Histopathologic changes of spleen, trachea and mesenteric lymph nodes. (A) Red pulp of the spleen hemorrhage, hemosiderin macrophages increased significantly. (B) The control was normal. (C) Some mucosal epithelium of trachea swollen; neutrophil and plasma cells infiltrated in the lamina propria; lymphocytes proliferated; lymphocytic follicular increased. (D) The control was normal. (E) Macrophages and reticular cells proliferated and increased. (F) The control was normal.