Pathogenicity and tumorigenicity of Oncorhynchus masou virus (OMV) isolated from cultured coho salmon Oncorhynchus kisutch in Hokkaido, Japan

• Published in: Suisan Zoshoku Vol. 71; no. 4
• Main Authors: Katsumata, Yoshitomo, Mizuno, Shinya, Nagata, Jun, Kasai, Hisae, 義友, 勝又, 伸也, 水野, 永田 淳, 久会, 笠井
• Format: Journal Article
• Language: English; Japanese
• Published: Tsu Japan Science and Technology Agency 01.01.2023
• Subjects: Aquaculture; Carnivorous animals; Experimental infection; Fingerlings; Freshwater fishes; Fry; Infections; Mass mortality; Mortality; Neoplasms; Oncorhynchus keta; Oncorhynchus kisutch; Oncorhynchus masou; Pathogenicity; Pathogens; Salmon; Strains (organisms); Tumorigenicity; Viral infections; Viruses; Japan
• ISSN: 0371-4217; 2185-0194
• DOI: 10.11233/aquaculturesci.71.153

In 2017, an outbreak of Oncorhynchus masou virus disease (OMVD) caused mass mortality of adult coho salmon Oncorhynchus kisutch at an aquaculture farm in Hokkaido, Japan. Our aim was to reveal the pathogenicity and tumorigenicity of OMV strain CSHK-002 isolated from coho salmon reared on the farm. Experimental infection revealed that CSHK-002 caused higher cumulative mortality in coho salmon (66% in fry and 24% in fingerling) than in masu salmon O. masou (10% in fry). Meanwhile, infection with OMV OO-7812, an oncogenic strain previously isolated from masu salmon, exhibited contrary results: the viral infection did not affect viability in coho salmon but caused a cumulative mortality of 46% in masu salmon. Similar to OMV OO-7812 (78% cumulative mortality), CSHK-002 caused high cumulative mortalities (50%) in chum salmon O. keta fry, indicating that CSHK-002 poses a high risk to the chum salmon industry. Experimental infection of coho salmon with CSHK-002 did not induce formation of tumors. Furthermore, tumor formation was not observed in the aquaculture farm between 2017 and 2022. Therefore, unlike OMV strains previously isolated from coho salmon, CSHK-002 is unlikely to be tumorigenic. These findings suggest that CSHK-002 exhibits characteristics that are distinct from those of previous OMV strains.