| The H9N2 subtype avian influenza which occured frequently all over our country for more than twenty years from 1992,caused a huge economic losses to the poultry breeding industry.And now it is still a serious question to control the disease.The effect of existing vaccine for H9N2 subtype avian influenza is unsteady because of the constant mutation and recombination of H9N2 virus.What's more,the AIVs were overcoming the barrier of different races continuously and have become a serious threat to the safety of human life.Continuous monitor of antibody levels and flu of avian influenza,make a great significance to develop new vaccine and capture the new types of strains which was always menacing the public health and safety of human life.Recent years,we collected the serum and swab samples to monitor the trends of molecular evolution and mutation of H9N2 AIVs during July 2015 to 2016 February from eight regions in Jiangsu Province which covered 64 live avian markets and poultry farms.The dynamic changes of serum antibody levels was detect and monitor by serological methods.I separated and preliminary identificated the H9N2 AIVs,then sequenced the whole genome of positive stains,I analyzed and amino the acid sequence of the gene of H9N2 AIVs by biological software DNAstars and Magalign,and then drawwd a phylogenetic trees with soft MEGA.2869 serum and 2966 swabsin samples were collected during the study,including 1933 serum and 1954 swab samples from chicken;405 serum and 432 swab samples from ducks;531 serum samples and equal amunts of swab samples from geese.Among them,2256 serum samples were detected and 1346 were qualified with a larger dispersion,the positive percentage was 59.66 and 10.34 percent was below the minimum standards of the Ministry of Agriculture.21.23%of samples were detected with no antibodies for H9N2 AIVs.Results of different poultries shows that the positive rate of chicken was highest which accounting for 71.28%,and then the geese 57.75%,the ducks were last for 10.68%.Results of different regions shows that the positive rate of the south of Jiangsu Province,the north of Jiangsu Province and the central region were respective 64.87%,50.22%and 58.33%.On the other hand,the whole monitoring results show that antibody levels fluctuate greatly over time,the highest antibody levels is February 2016,was 71.31%and the lowest is July 2015,47.18%.Results of different scale farming shows the breeding poultry field occupied the top,then the farmers,and the live avian markets,last is the backyard farmers,while,there is a big security risk for the positive rate of antibody of live poultry markets and backyard farmers was only 46.84%and 16.07%.Three H9N2 AIVs were isolated and the complete genome were sequenced,homology analysis of gene sequence and the amino acid sequence showes,all of the three viruses have a significant feature of low pathogenic avian influenza molecule,and the HA gene belong to the BJ/1/94 branch of Y280 subline;NA genes belong to SH/F/98 subline;NP,NS,PB1 are all come from SH/F/98 subline,while the MP,PA,PB2 gene belongs to G1 subfamily.Genetic analysis shows the evolution of the three virus,only the PB2 gene mutation produced a new genetype;and the H9N2 subtype AIVs evolution related with time,without the distribution of geographic location. |
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