Effects Of Waterbirds Migration On Genetic Evolution Of H2 And H4 Subtype Avian Influenza Virus From Wild Birds In Eastern China

Wild birds are a natural reservoir for avian influenza virus.The virus can spread to other wild birds and domestic birds during bird migration.The Bohai Bay and Minjiang Estuary in Fujian Province are important stopover sites located in the East Asian-Australasian Flyway.Every year,a large number of waterbirds rest in Bohai Bay and Minjiang Estuary,which accelerated the the virus spread.To understand the correlation between genetic evolution of avian influenza virus and the migration of waterbirds in Bohai Bay and Minjiang Estuary,the recovery data of water birds including waders,anatidaes and gulls were analyzed.During the spring migration in April 2017 and from April to May in 2018,about 3,000 fecal samples of waterbirds were collected at the Bohai Bay and Minjiang Estuary.The samples were tested and analyzed,8 strains of avian influenza virus were isolated from samples at the Minjiang Estuary in Fujian Province,including 7 H2N6 subtype and 1 H4N6 subtype strain.Three avian influenza viruses were isolated from Bohai Bay samples,including 1 H4N6 subtype,1 H2N7 subtype and 1 H2N8 subtype.The molecular characteristics and genetic evolution of these 11 avian influenza viruses were analyzed,and the relationship between the transmission of avian influenza virus and the migration of wild birds in Bohai Bay and the Minjiang Estuary was explored.The results showed that the HA protein lysis sites of the 11 isolates were consistent with the molecular characteristics of the low pathogenic avian influenza virus,but showed a potential trend of increased virulence.The 8 strains from Fujian had higher homology and were closely related to 897 strains from Hebei,indicating that the virus would spread from Fujian to Bohai bay in spring migration.Hebei 854 and 240 strains were not related to Hebei 879 and Fujian 879 strains.The 8 genes of the virus were homologous with Mongolia,Japan,Korea,Russia and Bangladesh,which indicated that these two strains were recombinant strains,the internal genes spread from other areas to Bohai bay,and there was gene exchange between Eurasia,North America and Australia.The transmission of avian influenza virus in Bohai Bay and Minjiang Estuary in Fujian Province are closely related to the large-scale migration andaggregation of birds,and also may be transmitted between Central Asian Flyway and East Asian-Australasian Flyway.