title: Experimental Infection of Sheep at 45 and 60 Days of Gestation with Schmallenberg Virus Readily Led to Placental Colonization without Causing Congenital Malformations.
abstract: BACKGROUND
  Main impact of Schmallenberg virus (SBV) on livestock consists in reproductive disorders, with teratogenic effects, abortions and stillbirths. SBV pathogenesis and viral placental crossing remain currently poorly understood. Therefore, we implemented an experimental infection of ewes, inoculated with SBV at 45 or 60 days of gestation (dg).
  
  
  METHODS
  "Mourerous" breed ewes were randomly separated in three groups: eight and nine ewes were subcutaneously inoculated with 1 ml of SBV infectious serum at 45 and 60 dg, respectively (G45 and G60). Six other ewes were inoculated subcutaneously with sterile phosphate buffer saline as control group. All SBV inoculated ewes showed RNAemia consistent with previously published studies, they seroconverted and no clinical sign was reported. Lambs were born at term via caesarian-section, and right after birth they were blood sampled and clinically examined. Then both lambs and ewes were euthanatized and necropsied.
  No lambs showed any malformation suggestive of SBV infection and none of them had RNAemia or anti-SBV antibodies prior to colostrum uptake. Positive SBV RNA detection in organs was rare in both G45 and G60 lambs (2/11 and 1/10, respectively). Nevertheless most of the lambs in G45 (9/11) and G60 (9/10) had at least one extraembryonic structure SBV positive by RTqPCR. The number of positive extraembryonic structures was significantly higher in G60 lambs. Time of inoculation (45 or 60 dg) had no impact on the placental colonization success rate but affected the frequency of detecting the virus in the offspring extraembryonic structures by the time of lambing. SBV readily colonized the placenta when ewes were infected at 45 or 60 dg but infection of the fetuses was limited and did not lead to congenital malformations.
authors.affiliation: Research Unit of Epidemiology and Risk Analysis Applied to Veterinary Sciences (UREAR-ULg), Fundamental and Applied Research for Animals & Health (FARAH), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Martinelle
authors.affiliation: Research Unit of Epidemiology and Risk Analysis Applied to Veterinary Sciences (UREAR-ULg), Fundamental and Applied Research for Animals & Health (FARAH), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium; Operational Directorate Viral Diseases, Veterinary and Agrochemical Research Centre (CODA-CERVA), Brussels, Belgium.
authors.forename: Antoine
authors.initials: A
authors.lastname: Poskin
authors.affiliation: Research Unit of Epidemiology and Risk Analysis Applied to Veterinary Sciences (UREAR-ULg), Fundamental and Applied Research for Animals & Health (FARAH), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Dal Pozzo
authors.affiliation: Operational Directorate Viral Diseases, Veterinary and Agrochemical Research Centre (CODA-CERVA), Brussels, Belgium.
authors.forename: Nick
authors.initials: N
authors.lastname: De Regge
authors.affiliation: Operational Directorate Viral Diseases, Veterinary and Agrochemical Research Centre (CODA-CERVA), Brussels, Belgium.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Cay
authors.affiliation: Research Unit of Epidemiology and Risk Analysis Applied to Veterinary Sciences (UREAR-ULg), Fundamental and Applied Research for Animals & Health (FARAH), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium.
authors.forename: Claude
authors.initials: C
authors.lastname: Saegerman
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D002044:Bunyaviridae Infections / Q000097:blood / Q000662:veterinary / Q000821:virology*; D002522:Chlorocebus aethiops; D000013:Congenital Abnormalities / Q000662:veterinary / Q000821:virology*; D005260:Female; D005865:Gestational Age; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary; D008297:Male; D016851:Orthobunyavirus / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D010920:Placenta / Q000821:virology*; D011247:Pregnancy; D012367:RNA, Viral / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012756:Sheep; D012757:Sheep Diseases / Q000175:diagnosis / Q000635:transmission / Q000821:virology*; D013997:Time Factors; D014709:Vero Cells
chemical_list: D000914:Antibodies, Viral; D012367:RNA, Viral