduced milk yield, diarrhoea), whereas congenital malformations (hydrocephalus with brain hypoplasia, arthrogryposis) have been observed in newborn lambs. For diagnostic purposes, RT-PCR, virus neutralisation and indirect immuno-fluorescence tests have been developed. The latter two assays cannot be applied for large-scale testing, but an assay for serological screening is currently unavailable. The major conclusion of the preliminary risk assessment performed by the European Centre for Disease Prevention and Control (ECDC) is that the threat to human health is very unlikely but cannot be excluded at this stage. None of the infections caused by the viruses of the Simbu serogroup are included in the list of diseases subjected to international notification, but affected countries have notified OIE of the occurrence of SBV infections according to regulations applicable to new and emerging diseases.