Isolation And Identification Of Infectious Bursal Disease In Hebei Province

Infectious bursal disease virus (IBDV) is the causative agent of a highly contagious disease in chicken.The outcome of immunization was poorly identified. IBD is one of major contagious diseases that restrain healthy development of the poultry industry in Hebei province which is a heavily concentrated broiler-producing areas.IBD outbreaks were continually observed in Hebei province although a variety of vaccines have been used to prevent IBD.And it has been demonstrated that inactive and attenuated vaccines have been confronted with the threat of variant strains.The appearance of antigenic variants of IBDV could be the reason for those field IBD outbreaks.The strain of IBDV was also obtained through culturing and replicating in SPF embryo several generations and CEF several generations successfully.The character of the virus is 60nm under electron microscope.It is tolerant to aether and chloroform.It can endure pH2.0,but the virulence of the virus reduces a little at 56℃ for 30min.There was no typical symptom in the infected chicken.But lesion of lymphocytes in bursal and spleen were detected under light microscope.The results showed bursal atrophy and splenic edema after infection by IBDV.Lymphocyte necrosis and many neutrophils appeared in the interstitium of lymphoid follicles during anaphase of infection.The index of bursa also becomes smaller after infection.The degree of depletion was correlated with virulence.These characters indicate that IBDVs are of lower virulence.The reverse transcription polymerase chain reaction (RT/PCR) has been previously applied as a sensitive, reproducible and rapid approach for detection and quantification of nucleic acid.In this study,the reverse transcription polymerase chain reaction (RT/PCR) was applied to detect VP2 gene.The target segment of 494bp is amplified successfully.In this study,the coding regions for VP2 of 2 isolates are analysed.The nucleotide and deduced amino acid sequences of the 2 isolates were compared to the reference sequences.According to the strains of the IBDV reported,the phylogenetic tree of the IBDV and the analysis of genetic variation were obtained.The result indicated that the homologous rate with European standard I is 94.5-97.9%,the second one with Cul is 90.3-95.2%.The rate with others is lower,and American standard STC and 002-73 as well.