| Infectious bursal disease virus(IBDV), the causative agent of infectious bursal disease(IBD), causes immunosuppression in young chickens by destroying the precursors of B lymphocytes in the bursa of Fabricius. In 1957, the disease first broke out in broilers in Gumboro, Telahua state, America. In the 1980s, the variation strain of IBDV was fiest appeared in America. Acute IBD caused by very virulent infectious bursal disease virus(wIBDV) was first reported in Europe at the end of 1980s. The acute form of the disease were then transmitted to Japan in the early 1990s, and then rapidly spreaded all over Asia and other major parts of the world. The IBDV has beeen the cause of significant economic losses in poltry industry for a long time. This research studied three aspects: pathogenicity of IBDV, multiplication of IBDV in SPF chickens and compare of the hypervariable region of VP2 gene.The following is the main contents of this reseach:1. The pathogenicity experiments of SD strain of primary bursal virus on SPF chickens: The SD strain of IBDV was isolated from chickens infected by IBDV naturally during 1991 -2004 in Shandong Province. 160 SPF chickens were divided into 8 groups. 7 groups were infected 7 Shandong strains of IBDV by dripping nose and eyes. The last one is the comparison group of the blank. The results showed that all the chickens showed a series of clinical symptoms and the pathogenicity of different strains were similar. Mortality of 7 strains on SPF chickens varied 35% to 50%, it's higher. It showed that SD strains of IBDV epidemic in Shandong is better virulent virus in recent ten years.2. The study of infecting process of IBDV in SPF chickens: In order to study the infecting process of IBDV in SPF chickens ,we triturated bursaltissue, then infected the SPF chickens by dropping eyes and nose.From 2 to 9 days since infection, we detected IBDV in 9 kinds tissues (bursa, spleen, thymus, kidney, liver, amygdalae, lung, heart, faces)by rapid diagnosis strips of immune colloidal and AGP. The result showed that quantity of IBDV in bursal tissue was largest and the time was longest. The second was spleen. The heart was smallest and shortest. The IBDV existed only twe days in the heart. Detecting IBDV in 9 tissues in turn: the first is bursa ,spleen and faces,the second is thymus and amygdalae. The last is kidney,lung,liver and heart. The quantity of IBDV in all tissues reach the peak on sixth day. 3. Cloning and Sequence Analysis of the hypervariable region of VP2 Gene of Infectious Bursal Disease Virus isolated from Shandong in 1991-2004: In order to study the change of high variable region of VP2 gene of Shandong strains of infectious burial disease virus in 1991 to 2004. through RT-PCR, high variable region of VP2 gene of infectious burial disease virus from Shandong were amplified and cloned, then it's nucleotide sequence of VP2 were determined, analyzed and compared. The result showed that the nucleotide sequence of 7 strains of IBDV isolated from Shandong were same. The the hypervariable region of VP2 gene of SD compared with other nine strains (GX8/99, SH, HZ, HK46, F9811,Nigeria,Variant E,CJ801,D78). The homology of the nucleotide sequences of the hypervariable region of VP2 gene of SD with wIBDV is from 96.42% to 97.76%,with vIBDV is 92.39 %,with variant strain is 92.17%,with vaccinal strain is 92.84%. the homology of amino acid SD with vvIBDV is from 97.99% to 100%, with vIBDV is 94.63%, with variant strain is 91.95%, with vaccinal strain is 93.29%. The phylogenetic tree analysis confirm that SD strains is most closely related with wIBDV and distant with vaccine strain and virulent strain. |
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