1985/86年に発生した水無脳症-小脳形成不全症候群を伴う先天性異常子牛発生の疫学調査と本病の原因ウイルスと考えられるChuzanウイルスの血清疫学的調査

An epidcmic of congenital abnormalities of calves characterized by the hydranencephaly-cerebellar hypoplasia (HCH) syndrome occurred in the Kyushu district of Japan from November 1985to April 1986. The numbcr of animals suffering from the disease was 2, 463. The disease occurred mair1ly in bcef cows and was rarely seen in milk cattle. SeroepidemioIogical survey revealcd that antibody to Chuzan virus, a new orbivirus, was present at a high rate iri the Kyushu district (southwestern part of Japan), and at a low rate in the Chugoku and Shikoku district (western part of Japan). The distribution of the antibody-positive reactors coincided with the area of occurrence of the disease. Also the time of prevalence of Chuzan virus agreed with the time of occurrence of the congenital abnormalities. Thesc findings supported the previous conclusion that Chuzan virus may havc a very closc rcIationship with the occurrence of the congenital abnormalities of calves. Seroepidemio1o-gical investigations revealed that Chuzan virus was never prevalcnt in Kyushu beforc thc epidemic of HCH syndrome and that it first appeared in the southernmost island of Japan and then wcnt north to the main islands of Japan.