The lymphocytes of the medulla of bursa of Fabricius decreased in number 24 HPI,lymph node showed necrosis and reticulocytes proliferation in which we found acidophilic intranuclear inclusion bodies.

• 法氏囊24h髓质部淋巴细胞开始减少，85h淋巴滤泡开始坏死，网状内皮细胞增生，其内有嗜酸性核内包涵体，法氏囊病变逐渐加重。