HA And NA Genes Phylogenic Analysis Of AIV Isolates From Wild Birds And The Distribution/Transmission Pattern Of AIV In Wild Birds

Avian influenza(AI),caused by the influenza virus type"A",can affect domestic poultry,pet birds and wild birds.It is severely danger to public health and wild bird populations.Wild birds are approved as natural hosts of AIV.And avian influenza viruses are cycling in wild birds.It's necessary to investigate and analysize the prevalence,distribution pattern of AIV and the role of migrant birds for transmission of AIV between wild and captive and between different species.The thesis includes three parts:The first part:Surface gene phylogenic analysis of AIV isolated from wild birds inhabit in Heilongjiang areaThe samples were collected from agonal lesser kestrel submitted by Harbin forestry bureau 2006,and others from wild birds in "Sanjiang" national natural reserve in Heilongjiang province 2006.Cloacal swabs were taken from wild birds.The samples were found to be positive for influenza virus.Culturing and subsequent subtyping of viruses from these samples revealed three different haemagglutinin(HA)/neuraminidase(NA) subtypes(H5N1,H5N2,H3NS) by National Influenza Reference Laboratory.The N-J phylogenetic tree structured and analyzed using software-MEGA4,showed that HA gene of A/Lesser Kestrel/Harbin/194/2007 harbored a series of basic amino acids(-RRRKKR-) at HA cleavage site similar to the sequences characteristic of HPAIV,phylogenic analysis suggested that the HA gene of A/Lesser Kestrel/Harbin/194/2007 was originated from poultry of H5N1 in southern China.The NA gene have evolved to a separate clade of which many viruses from Southeast coast of China and southeast Asia after 2005.HA cleavage site of A/Garganey/SJ/160/06 was similar to the sequences characteristic of LPAIV,the HA gene have evolved to a first clade of which 2 viruses from Jiangxi and Japan formed a closer clade,a farther clade with those from Europe and America.The NA phylogenic tree was similar to the HA,but A/Garganey/SJ/160/06 is in clade 1,of which the viruses from Jiangxi and part of Europe and America formed a closer clade, a farther clade with those from Japan.The HA of H3N8 cleavage sites of 2 viruses from Sanjiang were similar to the sequences characteristic of LPAIV.The HA genes of H3N8 from Sanjiang were grouped together and highly similarity,belong to Eurasia lineage.The NA gene of A/Mallard/SanJiang/167/2006(H3N8) has evolved to second clade belong to North American lineage,of which Aquatic bird/Korea/JN-1/2005 formed a closer clade.The NA gene of Mallard/SanJiang/167/2006 was likely originated from aguatic bird.The NA gene of A/Mallard/SanJiang/98/2006 was in the clade 3,belongs to Eurasia lineage and was originate from poultry.The second part:Analysis of distribution pattern of AIV in wild birdsThe analysis showed that avian influenza viruses were isolated or the samples were found to be positive for influenza virus using serologic identification from at least 130 species of global wild birds.This demonstrates that wild birds play a role in the perpetuation of LPAIV;but the role of wild birds as the hosts of HPAIV is not very clear.LP virus might variate HP during cycling between domestic poultry and wild bird.In addition,not only migrant but also resident birds can infect HP subtype H5N1 virus.The paper discussed some questions base on the research data of AIV,including the prevalence of each subtype of AIV in global wild birds,distributing pattern of AW in wild birds,influenza viruses in ducks,the migratory birds and AIV transmission,seasonal characteristic of AIV infect wild birds and the role of natural environment reservoirs in the transmission of influenza viruses;so as to understand much about AIV in wild birds.The third part:Analysis the role of wild birds for long-distance transmission of HPAIV H5N1To identify whether the wild birds can play an role in highly pathogenic avian influenza(HPAI) virus H5N1 spread across different countries or even different states,the following four related research progresses included wild birds asymptomatic infected H5N1,HPAI outbreaks in wild birds, the exchanges of AW genes between north America and Eurasia,and the ecologic immunology study of migratory birds were reviewed in this paper.Based on the analysis of the reviews above,we find that:Firstly,the related studies data is few that can be used to prove wild birds can infect H5N1 but don't show any symptoms,and no evidence from wild bird HPAI outbreaks can support they had spreaded the H5N1 over long distance on seasonal migration routes.But the migratory birds can be infected and may be involved in local spread of the highly pathogenic H5N1 virus is possible. Secondly,while influenza viruses do exchange between the two hemispheres,but it is a rare occurrence,this also can help to prove that the possibility of wild birds spread H5N1 along with theirs migratory routs for a long distance at least from Eurasia to North America is so limit.Thirdly, the obtained study results from ecological immunity of wild birds,mainly the more understanding about the special condition on physical and immune system of wild birds when migratory,cannot support they can still spread the H5N1 for long distance effectively after they infected by HPAI H5N1 virus.In conclution,wild birds could spread the highly pathogenic H5N1 virus to domestic avian,other wild birds even human beings by local movement(or relay race mode).