open access

https://doi.org/10.14943/doctoral.r6754

https://hdl.handle.net/2115/44514

水禽の羽におけるH5N1 亜型高病原性鳥インフルエンザ ウイルスの増殖に関する研究

英語

2010-12-24

Hokkaido University

iv, 70p.

Asian lineage H5N1 highly pathogenic avian influenza (HPAI) virus has spread from Asia to Europe, the Middle East, and Africa, causing profound economic losses in the poultry industry. Several reports of virus detection in wild and domestic waterfowl indicate that waterfowl can serve as carriers and amplifying hosts of this virus. Therefore, the author hypothesized that the detailed analysis on the pathogenesis and viral replication in waterfowl would provide information to reduce the risk of viral transmission from infected waterfowl. In particular, the author focused on the viral replication in feathers, and discussed the possible role of waterfowl feathers in viral transmission from infected birdsIn chapter Ⅰ, the author examined the pathogenesis in domestic ducks inoculated with Japanese H5N1 HPAI virus. The virus caused mortality, neurologic symptoms, and pathologic changes such as the encephalitis, pancreatic necrosis, corneal opacity and epidermal necrosis of the feathers. High mortality in ducklings indicates that the age of birds is a factor influencing on the viral replication. The feather lesions caused by virus replication raise the potential of feathers as new route of virus shedding from waterfowl infected with H5N1 HPAI virus. In chapter Ⅱ, the experimental infection was performed to examine whether the feather lesion observed in the previous chapter is common to other H5N1 HPAI virus strains or other waterfowl species. Two different clades of the virus replicated in the feather epidermis of domestic ducks and geese in experimental infection. Electron microscopic examination provided the direct evidence of viral replication in feather epidermal cells. Viral replication in the feather tissue was also found in whooper swans naturally infected with the virus. In addition, the viral transmission was confirmed in domestic ducks by oral inoculation of down feathers plucked from a duck infected with the virus. In chapter Ⅲ, it was reported that feathers of infected domestic ducks can be useful samples for virus detection as well as their swabs. In the experimental infection using 2 H5N1 HPAI viruses and domestic ducks, larger amounts of viruses were isolated for longer period from feathers than from the swabs, indicating that feathers are considered to be useful clinical samples for surveillance or diagnostic examination of H5N1 HPAI virus in domestic ducks. The author also investigated the viral persistence in feathers detached from bodies of domestic ducks infected with H5N1 HPAI viruses to evaluate the possible environmental contamination by infective feathers. Feathers plucked from experimentally infected domestic ducks were examined by virus isolation. Infectious viruses persisted for the longest period in feather calami compared with drinking water and feces. Viral infectivity persisted in the feathers for 160 days at 4oC and for 15 days at 20oC. These results indicate that feathers detached from domestic ducks infected with H5N1 HPAI virus can function as fomites containing high viral loads in the environment.In conclusion, the author presented a new viewpoint on an epidemiological role of waterfowl feathers in Asian lineage H5N1 HPAI virus transmission.

2010-12-24

乙第6754号

博士(獣医学)

博士論文

Version of Record