title: Inferences about the transmission of Schmallenberg virus within and between farms.
abstract: In the summer of 2011 Schmallenberg virus (SBV), a Culicoides-borne orthobunyavirus, emerged in Germany and The Netherlands and subsequently spread across much of Europe. To draw inferences about the transmission of SBV we have developed two models to describe its spread within and between farms. The within-farm model was fitted to seroprevalence data for cattle and sheep farms in Belgium and The Netherlands, with parameters estimated using approximate Bayesian computation. Despite the short duration of viraemia in cattle and sheep (mean of 3-4 days) the within-farm seroprevalence can reach high levels (mean within-herd seroprevalence >80%), largely because the probability of transmission from host to vector is high (14%) and SBV is able to replicate quickly (0.03 per day-degree) and at relatively low temperatures (threshold for replication: 12.3°C). Parameter estimates from the within-farm model were then used in a separate between-farm model to simulate the regional spread of SBV. This showed that the rapid spread of SBV at a regional level is primarily a consequence of the high probability of transmission from host to vector and the temperature requirements for virus replication. Our results, obtained for a region of the UK in a typical year with regard to animal movements, indicate that there is no need to invoke additional transmission mechanisms to explain the observed patterns of rapid spread of SBV in Europe. Moreover, the imposition of movement restrictions, even a total movement ban, has little effect on the spread of SBV at this scale.
authors.affiliation: The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK. Electronic address: simon.gubbins@pirbright.ac.uk.
authors.forename: Simon
authors.initials: S
authors.lastname: Gubbins
authors.affiliation: Department of Epidemiology and Population Health, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Chester High Road, Neston, Cheshire CH64 7TE, UK.
authors.forename: Joanne
authors.initials: J
authors.lastname: Turner
authors.affiliation: Department of Epidemiology and Population Health, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Chester High Road, Neston, Cheshire CH64 7TE, UK.
authors.forename: Matthew
authors.initials: M
authors.lastname: Baylis
authors.affiliation: Unit of Co-ordination Veterinary Diagnosis-Epidemiology and Risk Assessment, CODA-CERVA, Groeselenberg 99, 1180 Brussels, Belgium; Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Yves
authors.initials: Y
authors.lastname: van der Stede
authors.affiliation: GD Animal Health, Arnsbergstraat 7, 7413EZ Deventer, The Netherlands.
authors.forename: Gerdien
authors.initials: G
authors.lastname: van Schaik
authors.affiliation: European Food Safety Authority, Via Carlo Magno 1A, 43126 Parma, Italy.
authors.forename: José Cortiñas
authors.initials: JC
authors.lastname: Abrahantes
authors.affiliation: The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Wilson
mesh_terms: D000383:Agriculture; D000818:Animals; D001499:Bayes Theorem; D001530:Belgium / Q000453:epidemiology; D002044:Bunyaviridae Infections / Q000097:blood / Q000453:epidemiology / Q000635:transmission / Q000662:veterinary*; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D002519:Ceratopogonidae / Q000821:virology; D007303:Insect Vectors / Q000821:virology; D009426:Netherlands / Q000453:epidemiology; D016851:Orthobunyavirus / Q000472:pathogenicity; D016036:Seroepidemiologic Studies; D012756:Sheep; D012757:Sheep Diseases / Q000097:blood / Q000453:epidemiology / Q000635:transmission* / Q000821:virology
keywords: Approximate Bayesian computation; Epidemiology; Modelling; SBV; Vector-borne disease