SPONTANEOUS DIABETES-MELLITUS ASSOCIATED WITH PERSISTENT BOVINE VIRALDIARRHEA (BVD) VIRUS-INFECTION IN YOUNG CATTLE

Histologic and immunohistochemical studies were carried out on four yo ung cattle with diabetes mellitus associated with persistent bovine vi ral diarrhea (BVD) virus infection. Clinical findings included persist ent hyperglycemia, decreased glucose tolerance, glycosuria, polydipsia , and severe emaciation. Macroscopically, multiple erosions and ulcers in the mucosa of upper and lower alimentary tracts and swollen lymph nodes were commonly observed. Erosions and ulcers in the mucosa of ton gue, esophagus, and forestomach were represented histologically by nec rosis of squamous epithelium with neutrophilic infiltration. In the sm all and large intestines, villous atrophy and suppurative cryptitis we re often observed, along with diffuse infiltration of lymphocytes and macrophages and fibroplasia in the lamina propria. In the pancreas of all cattle, there was a reduction in the number of islet cells, and mo st of the residual islet cells had hydropic degeneration and a decreas ed number of secretory granules. Immunohistochemical examination confi rmed that these cells were severely degranulated beta-cells. In additi on, many islets containing necrotic islet cells were observed. These i slet cells had increased eosinophilia and shrinkage of cytoplasm, as w ell as pyknotic nuclei. Inflammation of the islets with mild infiltrat ion of lymphocytes was observed in all pancreatic lobes. In addition, bovine IgG-immunoreactive cells were identified immunohistochemically in the affected pancreatic islets. The BVD virus antigen was not ident ified in the cytoplasm of the islet cells by immunohistochemical study , although it was identified in the epithelial cells of the small inte stine. The histologic and immunohistochemical studies demonstrated tha t the pancreatic lesions in these animals were similar to those caused by acute insulin-dependent diabetes mellitus (IDDM) in human beings. These findings suggest that IDDM in Japanese Black cattle is an autoim mune disease induced through persistent infection by BVD virus.