Five types of lymphoid neoplasms in calves are described. Four cases with clinicopathologic features of the "calf form of lymphoma" were diagnosed as precursor B or T lymphoblastic leukemia. These neoplasms were positive for terminal deoxynucleotidyl transferase (TdT), a marker for immature lymphocytes. The fifth case (thymic B cell lymphoma) was also TdT positive, but was characterized by massive neoplastic involvement of the thymus. The sixth case involved bovine leukemia virus (BLV). As in the majority of previously reported BLV-associated cases, the neoplastic cells expressed CD5, and atypical giant cells were detected. Instead of enzootic bovine leukosis, in which at least two immunophenotypically distinct entities are included, a diagnosis of BLV-associated pleomorphic B-1 B cell lymphoma was made. The last case, involving an epitheliotropic γδ T cell lymphoma, was characterized by epitheliotropism in the gastrointestinal tract and WC1 expression. Since several histologic types of lymphoid neoplasm occur in calves, the term "calf form of lymphoma" should be abandoned for accurate diagnosis.
Epidemiology, pathology, and immunohistochemistry were investigated in layer hens affected with H5N1 highly pathogenic avian influenza, which occurred for the first time in 79 years in Japan. The farm, which had a total of 34,640 chickens, experienced up to 43.3% mortality before the chickens were depopulated. Clinically, the affected chickens exhibited mortality without apparent clinical signs. Histologically, hepatocytic necrosis; necrosis of ellipsoids and follicles with fibrin in the spleen; necrosis with glial nodules in the brain stem, cerebrum, and cerebellum; necrosis of acinar cells in the pancreas; and necrosis of lymphoid tissues in intestinal lamina propria were seen. Occasionally, mild bronchiolitis, degeneration of smooth muscle fibers in the cecum, and mild tubulonephrosis were noted. Immunohistochemically, influenza virus antigens were detected often in the liver and spleen, heart, intestine, gizzard, proventriculus, and oviduct. In addition, antigens were seen also in the brain, kidney, pancreas, and ovary, but seldom in the lung and trachea. Virus antigen was mainly detected in the capillary endothelium and parenchymal cells. This suggests that virus excretion from the respiratory tract was not as prevalent as that from the digestive tract in the present cases.
There was a high incidence of sudden death due to haemonchosis in a sheep herd, where a regular anthelmictic program using diethylcarbamazine had been conducted. When a new anthelmintic program using ivermectin (IVM) or levamisole (LEV) was conducted over three years, the mortality apparently decreased from approximately 20% to 2.8% in the third year. The anthelmintic effects were poor with minimal reduction in egg per gram (EPG) in the pour-on route of IVM, but were significantly higher with a major reduction in the average EPG from 5418.5 to 3.2 in the subcutaneous route of IVM and from 98.2 to 1.9 in the oral route of LEV after administration for one month. However, the anthelmintic effects after two months of administration in the subcutaneous route of IVM were lower than those of the one-month interval, in which the reduction of EPG was from 120.5 to 41.1, indicating no significance.Moreover, despite the significantly higher anthelmintic effects at first administration of both IVM and LEV for each year, the EPGs were gradually decreased after the second administration.This may indicate the occurrence of drug-resistant worms.
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