Viral Diseases of Cultured Fishes in Japan

要旨

Three proved and two suspected viral diseases of cultured fishes in Japan were introduced in this paper. They are of salmonids and eel. As for IPN and IHN, research works were reviewed.From an epizootic of European and Japanese eel producing severe mortality, a virus was isolated in RTG-2 cells, being the closest to Fr 21 among five serotypes of IPN virus. Virus particles were found in cytoplasm of the kidney cells of eel of natural epizootic and in RTG-2 cells infected with the isolant. They are pentagonal or hexagonal having a diameter 68 to 77 mμ. This virus fulfilled the River's postulates.On an epizootic of landlocked nerka fry, virological diagnosis was tried using RTG-2 cells and proved a syncytium-forming agent. Viral particles, being similar shape to Herpesvirus were found in the process of budding on the surface of RTG-2 cell having a diameter 220 to 250 mμ. From an epizootic of American eel, a virus was isolated in RTG-2 cells, not being neutralized with either rabbit antisera of IHN and VHS. This virus particles are bullet shape having 140 to 150mμlong.Histopathological findings on these natural epizootic indicate generally regressive pathological change. Severely affected eels EVE show nephrosis, glomerulonephritis and splenic change. With NeVTA disease, affected nerka fry show granular degeneration in skeletal musculature, syncytium-formation and cytoplasmic inclusion in interstitial cells on the kidney. In EVA-affected American eel, hemorrhage and degeneration in skeletal musculature, hyperemia in branchial vessels as well as hemorrhage into Bowman's space are found as principal change.

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