免疫鸡群感染新城疫强毒后群体带毒情况和对生产指标的影响

THE CONDITIONS OF CHICKEN FLOCK SHEDDING VIRULENT NEWCASTLE DISEASE VIRUS AND EGG PRODUCTION IN AN INFECTED IMMUNE CHICKEN FLOCK

应用新城疫病毒单抗ＰＥＧ夹心ＥＬＩＳＡ试剂盒对一新城疫强毒感染鸡群连续监测，检测泄殖腔拭子带毒情况和ＨＩ抗体效价，结果在鸡群发病后３０７ｄ仍可以测出强毒。且随着时间的推移和鸡群ＨＩ抗体水平的下降，强毒感染率呈上升趋势，表明免疫鸡群感染新城疫强毒后，强毒可在群内循环传播和长期维持。采用疫苗免疫把强毒感染率控制在一定水平而不致暴发新城疫，则鸡群可以保持较好的生产性能。而当强毒感染率上升较大时，则生产性能下降明显，死淘率也上升。

A polygethylene glycol(PEG) mediated sandwich ELISA utilizing monoclonal antibodies(Mabs) against Newcastle Disease Virus(NDV) was used to detect viral antigen of virulent NDV(VNDV) in cloacal swab specimens from an vaccinated chicken flock suspected with Newcastle Disease(ND) in continuous surveillance of long period of time. Heamagglutination inhibition(HI) titres were measured to determine the relationship between VNDV infectious rates and HI titres respresenting immunity of chickens at the same time. VNDV infection was still detectable in cloacal swab specimens from chickens 307 days postinfection. Furthermore, infection rate was gradully increasing with fall of HI levels. This result showed that VNDV could persist in flocks and transmit forever. However, flock may have a good egg production under certain infection rate by vaccination control. When infection rate increased to a certain degree, egg production fell and mortality rose. The result from study may play an important role in the control of ND in chicken flocks.