Ibaraki virus, an agent of epizootic disease of cattle resembling bluetongue. I. Epidemiologic, clinical and pathologic observations and experimental transmission to calves.

Abstract

Outbreaks of an acute febrile disease of cattle occurred in Japan in 1959 and 1960. Its occurrence was limited in late summer and autumn, and in Kyushu, Shikoku and Honshu roughly south of 37 degrees north latitude, suggesting a close correlation ofthe incidence with the climatic onditions, hence a possibility ofthe presence of arthropod vector. The disease was characterized byfever and lesions affecting the mucous membrane and skin, musculature and vascular system. Degeneration f striated muscles was observed in the esophagus, larynx, pharynx, tongue and skeletal muscular system. Edema and hemorrhage were marked in the mouth, lips, abomasum, coronets etc., occasionally followed by degeneration fthe epithelium leaving erosions or ulcerations. Severe lesions affecting the esophageal nd laryngopharyngeal musculature caused deglutitive difficulty which in turn resulted in dehydration and emaciation, and occasionally in aspiration pneumonia, constituting the major causes of death of the affected animals. These findings indicate that the disease resembles bluetongue in sheep and cattle. The clinical materials obtained from natural cases induced a clinical i lness when inoculated into calves, and the disease was transmitted serially in calves by intravenous inoculation ofthe blood obtained at the height of febrile reaction. The experimentally produced isease was clinically and pathologically indistinguishable from the natural disease. An outbreak of an acute febrile disease of cattle swept over the central and western parts of Japan during the months from August through December in 1959. A more limited outbreak of the disease occurred in the central Japan from September to December in 1960. The disease was characterized by fever, stomatitis and deglutitive difficulty. The clinical, and pathologic picture was very reminiscent of bluetongue in sheep and cattle. The disease was readily transmitted to calves by inoculation with the blood or tissues from naturally affected cattle. A cytopathogenic virus was recovered in bovine cell cultures from naturally and experimentally infected cattle. The isolated virus, designated as •gIbaraki virus•h, was found to resemble bluetongue