Avian Influenza Surveillance Of Migratory Waterfowls In Freshwater Lakes In Hubei Province And Characterization Of Two H7N7Influenza Viruses Isolated From Waterfowls

In recent years, frequent outbreaks of avian influenza virus of multiple subtypeshas seriously affected the poultry industry and human health. Wild birds areconsidered natural reservoirs of avian influenza virus for the isolation of manysubtypes of avian influenza virus in birds. Birds migration around the world inautumn and winter provides great chances for recombination and reassortment ofinfluenza virus. Among which, Anseriforms and Charadriiformes play an importantrole in the spread of avian influenza virus. Anseriforms comprises about150livingspecies including ducks, geese, swans and screamers. Charadriiformes includes about350species containing waders, gulls, terns and so on. These birds distributed verywidely across the globe and has members in all parts of the world with migratoryhabits. Surveillance and control of wild bird avian influenza virus helps to understandthe geographical and seasonal distribution of AIV, and thus a comprehensiveunderstanding to the molecular characterization and evolution of the virus andbenefits a lot.Since Nov2013to Mar2014, we conducted the research and1699of fresh birdsfeces samples were collected in three important lakes in Hubei province.11isolates ofAIV including three HA subtypes of H5,H6and H7were separated, which shed incormorant and bean goose without significant illness symptoms. The number of birdsare vary geographically and seasonally.Evolutionary analysis of different HA segment showed that, three H5N6wereclade2.3.4subtype,which is a molecular characteristic of highly pathogenic of AIVs.Five H6subtypes were Eurasian linage and share a same ancestor. The data has alsoshown that reassortment has occurred in all of the viral subtypes isolated, and all8genes in the predominant H7N7virus lineage have evolved to be phylogeneticallydistinct.HAI experiment suggested that two H7N7virus can be neutralized by H7N9antibodies, and H7N7infection mice antiserum can neutralize H7N9virus at a HAItiters from20to40. Two strains of Influenza virus can be well replicated in MDCKand A549cell lines, but viral persistence vary according to different temperaturesand pH. Analysis of virulence relevant site in internal proteins revealed two strains ofH7N7virus mutated in several sites, but analysis of HA cleavage site show that twostrains are low pathogenic, and sensitive both to neuraminidase inhibition and ionchannel inhibition, animal experiments in BALB/c mice also confirmed that theviruses are low pathogenic.In this paper,we conducted avian influenza surveillance of migratory waterfowlsin freshwater lakes in Hubei Province,to get a better understanding of ecologicaldistribution,prevaillance,and characterization of avian influenza virus to provideinfluenza surveillance and monitoring data.