As a part of gastrointestinal tract , the stomach works like a mixer , churning and mashing the food into a sloppy soup while the small intestine has tiny projections ( villi ) which increase its surface area by a factor of 600 消化道的胃部就像个搅拌器，将食物捣成稀糊。小肠内也密布细小的绒毛，使小肠的表面积增加达600倍。
Developed folds , villi and microvilli on the surface of the epithelium increase surface of absorptive largely . therefore , efficiency of digestion , absorption , endocrine secretion and mucous immunology was raised 鳖消化道腔面具有发达的皱襞、绒毛和微绒毛，大大增加了粘膜表面积，从而提高了其消化吸收、内分泌和粘膜免疫机能的效率。
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 动物回归试验中接种两周龄spf鸡， 24h后陆续发病，表现为持续性水样腹泻；剖检可见病鸡脱水、小肠内有大量的液体和气泡、肠粘膜变薄；组织学变化为肠绒毛上皮坏死、脱落，绒毛平均长度减少而隐窝深度增加，固有层中淋巴细胞浸润。其临床症状及病理组织学变化与自然发病相同。
