title: Molecular Characterization of Hemorrhagic Enteritis Viruses (HEV) Detected in HEV-Vaccinated Commercial Turkey Flocks in Germany.
abstract: Despite the application of live hemorrhagic enteritis virus (HEV) vaccines, HEV field outbreaks are suspected to still occur in turkey flocks in Germany. Increasing secondary bacterial infections in HEV-vaccinated flocks suggest that vaccines may be losing efficacy or, possibly, that vaccine strains are causing disease. Thus, the goal of the current study was to investigate the diversity of HEV isolates from fattening turkey flocks between 2008 and 2012 by characterizing the open reading frame (ORF)1 gene at its 5' and 3' ends. Analyses of ORF1 sequences of field isolates and comparison with sequences present in databases revealed that in many cases (13 out of 16 samples), vaccine (avirulent) strains were present. In addition, data indicated the circulation of suspected virulent field isolates and these isolates (3 out of 16) cluster with an early isolate from Germany in the 1980s, but show some mutations in the predicted amino acid (aa) sequences of ORF1 compared to the early isolate. These virulent isolates clearly differ from the spleen-derived avirulent Domermuth vaccine strain used in Germany. In this study, a unique isolate was identified and showed unusual nucleotide mutations that resulted in aa exchanges at the 5' end of ORF1 between aa positions 34 and 174. This genetic drift suggests evolution of HEV including virulent and vaccine-derived strains in the field. This may lead to evasion of vaccinal immunity by drifted viruses and/or an increase in the virulence of field strains.
authors.affiliation: A Clinic for Poultry, University of Veterinary Medicine Hannover, Bünteweg 17, 30559 Hannover, Germany.|B Department of Pathobiology, Ontario Veterinary College, University of Guelph, N1G 2W1 Guelph, Ontario, Canada.
authors.forename: Tamiru Negash
authors.initials: TN
authors.lastname: Alkie
authors.affiliation: C Heidemark GmbH, Veterinary Laboratory, 39340 Haldensleben, Germany.
authors.forename: Ronald
authors.initials: R
authors.lastname: Guenther
authors.affiliation: A Clinic for Poultry, University of Veterinary Medicine Hannover, Bünteweg 17, 30559 Hannover, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Rautenschlein
mesh_terms: D000257:Adenoviridae Infections / Q000517:prevention & control / Q000662:veterinary* / Q000821:virology; D000818:Animals; D005858:Germany; D010802:Phylogeny; D011201:Poultry Diseases / Q000276:immunology / Q000517:prevention & control / Q000821:virology*; D046809:Siadenovirus / Q000145:classification / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D014422:Turkeys / Q000821:virology; D014611:Vaccination; D014764:Viral Proteins / Q000235:genetics / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology
chemical_list: D014764:Viral Proteins; D014765:Viral Vaccines
keywords: ORF1; Siadenovirus; turkey hemorrhagic enteritis virus; vaccination; virulence