The National Institute of Animal Health, NARO (NIAH) performed the full-genome sequence analysis of highly pathogenic avian influenza virus (HPAIV) which isolated from an outbreak in Kagawa Prefecture in January 2018. It was revealed that this virus underwent a gene reassortment between an H5N8 virus that was epidemic in Europe last year and an HxN6 virus in wild birds. Intervention against the intrusion of HPAIVs which are carried by wild birds into poultry farms is needed to prevent HPAI in poultry.
NIAH clarified that a causative agent of HPAI occurred in Kagawa Prefecture on 11 January 2018 is an HPAIV of H5N6 subtype (Kagawa isolate). This virus showed high mortality against chickens within 24 hours by intravenous inoculation test which prescribed by the Organization for Animal Health (OIE).
Full-genome sequence analysis and comparison of the sequences obtained with those publicized in the database show that 7 of the 8 gene segments of this isolate are derived from an H5N8 subtype HPAIV that was prevalent in Europe the last year. Neuraminidase (NA) gene is derived from an HxN6 subtype avian influenza virus (Hx means unknown HA subtype) which have perpetuated in wild birds of the Eurasian continent. Although this isolate is genetically related to the H5N6 subtype HPAIV isolated from a dead wild mute swan (Cygnus olor) in Shimane Prefecture in November 2017, it is genetically distinguishable. These results suggest that there have been at least 2 different intrusions of H5N6 HPAIVs in Japan during this winter.
The virus isolate in Kagawa prefecture doesn't have amino acid mutation which causes the resistance against NA inhibitor as an antiviral agent. In addition, there was no amino acid mutation which is known to enhance/increase the infectivity to mammals.The NIAH will perform further research work with this virus.