Spread of Schmallenberg virus infections in the ruminants in Poland between 2012 and 2013

The aim of the study was to evaluate the prevalence of Schmallenberg virus (SBV) specific antibodies in ruminants from 13 Polish provinces, sampled between January 2010 and August 2013. A total number of 1813 serum samples from cattle, sheep, goats, mouflon, wild and farmed cervids, and European bison were tested by ELISA for viral nucleoprotein antibodies. First SBV seropositive animals were identified in August 2012 (1.6%), and the percentage increased gradually, reaching 57.1% in December of this year. The proportion of seropositive animals in 2013 at the level of 34.2% increased tenfold in comparison to 2012 (3.4%), which was particularly significant at the level of individual provinces. In 2013, the highest percentages of SBV seropositive animals were found in Dolnoslaskie (92.3%), Podlaskie (82.3%), and Zachodniopomorskie (80.9%) provinces. Significant associations between the seroprevalence and province of origin, month, ruminant species, and insect vector activity were found, while no dependence of animal age on seropositivity was observed. The differences between SBV seropositive large and small ruminants suggested the involvement of some vector exposure factors, which needs to be further investigated.