-Highly pathogenic avian influenza virus-
The National Institute of Animal Health, NARO (NIAH) had conducted a whole-genome sequence analysis of the virus that caused the Highly Pathogenic Avian Influenza Virus (HPAIV) outbreak on 5 and 8 November in Kagawa prefecture, Japan. Investigation suggests the HPAIV from the outbreak in Europe last winter was brought into Japan by migratory birds flying over the Eurasian continent this year. Poultry farmers need to be extra cautious not to let the wild birds bring the HPAIV to poultry barns.
On 4 and 7 November 2020, an increasing number of dead chickens were reported in two poultry barns in Kagawa Prefecture, Japan. After analysis, influenza A viruses were detected from the dead chickens (Kagawa 1 and Kagawa 2 strains), and NIAH concluded both strains as subtype H5N8. Following the criteria adopted by the World Organization for Animal Health (OIE), the virus was determined as HPAIV.
NIAH decoded the whole-genome sequence of Kagawa 1 and Kagawa 2 strains and the eight gene segments were compared with those from already known influenza A viruses. As a result, all of the gene segments showed a similarity with the H5N8 subtype HPAIV which was prevalent in Europe last winter.
In addition, Kagawa 1 and 2 strains showed high homology with the H5N8 subtype HPAIV which had been isolated from the feces of wild birds in Hokkaido in October 2020 in all eight gene segments. These facts indicate that the recent outbreaks in western Japan were caused by the virus brought into the country by migratory birds.
The deduced amino acid sequence of the virus showed no trace of resistant mutation to neuraminidase or viral RNA polymerase inhibitors. There was also no sign of amino acid mutation to increase the infectivity of the virus to mammals.
NIAH continues to investigate the infectivity of this virus to poultry and the virus excretion.