鸡传染性支气管炎病毒肾致病株的致弱及免疫研究

用已鉴定的广西鸡传染性支气管炎病毒(IBV)分离株G,C,Z和Q分别通过鸡胚传代进行致弱,在一定代次时分别接种敏感鸡作毒力测定试验.然后用已致弱的毒株在实验室进行攻击保护试验,最后取已致弱而且抗原性良好的毒株在广西各地鸡场进行田间应用试验。结果表明,C株在传至40代时,G,Z和Q株分别传至20代时对鸡的毒性均已大大降低;免疫鸡用标准强毒株(M_(41))攻击,然后用病毒回收的技术来衡量其免疫力,结果各株经免疫两次后均有很好的保护率(60％～100％),均显著优于对照组(P<0.01);致弱株分别在南宁、柳州、容县、岑溪和博自5县市的11个鸡场进行田间试验,试验的鸡有30群共103761羽,试验时分别对疫苗免疫对鸡生产性能的影响、安全性和育成率进行观察和测算,结果表明,作者培育的IBV弱毒苗对鸡是安全的,使用C_(60)或C_(80)和G_(20)株先后两次免疫鸡,对IB有较好预防效果,这些弱毒株有希望成为供生产使用的疫苗。

THE ATTENUATION AND IMMUNIZATION OF NEPHROPATHOGENIC STRAINS OF INFECTIOUS BRONCHITIS VIRUS

The identified strains G, C, Z and Q of infectious bronchitis virus were attenuated by passing in the etnbryonating chicken eggs. At certain passage, the attenuating viruses were inoculated into the susceptive chickens for the examination of virulence. The attenuated viruses were then tested for their immunogenicity, and the good ones were applied in the field. The results demonstrated that after passing 40 passages in the embryonating eggs for strain C and 20 passages for strains G, Z, and Q,the virulence of the attenuated viruses to chickens were very weak} two times' vaccination with the attenuated viruses could provided chickens with a very good protection (80%-90%) against the challenge of virulent strain of IBV (M_(41)), which was significantly higher than that of the unvaccinated control (P<0. 01); the field application of the attenuated viruses in Nanning, Liuzhou and Rong, Cenxi, Bobai County with 103 761 birds of 30 flocks from 11 farms has shown that the vaccinations with strains C_(80)or C_w and G_(20) respectively at 5-day-old and 15-day-old had a better protection (mortality, 4.43%) than the unvaccinated control (mortality, 10. 42%) and the strain D_(41) control (mortality, 9. 98%) (P<0. 01), and the vaccinations were free from side effect. The results of the study demonstrated that the attenuated viruses have a great potential to apply in the poultry industry as the commercial vaccines.