Isolation And Identification Of Avian Influenza Viruses From Wild Birds Of Eastern China In 2014

Avian influenza virus(AIV) belongs to Paramyxoviridae, which is consisted with eight segments of negative-standed RNA. Wild birds as the nature reservoir of AIVs play an important role in the transmission, infection and reassortment of AIVs. The surveillance and characterization of AIVs circulating in the wild birds not only illustrate better the epidemiology of AIVs in their natural hosts but also provide authentic prediction of the outbreak of influenza in domestic poultry and human. In our study, a total number of 8760 samples including swabs, tissues and feces were taken from wild birds in eastern China, and 29 strains of AIVs were isolated from these samples, which included H4N6, H5N1, H5N6, H5N8, H9N2, H9N7, H13N6, H13N8 subtypes. To find out the biology characterization of these AIVs from wild bird, the sequence analysis, pathogenicity and transmissibility experiments for these isolates were performed.The sequence analysis of the H5 subtype strains indicates that the H5N1 isolates are classified into the clade of 2.3.2.1, however, the H5N6 and H5N8 isolates fall into the novel clade of 2.3.4.4. H13 subtype isolates are reassortant virus reasserting among Eurasian and north American lineage. In the pathogenicity evaluation experiments, we found that H5N1(I192) virus appears high virulence to mouse model with changing of body weight and causing death in mice, while all the isolates of H4N6, H9N7, H13N8 from wild birds don’t show virulence in mice. The transmissibility studies show that, H5N1(I192)isolates have obtained the limit ability of contact transmission between guinea pigs. The above results suggested that, H5 have acquired the potential ability to threat to human health; and the H13 subtype AIVs circulating in wild waterfowl may not obtain the ability of crossing the species barrier to infect terrestrial bird.To understand the sensitivity of different HA subtype AIVs to erythrocyte of different species, three types of red blood cell(RBC) from turkey, guinea pig, and chicken were used to hemagglutination(HA) test of H1, H3, H4, H5, H6, H7, H9, H13 subtype AIVs. HA test data show that turkey and guinea pig RBCs have higher sensitivity to above viruses than chicken RBCs. The results demonstrated the turkey and guinea pig RBCs should be used for AIVs HA test in virus isolation.