Wild Bird Avian Influenza Surveillance And Mammals Cross-species Transmission Capacity Evaluation

Avian Influenza is a variety infection disease syndrome of poultry and wild birds caused by influenza A virus. Avian influenza virus can be divided into highly pathogenic and low pathogenic avian influenza virus according to its pathogenic in avian. In recent years, avian influenza virus especially low pathogenic avian influenza virus frequent crossed the species barrier, directly infection of humans or other mammals, even causing death event in human. The role of wild birds as reservoir host in the spread of the virus has been highly gained concerns. H5N1subtype avian influenza has spread across14countries and more than40areas along with migratory wild birds in less than two years. At least two genes of human infection H7N9subtype avian influenza virus come from wild bird virus variation. The genes of caused human infection H10N8avian influenza virus in Jiangxi are also originated from wild birds. Avian influenza especially highly pathogenic avian influenza has seriously endangered to human beings, and has the potential to break through the species barrier and caused next influenza pandemic. On the one hand, the developed countries have the wild bird influenza monitoring included in the normal monitoring disease surveillance. Chinese forestry bureau have carried out active surveillance since2008. However, the monitoring work of avian influenza in wild birds in China is relatively backward because of the sampling is extremely difficult from wild bird; especially the national investment is relatively limited. For example, before the event H7N9infection in2013, precursor virus have been detected in the wild duck by our neighboring countries such as Japan and South Korea, but our traceability was not effective because of lack monitoring related strains. On the other hand, the phenomenon of H5, H6, H7, H9, H10subtype avian viruses infection human suggested that more subtype of avian influenza virus would pose a threat to human health. Therefore, it is necessary to in-depth understanding of the influenza virus distribution among wild birds and mammalian cross species transmission, not only for deepen our understanding of the influenza virus, but has an important significance to avian influenza prevention and control.In this study,15152samples were collected from48regions of14provinces, and then isolation and identification of influenza virus were performed.57strains of avian influenza virus were obtained from wild birds in this survey, the influenza virus positive rate is about0.38%, and the rate of autumn sample is higher than its in spring. Swab sample isolation rate is about0.42%, feces (environment) sample isolation rate is0.40%, and tissue sample isolation rate is0.18%.57strains of virus containing8HA and7NA subtypes, H3, H4subtype is the predominant strains, but highly pathogenic avian influenza H5subtype is also distributed to a wide range in wild birds, accounting for17.5%of the overall isolation of virus, the situation of prevention and control of this disease still grim. In order to understand the relationship between the origin of these strains and the domestic epidemic strains (including human, porcine epidemic strain),30strains was selected for study by whole genome sequencing. Phylogenetic analysis of HA gene showed that, except for the H3subtype with host specificity in avian; the other subtypes were originated from bird, pig or poultry, or all three gene recombination. NA gene evolution was more complex, but no synergistic or consistency with HA in relation to the evolution. Compared to the external gene, the evolutionary relationship of genes (PB2, PB1, PA, NP, M, and NS) was more complex, the phenomenon of gene segments recombination of influenza virus from bird, pig, human host was also observed. The results indicated that wild bird is a reservoir host and natural genes bank of influenza virus genes, providing gene segments for different subtypes and different hosts. In addition, there is need to further strengthen the monitoring of migratory birds because of first isolation H13N6and H5N8virus in wild birds.In order to understand the pathogenicity of these viruses to mammals, mice were selected as model to evaluate the characterization of infection and pathogenic of28representative virus strains isolated from wild birds. The selected viruses can be replicated in mouse lungs, nasal turbinates, but the virus titer different, the H5N8subtype is the highest, up to105.7EID50/ml. The H3N2, H5N1, H5N8, H4N6, H7, H9N2subtype strains can cause mice death, the mortality of H5N8reached up to100%, the rest of the H3and H6subtypes of the virus can make mice infected without clinical special features. These results showed that the sourced wild bird virus may directly infect humans without adaption. The receptor binding property and horizontal transmission between guinea pigs were analyzed to evaluate transmission in mammals. Receptor binding assay showed that the H3subtype virus has SA a-2,6Gal (human-like influenza virus receptor) binding property, H7, H9subtypes has SA α-2,6Gal binding property in some degree. H3and H9subtypes strains were selected for contacted transmission in guinea pigs, the S89(H3N2), ZH47(H3N3) and JL-2(H9N2) can transmit in guinea pigs, in which S89(H3N2) was the highest (2/3). The recombinant rS89strains were constructed by reverse genetics technology and found that rS89-HA-L2741can influence the S89virus SA α-2,6Gal receptor binding characteristics. These results showed that except the series of sites have been found; other sites receptor binding may also affect the recognition ability of virus receptor.We established viral metagenomic to analyze the pathogen of wild birds, wild domestic mammalian. The method is universal for different type samples, such as environment, tissue, or swab samples. This method was first used to study viruses and distribution of wild bird, and detect a variety of virus (goose circovirus, pheasant herpes virus, duck hepatitis B virus, crane, hepatitis B virus, avian influenza virus etc.). Porcine epidemic diarrhea virus and porcine novel kobuvirus were found in outbreak of pig death. Most of Hantaviruses carried by animal hosts in Jilin Province were Seoul viruses, of which the genetics showed a diversity. These results showed that the method is important to new or unknown viral pathogens.