Bovine epizootic fever. I. Propagation of the virus in the suckling hamster, mouse and rat, and hamster kidney BHK21-WI2 cell.

A virus, the Yamaguchi strain, was serially propagated in suckling hamsters, mice and rats, and hamster kidney BHK21-WI2 cells from a natural case in the 1966 outbreak of bovine epizootic fever, an acute febrile disease of cattle, resembling ephemeral fever, known in Japan since 1949. An acute phase blood from the natural case was first passaged in calves by intravenous inoculation, and a blood specimen at the second passage was used to initiate serial hamster passage. Infected hamsters died with nervous symptoms, and serial passage was readily accomplished by intracerebral inoculation with brain emulsions. The hamster passage line of virus was serially passaged by intracerebral inoculation in 1-or 2-day-old mice, and then in rats 1 or 2 days after birth, which developed fatal encephalitis. The hamster passage virus was also serially propagated with cytopathic effect in cultures of BHK21-W12 cell cultures. These viral lines were shown to be neutralized by, and to produce specific complement-fixing antigen reactive with, convalescent sera of calves infected with the original Yamaguchi strain, confirming the identity of these lines as the Yamaguchi strain. The hamster passage line, when inoculated intravenously in calves, induced an acute febrile illness which was similar to bovine epizootic fever; all the inoculated calves had viremia and developed neutralizing and complement-fixing antibodies against the virus. Serological evidence for infection with this virus was obtained in natural cases in the 1966 outbreak. These findings seem to justify this virus to be the causative agent of bovine epizootic fever. Bovine epizootic fever is an acute febrile disease of cattle known in Japan since 1949. The disease has a sudden onset with fever, and the recovery occurs usually in 2 or 3 days. The disease is characterized essentially by respiratory symptoms with increased respiration and a temporary dyspnea, nasooro-pharyngeal secretions and lacrimation. Anorexia, decreased lactation, joint pain and muscle tremor are common. The case fatality is low, less than one percent. The disease has a seasonal incidence; outbreaks begin late in summer and terminate late in autumn or early in winter. The occurrence of the disease is limited in the central and western parts of Japan, and the disease has never been reported in the northern parts, Tohoku and Hokkaido. It should be noted