| The wild aquatic birds are regarded as a major natural reservoir of avian influenza viruses,and they play an important role in the spread of avian influenza viruses,especially migratory birds,which are in close contact with the local poultry or birds in the migration process,and then accelerated the spread of avian influenza virus.In recent years,H5N1 and H5N8 highly pathogenic avian influenza epidemic in the world rapidly and widely spread,which show that the spread of avian influenza virus and its epidemic and wild bird migration is closely related.Therefore,in order to prove the effect of migratory activities of wild birds on the spread of influenza viruses,this study takes the whooper swans as the main research object and monitoring research on wild bird avian influenza viruses in the Central Asian flyway.The preliminary data of the research group shows that Henan,Sanmenxia is the main wintering ground for the whooper swans on the Central Asian flyway,Mongolia and Russia are the breeding ground,and Inner Mongolia is the main stopover site in our country.Therefore,a total of 4792 samples were collected from the main wintering ground and stopover site of Central Asian flyway of whooper swans in china during December 2014 to December 2016 in this study,including 2087 samples of whooper swans,2705 samples of other birds,a total of 103 strains of AIV were isolated,97 strains were isolated from the whooper swans,and only 6 strains were isolated from other species.The results showed that the whooper swans were a susceptible species of avian influenza virus.From the time of virus isolated of different regions,we can speculate the route of transmission of the highly pathogenic H5N1 virus: Henan Sanmenxia-Inner Mongolia – Russia.And it is completely consistent with the spring migration route and the migration time of whooper swans.Phylogenetic analysis showed that eight genes of eight strains H5N1 isolates shared high nucleotide homology with A/rook/Chany/32/2015(H5N1)and A/Black-necked Grebe/Inner Mongolia/Trachea3/2015(H5N1)(more than 98.3% and 98.6%,respectively),and they have a close genetic relationship.The results showed that whooper swans play an important role in the spread of the avian influenza virus.From the time of virus isolated of different regions,we can speculate the route of transmission of the highly pathogenic H5N8 virus: Russia-Inner Mongolia-Henan Sanmenxia.Phylogenetic analysis showed that seven genes(except PA gene)of nine strains H5N8 isolates shared high nucleotide homology with MS/IM/Q3-4/2016(H5N8)isolated from Inner Mongolia and A/common tern /Uvs-Nuur Lake/26/2016(H5N8)(more than 98% and 98.7%,respectively),and they also have a close genetic relationship,PA gene shared the lower nucleotide homology with MS/IM/Q3-4/2016(H5N8)(more than 96.6%),and shared high nucleotide homology with A/common tern /Uvs-Nuur Lake/26/2016(H5N8)(more than 98.9%).At the same time,one tracking whooper swans migrate from Uvs-Nuur Lake of Russia to return to Sanmenxia of Henan in November 2016 and it died in Sanmenxia,identified highly pathogenic H5N8 avian influenza virus by laboratory.We found that the strain shared high nucleotide homology with A/common tern /Uvs-Nuur Lake/26/2016(H5N8)(more than 98.9%)through sequence alignment.Therefore,this study found conclusive evidence that whooper swans can transmit highly pathogenic H5N8 avian influenza virus during long distance migration.Some genes or all genes of all low pathogenic isolated strains in this study shared high nucleotide homology with Mongolia virus strains(more than 98.3%),and they have a close genetic relationship,indicating that the whooper swans play an important role in the spread of avian influenza virus and genes exchange between China and Mongolia.In summary,this study confirmed that the whooper swans are a susceptible species of avian influenza virus,and play an important role in the transmission of avian influenza virus,especially the highly pathogenic avian influenza virus. |
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