title: Serological testing of Schmallenberg virus in Swedish wild cervids from 2012 to 2016.
abstract: BACKGROUND
  Schmallenberg virus (SBV) first emerged in Europe in 2011, and in Sweden in late 2012. The virus was still circulating in parts of Europe in 2015. In recent testing, the virus has not been detected in Swedish domestic animals, indicating that it is no longer circulating in Sweden. It is not known if the virus has circulated and is still circulating in Swedish wild cervid populations and whether wildlife can act as virus reservoirs. The aim of this study was to investigate whether SBV has circulated, and is still circulating among wild cervids in Sweden.
  
  
  RESULTS
  Ninety-two sera from moose (Alces alces, n = 22), red deer (Cervus elaphus, n = 15), fallow deer (Dama dama, n = 44), and roe deer (Capreolus capreolus, n = 11) were collected and analyzed for antibodies against SBV. The sampling occurred in the southern and middle part of Sweden during three time periods: 1) before the vector season in 2012, 2) after the vector season in 2012, and 3) after the vector season in 2015. Animals from periods 1 and 2 were of varying ages, whereas animals collected in period 3 were born after the vector season 2013. Animals from period 1 (n = 15) and 3 (n = 47) were seronegative, but, 53% (16 of 30) of animals from period 2 were seropositive, determined by SBV competitive ELISA. Samples from period 2 were additionally analyzed for SBV-neutralizing antibodies. Such antibodies were detected in 16/16 SBV-N-antibody-positive, 3/12 negative and 2/2 doubtful sera. The two tests were in accordance at SBV-neutralizing antibody titers of 1:32 or higher.
  
  
  CONCLUSIONS
  Our results show that SBV circulated among wild cervids during the vector season of 2012. Three years later, no SBV-antibodies were detected in animals born after the vector season 2013. The likely absence of SBV circulation in Sweden, in contrast to other parts of Europe, might be explained by the annual occurrence of a vector-free season due to climate conditions. Interpretations are limited by the small sample-size, but the results suggest that the SBV competitive ELISA has high specificity but might have slightly lower sensitivity compared to a seroneutralization assay, when using samples from wild cervids.
authors.affiliation: Department of Clinical Sciences, Division of Reproduction, Swedish University of Agricultural Sciences, Box 7054, 750 07, Uppsala, Sweden. anna.malmsten@slu.se.
authors.forename: A
authors.initials: A
authors.lastname: Malmsten
authors.affiliation: Department of Pathology and Wildlife Diseases, National Veterinary Institute, 751 89, Uppsala, Sweden.|Department of Wildlife, Fish, and Environmental studies, Swedish University of Agricultural Sciences, 901 83, Umeå, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Malmsten
authors.affiliation: Department of Microbiology, National Veterinary Institute, 751 89, Uppsala, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Blomqvist
authors.affiliation: Department of Microbiology, National Veterinary Institute, 751 89, Uppsala, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Näslund
authors.affiliation: Department of Microbiology, National Veterinary Institute, 751 89, Uppsala, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Vernersson
authors.affiliation: Department of Clinical Sciences, Host Pathogen Interaction Group, DOS, Swedish University of Agricultural Sciences, Box 7054, 750 07, Uppsala, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Hägglund
authors.affiliation: Department of Clinical Sciences, Division of Reproduction, Swedish University of Agricultural Sciences, Box 7054, 750 07, Uppsala, Sweden.
authors.forename: A-M
authors.initials: AM
authors.lastname: Dalin
authors.affiliation: Department of Pathology and Wildlife Diseases, National Veterinary Institute, 751 89, Uppsala, Sweden.
authors.forename: E O
authors.initials: EO
authors.lastname: Ågren
authors.affiliation: Department of Clinical Sciences, Host Pathogen Interaction Group, DOS, Swedish University of Agricultural Sciences, Box 7054, 750 07, Uppsala, Sweden.|Department of Clinical Sciences, Host Pathogen Interaction Group, Ruminant medicine, Swedish University of Agricultural Sciences, Box 7054, 750 07, Uppsala, Sweden.
authors.forename: J-F
authors.initials: JF
authors.lastname: Valarcher
mesh_terms: D000818:Animals; D000835:Animals, Wild; D002044:Bunyaviridae Infections / Q000453:epidemiology / Q000662:veterinary*; D003670:Deer / Q000821:virology*; D004797:Enzyme-Linked Immunosorbent Assay; D007303:Insect Vectors / Q000821:virology; D016851:Orthobunyavirus / Q000276:immunology*; D012698:Serologic Tests / Q000662:veterinary; D013548:Sweden / Q000453:epidemiology
keywords: Fallow deer; Moose; Orthobunyavirus; Red deer; Roe deer; SBV; Scandinavia; Serology; Wildlife