Schmallenberg virus

Schmallenberg virus (SBV) causes congenital malformations and stillbirths in cattle, sheep, goats, bison and possibly camelids.

The virus was first characterised in November 2011 in Germany from samples from diseased dairy cattle. The virus was named after Schmallenberg, in North Rhine-Westphalia, Germany, from where the first definitive sample was derived. Later on, after Germany, the virus was detected throughout Europe and surrounding countries.

Transmission

Based on the current available information, experts concluded that the risk for human health is negligible. The viraemic period of Schmallenberg virus is short and the virus is transmitted by biting midges, with apparent similarity to the vector transmission of bluetongue virus. The risk of disease spread from trade in meat and milk is negligible. For semen, embryos and live animals research institutes have made recommendations for safe trade.

Diagnosis

Experimental infection in cattle and sheep showed no clinical signs or mild symptoms at 3 to 5 days post-inoculation with an incubation period of between 1 and 4 days and viraemia lasting for 1 to 5 days.

Since early December 2011, congenital malformations have been reported in newborn lambs in countries in Northwest Europe, and SBV was detected in and isolated from the brain tissue. Stillbirth and congenital malformations with PCR positive results have also been reported now throughout Europe and surrounding countries.

Manifestation of clinical signs varies by species: bovine adults have shown a mild form of acute disease during the vector season, congenital malformations have affected more species of ruminants, in particular sheep and goat. From some sheep and cow farms diarrhoea was also reported.