Schmallenberg virus has been identified in Finland for the first time in lambs. Previously, only antibodies of the virus have been found in Finland. Discovery of the virus is not unexpected, as antibody studies indicated that the virus has become widespread in Finland during the summer and autumn 2012. The virus does not affect humans.
The virus was identified using the PCR method at the Finnish Food Safety Authority Evira in three deformed lambs, all from the same flock and born at full term at the end of December. The ewes had been infected at the end of August or early September in the early stages of pregnancy. The lambs had arthrogryposis of the limbs, either straight of flexed, and hydrocephalus, which are typical deformities caused by the Schmallenberg virus. Deformed lambs are not viable.
Since the Schmallenberg virus has spread into Finland in summer and autumn 2012, it is expected that deformed lambs are born between December and February and calves most likely in the period between March and May. The virus is spread by midges from one ruminant to another. When the temperatures drop, midges become inactive and the spread of the virus stops. The risk of deformities concerns lambs born between December and February, as midges were active at the start of the ewe’s pregnancy. Most lambs are usually born later, in March-May.
The virus causes symptoms as it spreads to new areas, where ruminants do not have protection created by the infection. If the virus is endemic, ruminants are usually infected at such an early age that they are protected before the first pregnancy.
It is not known at present whether or not the virus is capable of overwintering in Finland. It is likely that midges carrying the virus will continue to arrive in Finland carried by southerly and south-westerly winds.