title: Avian influenza H7N9/13 and H7N7/13: a comparative virulence study in chickens, pigeons, and ferrets.
abstract: Human influenza cases caused by a novel avian H7N9 virus in China emphasize the zoonotic potential of that subtype. We compared the infectivity and pathogenicity of the novel H7N9 virus with those of a recent European avian H7N7 strain in chickens, pigeons, and ferrets. Neither virus induced signs of disease despite substantial replication in inoculated chickens and rapid transmission to contact chickens. Evidence of the replication of both viruses in pigeons, albeit at lower levels of RNA excretion, was also detected. No clear-cut differences between the two H7 isolates emerged regarding replication and antibody development in avian hosts. In ferrets, in contrast, greater replication of the avian H7N9 virus than of the H7N7 strain was observed with significant differences in viral presence, e.g., in nasal wash, lung, and cerebellum samples. Importantly, both viruses showed the potential to spread to the mammal brain. We conclude that efficient asymptomatic viral replication and shedding, as shown in chickens, facilitate the spread of H7 viruses that may harbor zoonotic potential. Biosafety measures are required for the handling of poultry infected with avian influenza viruses of the H7 subtype, independently of their pathogenicity for gallinaceous poultry.
  
  
  OBJECTIVE
  This study is important to the field since it provides data about the behavior of the novel H7N9 avian influenza virus in chickens, pigeons, and ferrets in comparison with that of a recent low-pathogenicity H7N7 strain isolated from poultry. We clearly show that chickens, but not pigeons, are highly permissive hosts of both H7 viruses, allowing high-titer replication and virus shedding without any relevant clinical signs. In the ferret model, the potential of both viruses to infect mammals could be demonstrated, including infection of the brain. However, the replication efficiency of the H7N9 virus in ferrets was higher than that of the H7N7 strain. In conclusion, valuable data for the risk analysis of low-pathogenicity avian influenza viruses of the H7 subtype are provided that could also be used for the risk assessment of zoonotic potentials and necessary biosafety measures.
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
authors.forename: Donata
authors.initials: D
authors.lastname: Kalthoff
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
authors.forename: Jessica
authors.initials: J
authors.lastname: Bogs
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Grund
authors.affiliation: Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Tauscher
authors.affiliation: Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
authors.forename: Jens P
authors.initials: JP
authors.lastname: Teifke
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Starick
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany.
authors.forename: Timm
authors.initials: T
authors.lastname: Harder
authors.affiliation: Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany martin.beer@fli.bund.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Beer
mesh_terms: D000328:Adult; D000818:Animals; D001717:Birds / Q000821:virology; D002645:Chickens / Q000821:virology*; D002681:China; D010856:Columbidae / Q000821:virology*; D005260:Female; D005289:Ferrets / Q000821:virology*; D006801:Humans; D053126:Influenza A Virus, H7N7 Subtype / Q000235:genetics*; D064766:Influenza A Virus, H7N9 Subtype / Q000235:genetics*; D005585:Influenza in Birds / Q000235:genetics / Q000821:virology; D007251:Influenza, Human / Q000235:genetics / Q000821:virology; D009976:Orthomyxoviridae Infections / Q000235:genetics / Q000821:virology; D012367:RNA, Viral / Q000235:genetics; D014774:Virulence / Q000235:genetics*; D014779:Virus Replication / Q000235:genetics; D017201:Virus Shedding / Q000235:genetics
chemical_list: D012367:RNA, Viral