北日本におけるサケ科魚類採卵親魚の魚類ウィルス保有状況について ― 昭和51年～昭和61年 ―

北海道さけ・ますふ化場研究報告

From September 1976 to November 1986, we collected 5,068 ovarian fluid specimens from 5 species of 10,028 females and 21 seminal specimens from 2 species of 155 males of mature salmonid fish, including to masu (Oncorhynchus masu), chum (O. keta), pink (O. gorbuscha), kokanee salmon (O. nerka) and rainbow trout (Salmo gairdneri) from 26 catching stations located in Hokkaido and 5 places in Honshu (the main island of Japan), 6 hatcheries in Hokkaido and 7 in Honshu and 10 fish farms and 1 lake in Hokkaido. Also, 161 mixed kidney and spleen specimens were taken from 805 of these fish. Furthermore, 139 tumor tissues observed among 4,288 fish were employed for virus inspection. Blood smears prepared from 660 fish were employed in microscopical examination for evidence of VEN, and thin sections of blood of these were observed by electron microscopy. Four viruses have been isolated during the course of this investigation. IHNV was found in ovarian fluid of chum salmon from Abashiri River in 1976. During the period from 1976 through 1986, IHNV has been recovered 9 times from fish at 7 collection sites. OMV was first discovered in 1978 from masu salmon at Otobe Salmon Hatchery. At all sites permitting collection of 60 specimens with the exception of 3 hatchery, OMV has subsequently been isolated from ovary fluid or from epithelial tumor tissue around the mouth of mature masu salmon. It has not been found in the other species of fish. Incidence of OMV has decreased since we suggested iodophore treatment at the eyed egg stage. CSV was isolated from the kidney of healthy chum salmon at Tokushibetsu Hatchery in 1978 but during the period from 1979 through 1986, CSV has not been found from mature fish. IPNV was isolated from tumor tissue of masu salmon at Aomori Prefectural Fisheries Experimental Station in 1981, at this time IHNV and OMV were isolated from the same tumor tissue.