Isolate,Identification And Antibody Level Detection Of H9 Subtype Avian Influenza Virus Strains In Some Areas Of Shanxi

Avian influenza is an acute infectious disease caused by the avian influenza virus of Orthomyxoviridae,which is mainly divided into highly pathogenic avian influenza and low pathogenic avian influenza.H9N2 subtype is the most widespread low pathogenic avian influenza,which mainly affects the respiratory system and digestive system of birds.It has been popular in our country for more than 20 years,causing great harm.From 2016 to 2018,a total of 700 samples of nasopharynx swabs were collected from poultry in Taiyuan and Jinzhong.94 positive samples were successfully detected by RT-PCR after inoculating chicken embryos and blind transmission for three generations.In addition,15 positive samples were amplified by RT-PCR for HA,Na,M,NS,NP,PA,PB1 and PB2,and sequenced for sequence correlation analysis.The results showed that the 15 strains had great variation compared with some classical vaccine strains such as F98 and sd696.In addition,the 226th-228 th amino acid site in the left arm of the HA receptor binding site of the 15 strains mutated to LMG,which made the virus have the ability to bind sialic acid receptor ?-2,6-Gal,thus it has the risk of infection to human beings.In order to further understand the prevention and control of avian influenza in Shanxi Province,1548 serum and yolk samples were collected from Taiyuan and Xinzhou in 2019,and the antibody level of H9 subtype AIV was detected by HI test.It is found that the immunization situation in all regions is up to the standard,but in some regions there are more than 25% suspected infection rates.It is suspected that some vaccines have not been able to fully protect the body from the current HIV infection in Shanxi Province.In conclusion,the H9 subtype of AIV in Shanxi Province has changed to a large extent under the long-term pressure of immune selection,and the protection of some classical vaccines to the body has declined.It is necessary to continuously monitor the prevalence of AIV and understand the variation of AIV,so as to avoid the large-scale epidemic of H9 subtype avian influenza in Shanxi Province and provide theoretical basis for the selection and use of vaccine.