The histologic lesions were characterized by the remarkable atrophy of intestinal villi , basal vacuolation of enterocytes , increment of the crypt and the villus - to - crypt ratio had significantly decrease . compared with that of noninoculated control chicks . besides . intestinal villi become thin and flat . or cubic , also accompanied with necrosis . many villous enterocytes were detached from the lamina propria and the lamina propria contained a diffuse infiltrate of lymphocytes , plasma cells , macrophages . the characteristic ultrastructural changes observed by electronmicroscope were swelled mitochondria and dilated endo - plasticreticulum . ribosome on the surface of endo - plasticreticulum fall off and the number of ribosome within the cell decrease 動物回歸試驗中接種兩周齡spf雞, 24h后陸續發病,表現為持續性水樣腹瀉;剖檢可見病雞脫水、小腸內有大量的液體和氣泡、腸粘膜變薄;組織學變化為腸絨毛上皮壞死、脫落,絨毛平均長度減少而隱窩深度增加,固有層中淋巴細胞浸潤。其臨床癥狀及病理組織學變化與自然發病相同。