All the 170 14-day-old chickens were divided into 10 groups,the seven experiment groups were infected with 7 strains(M41,Aust-T,H120,H52,Sh1,Sh2,Sh3),while the other three control groups were infected with AIV,NDV and IBDV,respectively.

• 分别用IBV T株、M41、H52、H120、上海野毒(Sh1、Sh2、Sh3)对7个试验组的鸡攻毒,分别用AIV、NDV以及IBDV对3个对照组鸡攻毒,然后定期剖杀采样,并用套式RT-PCR方法进行检测。