Schmallenberg virus

Schmallenberg virus is the informal name given to a recently isolated orthobunyavirus, which has not been given a formal name as of January 2013, initially reported in October 2011 to cause congenital malformations and stillbirths in cattle, sheep, goats, and possibly alpaca. It appears to be transmitted by midges (Culicoides spp.) which are likely to have been most active in causing the infection in the northern hemisphere summer and autumn of 2011, with animals subsequently giving birth from late 2011. Schmallenberg virus falls in the Simbu serogroup of Orthobunyaviruses; as of January 2013, it is considered to be most closely related to the Sathuperi and Douglas viruses. The virus is named after Schmallenberg, in North Rhine-Westphalia, Germany, from where the first definitive sample was derived. After Germany, it has also been detected in the Netherlands, Belgium, France, Luxembourg, Italy, Spain, the United Kingdom, Switzerland, Ireland, Finland, Denmark, Sweden, Austria, Norway, Poland and Estonia. The virus has been recognised by the European Commission's Standing Committee on the Food Chain and Animal Health and the Friedrich-Loeffler-Institut (German Research Institute for Animal Health). A risk assessment in December 2011 did not consider it likely to be a threat to human health, as other comparable viruses are not zoonotic. Immunity can possibly be acquired naturally against SBV. It is possible that the seasonality of the infection cycle would not entail a second epidemic circulation next year, due to the shortness of the viraemic period (about 4 to 6 days post exposure, longer in affected foetuses). Vaccination is a possible option for controlling the disease as a vaccine exists for the similar Akabane virus. In March 2012, scientists of the Friedrich-Loeffler-Institut first succeeded in producing an electron microscope image of the Schmallenberg virus. The genetic structure of Schmallenberg virus is typical for Bunyavirales viruses, which are a family of enveloped negative-sense single stranded RNA viruses with a genome split into three parts—Small (S), Medium (M) and Large (L). The L RNA segment encodes an RNA-dependent RNA polymerase (L protein), the M RNA segment encodes two surface glycoproteins (Gc and Gn) and a nonstructural protein (NSm), while the S RNA segment encodes a nucleocapsid protein (N) and, in an alternative overlapping reading frame, a second nonstructural protein (NSs). The genomic RNA segments are encapsidated by copies of the N protein in the form of ribonucleoprotein (RNP) complexes. The N protein is the most abundant protein in virus particles and infected cells and, therefore, the main target in many serological and molecular diagnostics.