The virulence of four IBDV is different,isolates H 3,H 4 are more virulent than H 1,H 2 and they have the properties of making the Bursa of Faricius atrophy rapidly.

• 结果表明，各毒株毒力有一定差异，其中H3、H4株毒力高于H1、H2株，且有迅速致法氏囊萎缩的特性；