Characterization of a non-pathogenic H5N1 influenza virus isolated from a migratory duck flying from Siberia in Hokkaido, Japan, in October 2009

Naoki Yamamoto,Masatoshi Okamatsu,Masayuki Motoshima,Kosuke Soda,Yoshihiro Sakoda,Hiroshi Kida,Fumi Yoshino

doi:10.1186/1743-422x-8-65

Naoki Yamamoto, Masatoshi Okamatsu + Show 5 more

Open Access

https://doi.org/10.1186/1743-422x-8-65

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Abstract

BackgroundInfection with H5N1 highly pathogenic avian influenza viruses (HPAIVs) of domestic poultry and wild birds has spread to more than 60 countries in Eurasia and Africa. It is concerned that HPAIVs may be perpetuated in the lakes in Siberia where migratory water birds nest in summer. To monitor whether HPAIVs circulate in migratory water birds, intensive surveillance of avian influenza has been performed in Mongolia and Japan in autumn each year. Until 2008, there had not been any H5N1 viruses isolated from migratory water birds that flew from their nesting lakes in Siberia. In autumn 2009, A/mallard/Hokkaido/24/09 (H5N1) (Mal/Hok/24/09) was isolated from a fecal sample of a mallard (Anas platyrhynchos) that flew from Siberia to Hokkaido, Japan. The isolate was assessed for pathogenicity in chickens, domestic ducks, and quails and analyzed antigenically and phylogenetically.ResultsNo clinical signs were observed in chickens inoculated intravenously with Mal/Hok/24/09 (H5N1). There was no viral replication in chickens inoculated intranasally with the isolate. None of the domestic ducks and quails inoculated intranasally with the isolate showed any clinical signs. There were no multiple basic amino acid residues at the cleavage site of the hemagglutinin (HA) of the isolate. Each gene of Mal/Hok/24/09 (H5N1) is phylogenetically closely related to that of influenza viruses isolated from migratory water birds that flew from their nesting lakes in autumn. Additionally, the antigenicity of the HA of the isolate was similar to that of the viruses isolated from migratory water birds in Hokkaido that flew from their northern territory in autumn and different from those of HPAIVs isolated from birds found dead in China, Mongolia, and Japan on the way back to their northern territory in spring.ConclusionMal/Hok/24/09 (H5N1) is a non-pathogenic avian influenza virus for chickens, domestic ducks, and quails, and is antigenically and genetically distinct from the H5N1 HPAIVs prevailing in birds in Eurasia and Africa. H5 viruses with the HA gene of HPAIV had not been isolated from migratory water birds in the surveillance until 2009, indicating that H5N1 HPAIVs had not become dominant in their nesting lakes in Siberia until 2009.

Highlights

Infection with H5N1 highly pathogenic avian influenza viruses (HPAIVs) of domestic poultry and wild birds has spread to more than 60 countries in Eurasia and Africa
The virus was not recovered from the tracheal and cloacal swabs and tissues of chickens intranasally inoculated with Mal/Hok/24/09 (H5N1) on three dpi, and there were no antibodies to H5N1 virus detected by enzyme-linked immunosorbent assay (ELISA) on 14 dpi (Table 3), indicating that chickens were not infected with the isolate
In the surveillance studies of avian influenza in autumn since 1996, H5 viruses with the HA gene of A/goose/Guangdong/1/96 (H5N1) had not been isolated from migratory water birds that flew from Siberia to Japan and Mongolia (Figure 1) indicating that H5N1 HPAIVs had not become dominant in their nesting lakes in Siberia until 2009

Summary

Introduction

Infection with H5N1 highly pathogenic avian influenza viruses (HPAIVs) of domestic poultry and wild birds has spread to more than 60 countries in Eurasia and Africa. It is concerned that HPAIVs may be perpetuated in the lakes in Siberia where migratory water birds nest in summer. Non-pathogenic avian influenza viruses (NPAIVs) circulating in waterfowl transmit to terrestrial birds such as quails and turkeys through domestic water birds such as ducks and geese in live bird markets. After 2005, H5N1 HPAIVs have been isolated from dead migratory water birds in China, Mongolia, Russia, and Japan on the way back to their nesting lakes in Siberia in spring [4,5,6,7,8]. It is a serious concern that HPAIVs may be perpetuated in the lakes where migratory water birds nest in summer, and that those migratory water birds may bring HPAIVs to the south in autumn

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