Parvicapsula pseudobranchicola in salmonids in British Columbia
Parvicapsula pseudobranchicola is a parasitic myxospore that causes the disease parvicapsulosis in farmed Atlantic salmon (Salmo salar) in Norway (Karlsbakk et al., 2002; Sterud et al., 2003). The disease is associated with mortality ranging from 2% to 40% and the affected fish are lethargic, often swimming near the surface with uncoordinated movements. Two species of Parvicapsula have been described from salmonids in British Columbia (B.C.). The first, Parvicapsula minibicornis occurs in kidney of Sockeye salmon (Oncorhynchus nerka) and several other salmon species (Oncorhynchus spp.) that spawn in the Fraser River drainage basin (Kent et al., 1997; Jones et al., 2003). The second, Parvicapsula kabatai occurs in kidney of Pink salmon (O. gorbuscha) from northern Vancouver Island (Jones et al., 2007). An unidentified Parvicapsula sp. was reported from kidney of cage-reared Coho salmon (O. kisutch) in British Columbia (Kent, 1998) and from pen-reared Coho, Chinook (O. tshawytscha), Masu (O. masou), and Atlantic salmon, and in Cutthroat trout (Oncorhynchus clarkii) from Puget Sound, Washington (Hoffman, 1984; Johnstone, 1984). In BC, molecular evidence of P. pseudobranchicola was reported from 13 of the 79 juvenile sockeye salmon that had been predated by rhinoceros auklets (Miller et al., 2014) and in 12 of the 47 Chinook salmon (Bass et al., 2017). Kidney from 165 Pink salmon had molecular evidence of P. kabatai (15%) or P. pseudobranchicola (38%) and both parasites were found together in approximately 10% of the fish (Jones et al. unpublished data). Despite the molecular findings, there are no reports of P. pseudobranchicola or of parvicapsulosis in farmed Atlantic salmon in B.C. The purposes of FHTT-2019-P-03 are to ascertain the utility of the published P. pseudobranchicola quantitative PCR assay (Jørgensen et al., 2011); to detect the parasite in B.C. salmon; and to determine its prevalence, distribution and impact in B.C. farmed Atlantic salmon and wild Pacific salmon.
Program for Aquaculture Regulatory Research (PARR)
Research scientist, Pacific Biological Station, Nanaimo, B.C.
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