| Avian influenza(AI)is an avian infectious disease caused by avian influenza viruses(AIVs),which can be classified into two pathotypes based on pathogenicity,named as highly pathogenic AI(HPAI)and lowly pathogenic AI(LPAI),which lead not only huge economic losses to poultry industry,but also great potential threat to human health.Especially,H9N2 AIVs were not only popular in the world,but also the donors of the internal gene of other AIVs.Therefore,H9N2 AIVs were highly concerned by influenza researchers.Vaccine immunization is still one of the most effective ways for prevention and control of AI in China at present.Reasonable immunization program is the key to vaccine effect,and antibody detection can help us to understand the immune situation.On the other hand,the analysis of the current epidemic strains will help us to understand the matched-degree bewteen vaccine and popular strains.1.monitoring of Avian Flu Vaccine in Longzhu Chicken Farm of Jingjiang CityA group of laying hens were immunized according to the immunization program of the chicken farm.Blood samples were collected every month to detect the antibody titer of vaccine.The results showed that the maternal antibody against H5 subtype(Re-6,Re-7,and Re-8),H7 subtype,and H9 subtype AIV were 8.0±1.78 log2,6.28±1.68 log2,8.34 ±1.10 log2,0 log2,and 8.36 ±1.85 log2,respectively.After inoculation with various vaccines,antibody titers against H5 subtype strains began to rise and reach to 6 log2.Antibody levels against H7 subtype strains rose rapidly and were consistently greater than 6 log2 during the entire feeding period.For the H9 subtype strain,a higher level of antibody was produced at 30 days after immunization and was maintained for 2 months,however,the antibody titer began to decline,after dropped to 3.5 log2,the antibody was suddenly increased at late period,suggesting that the poultry might be infected by wild-type strains.During the monitoring process,the discrete values of the antibody titers were smaller fluctuation,indicating that the quality of the vaccines was good,the process of immunization was more standardized and reasonable,and the level of antibodies was relatively stable.2.the whole gene sequence analysis of five H9 subtype avian influenza virusesFive strains of H9 subtype AIV from 22 clinical samples were isolated and identified by chicken embryo inoculation,serological test,and RT-PCR.The whole gene sequence of five H9N2 AIVs were determined by.gene sequencing analysis from single infection sample.Phylogenetic analysis of HA genes indicated that the five H9 AIVs belonged to the Y280-like,which were the dominant strains in East China with 295 potential glycosylation sites.NA genes were genetically located in the Dk/HK/Y280/97-like,and evolutionary distance was close to the classic vaccine strain Ck/SH/F/98 from East China,especially,all isolates lacked the NIT glycosylation site at position 61 because of deleting three amino acid residues TEI at positions 63-65.PB1,PA,NP,and NS were still classified in Ck/SH/F/98-like,while PB2 and M genes from Qa/HK/G1/97-like.In short,the overall situation of the genes was not variable. |
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