Phylogenetic Analysis On A Wild Duck (Common Teal)-origined H5N2 Subtype Avian Influenza Virus Isolate

Influenza virus family can be divided into type A, B and C. Influenza A viruses are the most widely spread and mutative viruses of these types. Avian Influenza (AI) is caused by Influenza A virus and can be transmitted and infected through the respiratory tract, gastrointestinal tract, and many other ways. According to the pathogenicity, Avian Influenza Virues are divided into highly pathogenic, low pathogenic and non-pathogenic strains.The viruses are further subtype-ed according to the different combinations of HA (H1-H16) and NA (N1-N9). Low pathogenic isolates can mutate into highly pathogenic isolates. Low pathogenic H5N2 avian influenza virus could mutate to highly pathogenic H5N1 avian influenza virus. Low pathogenic H5N2 isolate can also shift itself to be highly pathogenic.Wild birds especially waterfowls are the natural hosts for Avian Influenza Virus. Fecal-oral transmission via contaminated water is its main mechanism of transmission. An avian influenza virus strain from wintering Common Teal (Anas crecca) in Shanghai, 2007 was identified as H5N2 subtype AIV (A/Common Teal/Shanghai/1F/2007).The HA cleavage site amino acid sequence of our strain is REARGLF, according to which the strain is recognized as a low pathogenic avian influenza virus. Phylogenetic analysis was based on the HA,NA,M,NS,NP sequences of this strain. The Phylogenetic trees of the strain's genes were constructed with H5N2 strains selected from GenBank. Our results showed that HA gene had the highest homology with the low pathogenic avian influenza strain aquatic bird/Korea/w191/2007(H5N2). NA gene had the highest homology with the low pathogenic avian influenza strain aquatic bird/Korea/w193/2007(H5N2). M gene had the highest homology with the low pathogenic avian influenza strain aquatic bird/Korea/wl93/2007(H5N2). NP gene had the highest homology with the low pathogenic avian influenza strain aquatic bird/Korea/w221/2007(H5N2). NS gene had the highest homology with the low pathogenic avian influenza strain aquatic bird/Korea/wl32/2006(H5N2).The genes of our strains (A/Common Teal/Shanghai/1F/2007) showing the highest homologies with the low pathogenic strains born by water birds in Korea indicated that the AIV circulated in water birds in East Asia probably shares same gene pool of viruses via annual migration.