Following the request from the European Commission for EFSA to continue to collect data and provide updates of the epidemiological situation on Schmallenberg virus (SBV) in the EU, data received during the reporting period was analysed, updating the previously published report on the analysis of the epidemiological data and preliminary assessment of impact.
The analysis intends to give an overview of the SBV situation (reporting period from 1 August 2011 till 30 April 2013) together with an update of newly affected herds.
Most countries in Europe have reported SBV cases. It can be seen that in winter 2012 and spring 2013 the area where cases were reported has expanded. In the north the area in the United Kingdom has extended to Scotland, and in the Scandinavia mainland regions of Norway, Finland and Sweden are now affected. SBV has also spread to new regions in the east of Europe: Estonia, Latvia, Hungary, Slovenia and Croatia.
Cattle, sheep, goats, alpacas, bison, buffalos, camels, horses, llamas, moose, fallow deer roe deer and red deer have also been tested for SBV. SBV has been detected by RT-PCR in bison, deer and moose, plus alpacas, buffalos as well as cattle, sheep and goats; fallow deer roe deer and red deer have been found to be seropositive.
Acute cases in adult animals and arthrogryposis hydranencephaly syndrome (AHS) cases in foetuses and neonates (not all confirmed by laboratory testing) are still being observed in 2013. Acute adult cases in Germany were observed in all months from November 2012 to April 2013 suggesting virus circulation during the winter period. AHS cases are being reported in newly affected areas. In some of the previously affected countries the affected area is still expanding. Areas on the periphery of previously affected countries may have a lower prevalence and therefore susceptible animals may be present. There is no apparent evidence to refute the assumption that SBV infection results in long term immunity, but vigilance for evidence to the contrary is important.
Temporal analysis of cases with laboratory confirmation by pathogen detection shows the outbreak evolution over time. Serological results were excluded since the serological detection of SBV antibodies can only be used as evidence of infection and provide no information on whether detected cases are in the clinical phase of the disease (i.e. new occurrence) or correspond to a previous infection. Since September 2011 there has been no period where new SBV cases have not been detected, any temporal variation is most probably due to production practices in the affected species.
In the previous report (EFSA Nov 2012) a between herd impact assessment based upon the comparison between SBV confirmed herds and the total number of herds in each affected region by species was made. For all affected countries, the number of SBV confirmed herds was estimated to be low compared with the total number of herds. Nevertheless, under reporting or lack of confirmation was noted to affect the ratio. Considering the possibility of high under ascertainment the analysis previously done may not provide any additional information regarding between herd impact of the infection.