| Mycoplasma Synoviae(MS) is the pathogeny of Avian onfectious Synovitis.It mainly invades the synovial sac and tendon sheath of chicken joints,causing synovitis,tenosynovitis and swelling of joints.It usually arises with Escherichia Coli in clinical practice,and can lead to chest bursitis,airbag inflammation and other respiratory diseases,and makes the disease complicated.It usually leads to decreased production performance in broiler growth,hens laying and breeder breeding,causing huge economic losses.In recent years,it shows a rising trend in our country,while we known little about MS epidemic strains and their genetic variation,which restricts vaccine development prevention of MS in different degrees.This study uses 30 joint fluids to isolate MS strains from suspected MS chickens from Shandong,Hebei,Hubei,Ningxia provinces.Preliminary evidence indicates that the 30 isolates are MS through colony morphology,microscopic morphological characteristics,culture characteristics,erythrocyte adsorption and other tests.The stydy conducts the pathogenicity test of the isolated strains,using MS liquid culture to immune 4-week-old SPF chickens through leg muscle and observing for 21 days.When autopsy,joint synovial sac,keel synovial sac and hock joint synovial sac present typical onfectious features.Identification with 16 S r RNA on isolated strains show that all the isolates are MS.A total of 11 MS strains are obtained,with the isolation rate 36.7%.In this study,11 MS isolates were amplified by PCR using the hemagglutinin vlhA gene primer,after revovering and sequencing amplified products,constructed the vlhA phylogenetic tree and analyzed gene evolution with typical MS strains sequences from Gen Bank.The result shows that the main MS strains in China have high homology and it is very conservative.10 of the 11 isolates are highly homologous and belong to the same branch with isolates from Shandong,Hebei,Hubei,Jiangsu,Anhui,Heilongjiang,Ningxia from 2016～2019.Significantly regional differences with MS isolates from the United States,Australia,Slovenia,India and other regions.Comparing with the current vaccine strains,10 isolates in this research are belong to the same branch with MS Vaccine strains HN01 from JAAS(Register No.CP034544.1),both belong to the typical MS endemic strains in China,which provides an effective reference for the clinical application and selection of vaccines.In addition,the vlhA sequence of HBJZ isolated from Jingzhou,Hubei Province was significantly different from that of the current domestic strains,and belonged to different branchs,This also represents that the current MS epidemic strains in China are shifting to multiple branches,This finding poses a new challenge that whether the current vaccine can effectively block the infection MS strains,and also provides reference information for further research on MS immunology.This study also conducted the MS antibody screening with chicken serum in 17 commercial farms from Shandong,Jiangsu,Hebei,Henan and Anhui provinces.The result shows that the MS antibody positive rate of the 17 commercial chicken farms varies from 20% to 70%,the average MS positive rate is 44.1%.Which shows a high positive rate and low antibody level.It provides reference information for clinical research and control of the disease.?... |
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