A Study Of Surveillance Of AIV H5N6 From Wild Ducks In Ningxia Province And Its Pathogenicity In Mouse

Before 1996,only highly pathogenic avian influenza virus(HPAIV)could infect humans by infecting intermediate hosts.In 1996,H5N1 subtype HPAIV(Gs/GD lineage)was found in domestic geese in Guangdong,China.Unlike previous outbreaks of H5 subtype highly pathogenic avian influenza(HPAI),this subtype virus can directly cross the host barrier Infecting wild birds and humen and causing the death of the host has now spread to more than 80 countries in Asia,Europe,Africa and North America.In April 2014,the first case of human infection with H5N6 subtype AIV occurred in Sichuan Province.The patient was died of shortness of breath and severe pneumonia.H5N6 subtype AIV gradually replaced H5N1 subtype AIV as the main subtype of poultry infection in southern China.Wild birds are the natural host of AIV,and 16 HA subtypes and 9 NA subtypes can be isolated in wild birds.Wild birds,especially migratory birds,can carry viruses to migrate,spread the virus to different regions,and even spread across borders and intercontinental.At the same time,during the migration,it will intermingle with the poultry or wild birds in the habitat,which is conducive to the recombination of the AIV gene,thereby accelerating the spread and mutation of AIV,and enriching the genetic diversity of AIV.Therefore,genetic evolution analysis of wild bird-derived H5N6 subtype AIV,to grasp the genetic evolution of the virus;through the mouse infectivity test,to assess the virus's ability to infect mammals and pathogenicity,has important public health significance.Through long-term AIV surveillance of wild birds in Ningxia,a total of 22 strains of H5N6 subtype AIVs were isolated from wild birds in Ningxia in the winter of 2015 and 2017.The results of genetic evolution analysis was shewed that 22 strains of H5N6 subtype AIV can be divided into 6 genotypes,5 genotypes are HPAIV,1 genotype is LPAIV,and H5N6 of 3 HPAIV genotypes are highly homologous to human H5N6.All five strains of H5N6 subtype HPAIV had key amino acid mutations related to enhancing the pathogenicity of the virus to mammals.In this study,from the five genotypes of HPAIV,one H5N6 isolate was selected as a representative strain for mouse experiments.The results showed that the virus could directly infect mice without adaptation and showed low or moderate pathogenicity.This indicates that the H5N6 subtype HPAIV of Ningxia wild bird has the ability to infect mammals,and may spread with wild birds' long-distance migration,and has the potential to infect human.Therefore,strengthening the surveillance of the AIV status of wild birds and the pathogenicity evaluation of viruses on mammals can provide evidence support for early warning and prevention of poultry influenza,and provide important early warning instructions for the occurrence of human outbreak.