广西某鸡群呼吸道综合征的病原学分析

The etiological analysis on one case of respiratory syndrome of chickens in Guangxi

本研究对临床上患呼吸道感染的病鸡进行病原检测,分离到1株传染性法氏囊病病毒(infectious bursal disease virus,IBDV)和1株传染性支气管炎病毒(infectious bronchitis virus,IBV),此外还从病鸡肝脏等组织中分离到金黄色葡萄球菌和大肠杆菌。对IBDV分离株NN160401的VP1-b、v VP2基因以及IBV分离株GX160421的S1基因分别进行扩增、测序以及序列的相似性比较和遗传进化树分析。结果发现,分离株NN160401为基因重排毒株,其VP1-b与HLJ-0504株的序列相似,v VP2则具有IBDV超强毒株特征;分离株GX160421的S1基因序列与广西分离株亲缘关系较近,属于近年报道的New-typeⅡ,但与其他参考株及疫苗株H120的核苷酸相似性仅为58.8%~67.2%。综合分析表明,该病鸡群为早期感染IBDV造成了机体的免疫抑制,后来继发IBV的感染并伴发了细菌感染。

A diagnostic study was carried out in a clinical case of chicken flock that experienced respiratory infections. One strain of infectious bursal disease virus（ IBDV） named NN160401 and an infectious bronchitis virus（ IBV） strain named GX160421 were isolated from chickens. Also,Staphylococcus aureus and Escherichia coli were also isolated from the liver. Polymerase chain reaction（ PCR） was performed to detect the VP1-b and v VP2 genes for IBDV and the S1 gene for IBV,and the sequencing comparison and phylogenetic trees of the genes were analyzed. The results showed that NN160401 was a reassortant strain,as its VP1-b was shown to be in the HLJ-0504-like cluster while the v VP2 was genetically close to that of the very virulent IBDV（ vv IBDV） isolates. The nucleotide sequences of S1 gene of GX160421 was genetically close to the Guangxi isolates and belonged to the recently reported New-typeⅡ cluster,but the sequence similarities with the reference strains were only 58. 8% to 67. 2%. In summary,the case of respiratory syndrome was determined to be caused by IBV as the secondary infection to the early immunosuppressive infection of IBDV,accompanied with the bacterial infections.