title: The PB2, PA, HA, NP, and NS genes of a highly pathogenic avian influenza virus A/whooper swan/Mongolia/3/2005 (H5N1) are responsible for pathogenicity in ducks.
abstract: BACKGROUND
  Wild ducks are the natural hosts of influenza A viruses. Duck influenza, therefore, has been believed inapparent infection with influenza A viruses, including highly pathogenic avian influenza viruses (HPAIVs) in chickens. In fact, ducks experimentally infected with an HPAIV strain, A/Hong Kong/483/1997 (H5N1) (HK483), did not show any clinical signs. Another HPAIV strain, A/whooper swan/Mongolia/3/2005 (H5N1) (MON3) isolated from a dead swan, however, caused neurological dysfunction and death in ducks.
  
  
  METHODS
  To understand the mechanism whereby MON3 shows high pathogenicity in ducks, HK483, MON3, and twenty-four reassortants generated between these two H5N1 viruses were compared for their pathogenicity in domestic ducks.
  
  
  RESULTS
  None of the ducks infected with MON3-based single-gene reassortants bearing the PB2, NP, or NS gene segment of HK483 died, and HK483-based single-gene reassortants bearing PB2, NP, or NS genes of MON3 were not pathogenic in ducks, suggesting that multiple gene segments contribute to the pathogenicity of MON3 in ducks. All the ducks infected with the reassortant bearing PB2, PA, HA, NP, and NS gene segments of MON3 died within five days post-inoculation, as did those infected with MON3. Each of the viruses was assessed for replication in ducks three days post-inoculation. MON3 and multi-gene reassortants pathogenic in ducks were recovered from all of the tissues examined and replicated with high titers in the brains and lungs.
  
  
  CONCLUSIONS
  The present results indicate that multigenic factors are responsible for efficient replication of MON3 in ducks. In particular, virus growth in the brain might correlate with neurological dysfunction and the disease severity.
authors: Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.
authors: Masahiro
authors: M
authors: Kajihara
authors: Yoshihiro
authors: Y
authors: Sakoda
authors: Kosuke
authors: K
authors: Soda
authors: Kenji
authors: K
authors: Minari
authors: Masatoshi
authors: M
authors: Okamatsu
authors: Ayato
authors: A
authors: Takada
authors: Hiroshi
authors: H
authors: Kida
mesh_terms: D000818:Animals; D004372:Ducks; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000378:metabolism*; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity* / Q000502:physiology; D005585:Influenza in Birds / Q000821:virology*; D019590:Nucleocapsid Proteins; D011201:Poultry Diseases / Q000821:virology*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D016865:Reassortant Viruses / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014774:Virulence; D014779:Virus Replication
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; C048842:NP protein, Influenza A virus; C108309:NS protein, influenza virus; D019590:Nucleocapsid Proteins; C061290:PA protein, influenza viruses; C502893:PB2 protein, influenza virus; D016601:RNA-Binding Proteins; D014758:Viral Core Proteins; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins; C109963:hemagglutinin, avian influenza A virus; D012324:RNA-Dependent RNA Polymerase
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