牛の “ハイエナ病” の発生例

Abstract

An outbreak of “hyena disease” in cattle was recognized on a farm that had bredabout one thousand Holstein cattle, in Iwate Prefecture over a period from June through August, 1984. Of 82 calves of almost the same age, 40 were affected. They exhibited a low growth rate marked in the hindquarters and defective locomotion which became apparent at about six months of age. Pathological and serological examination were carried out in fourteen cases. Autopsy revealed shortening of the femur and tibia. The shortened femur was mostly accompanied with flattening of the head, as well as twisting of the head and neck. Shortening of the humerus and flattening of its head were also recognized in all the four cases examined. The epiphyseal cartilaginous plates of the femur, tibia and humerus partially disappeared or deformed. Similar lesions were seen also in the vertebra, although only two cases were examined. Low growth of skeletal muscle was noted in the hind legs.Histologically, the resting zone of cartilage of the epiphyseal cartilaginous plate was thickened. Cartilaginous cells decreased in number and disappeared in the proliferative zone. Excessive infiltration of osteoblasts and osteoclasts was seen. Perivascular cuffing of small round cells in the central nervous system was found in 7 cases. Infiltration of small round cells was noticed in the neurohypophysis of 2 cases and in the heart of 6 cases. Neutralizing antibodies against bovine viral diarrheamucosal disease virus were demonstrated in the serum of 5 cases.