Myxobolus arcticus and Parvicapsula minibicornis infections in sockeye salmon Oncorhynchus nerka following downstream migration in British Columbia

Mahony, Amelia; Johnson, Stewart C.; Neville, Chrys; Thiess, M. E.; Jones, Simon R. M.

doi:10.3354/dao03158

Cited by 5 publications

(4 citation statements)

References 47 publications

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“…Two of the most prevalent agents known to be transmitted in the freshwater environment, P. minibicornis and M. arcticus showed increasing prevalence upon entry to the marine environment, a result that was not expected but has recently been observed in juvenile Chinook salmon (Tucker et al, 2018). High estuarine abundance of the alternate host for P. minibicornis, Manayunkia speciosa , likely contributed to the sharp increase in the prevalence and load between Regions 1 (freshwater) and 2 (saltwater) (Kent, 2011; Mahony et al, 2017). In 2012 alone, both agents experienced a sharp rise in prevalence from Region 3 to 4.…”

Section: Discussionmentioning

confidence: 99%

Detection and Assessment of the Distribution of Infectious Agents in Juvenile Fraser River Sockeye Salmon, Canada, in 2012 and 2013

et al. 2018

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Infectious diseases may contribute to declines in Fraser River Sockeye salmon (Oncorhynchus nerka) stocks, but a clear knowledge gap exists around which infectious agents and diseases are important. This study was conducted to: (1) determine the presence and prevalence of 46 infectious agents in juvenile Fraser River Sockeye salmon, and (2) evaluate spatial patterns in prevalence and burden over initial seaward migration, contrasting patterns between 2 years of average and poor productivity. In total, 2,006 out-migrating Sockeye salmon were collected from four regions along their migration trajectory in British Columbia, in 2012 and 2013. High-throughput microfluidics quantitative PCR was employed for simultaneous quantitation of 46 different infectious agents. Twenty-six agents were detected at least once, including nine with prevalence >5%. Candidatus Brachiomonas cysticola, Myxobolus arcticus, and Pacific salmon parvovirus were the most prevalent agents. Infectious agent diversity and burden increased consistently upon smolts entry into the ocean, but they did not substantially change afterwards. Notably, both freshwater- and saltwater-transmitted agents were more prevalent in 2013 than in 2012, leading to an overall higher infection burden in the first two sampling regions. A reduction in the prevalence of two agents, erythrocytic necrosis virus and Paraneuclospora theridion, was observed between regions 2 and 3, which was speculated to be associated with mortality during the 1st month at sea. The most prevalent infectious agents were all naturally occurring. In a small number of samples (0.9%), seven agents were only detected around and after salmon farming regions, including four important pathogens: piscine orthoreovirus, Piscirickettsia salmonis, Tenacibaculum maritimum, and Moritella viscosa. As the first synoptic survey of infectious agents in juvenile Sockeye salmon in British Columbia, this study provides the necessary baseline for further research on the most prevalent infectious agents and their potential pathogenicity, which may adversely affect the productivity of valuable Sockeye salmon stocks. In addition, our findings are informative to the decision makers involved in conservation programs.

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Section: Discussionmentioning

confidence: 99%

Detection and Assessment of the Distribution of Infectious Agents in Juvenile Fraser River Sockeye Salmon, Canada, in 2012 and 2013

et al. 2018

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“…In Canada, M. viscosa ‐related disease is not common on salmon farms in BC. The disease has been reported only on the Atlantic coast and is usually referred to simply as “ulcer disease” rather than “winter ulcer disease,” because the onset of ulcer disease outbreaks in Atlantic salmon farms occurs between late summer and autumn when water temperatures exceed 10°C (MacKinnon et al, ). Ulcer disease mainly affects Atlantic salmon, and the disease has also been reported in other fish species, including Rainbow trout, sea water‐reared Brown trout, Atlantic cod ( Gadus morhua ) and European plaice ( Pleuronectes platessa L.).…”

Section: Synthesis Of Information About Infectious Agentsmentioning

confidence: 99%

Review of infectious agent occurrence in wild salmonids in British Columbia, Canada

Jia

Delphino

Awosile

et al. 2019

Journal of Fish Diseases

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Wild Pacific salmonids (WPS) are economically and culturally important to the Pacific North region. Most recently, some populations of WPS have been in decline. Of hypothesized factors contributing to the decline, infectious agents have been postulated to increase the risk of mortality in Pacific salmon. We present a literature review of both published journal and unpublished data to describe the distribution of infectious agents reported in wild Pacific salmonid populations in British Columbia (BC), Canada. We targeted 10 infectious agents, considered to potentially cause severe economic losses in Atlantic salmon or be of conservation concern for wild salmon in BC. The findings indicated a low frequency of infectious hematopoietic necrosis virus, piscine orthoreovirus, viral haemorrhagic septicaemia virus, Aeromonas salmonicida, Renibacterium salmoninarum, Piscirickettsia salmonis and other Rickettsia-like organisms, Yersinia ruckeri, Tenacibaculum maritimum and Moritella viscosa. No positive results were reported for infestations with Paramoeba perurans in peer-reviewed papers and the DFO Fish Pathology Program database. This review synthesizes existinginformation, as well as gaps therein, that can support the design and implementation of a long-term surveillance programme of infectious agents in wild salmonids in BC. K E Y W O R D SBritish Columbia, historical review, infectious agents, wild Pacific salmonids

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“…These patterns suggest a transmission scenario (TS-1) in which the actinospores occur in seawater adjacent to Vancouver Island with an abundance that varies seasonally and geographically. Alternatively, infections with P. minibicornis are acquired by juvenile and adult Pacific salmon and increase in prevalence and/or severity following salmon migration to the ocean or into the river to spawn [ 7 , 8 , 44 ]. These patterns are consistent with a transmission scenario (TS-2) in which actinospores are restricted to the estuary and/or lower reaches of some salmon natal rivers [ 13 ].…”

Section: Discussionmentioning

confidence: 99%

Parvicapsula pseudobranchicola in the northeast Pacific Ocean is rare in farmed Atlantic salmon Salmo salar despite widespread occurrence and pathology in wild Pacific salmon Oncorhynchus spp.

2023

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Background Infection with the myxozoan parasite Parvicapsula pseudobranchicola causes disease in wild and farmed salmonids in Norway. In the northeast Pacific Ocean, the parasite has been reported in Pacific salmon Oncorhynchus spp. without evidence of disease. The objectives of the present study were to confirm the identity of P. pseudobranchicola in the Pacific, document its host and geographic ranges, and describe associated pathological changes. Methods Ocean-entry year wild pink salmon Oncorhynchus gorbuscha, chum salmon O. keta, Chinook salmon O. tshawytscha, coho salmon O. kisutch and sockeye salmon O. nerka were collected in summer and autumn surveys near Vancouver Island (VI) and from a winter survey in the Gulf of Alaska. Samples were also obtained from farmed Atlantic salmon Salmo salar and Chinook salmon near VI. Samples were analysed by qPCR and histology using conventional staining or in situ hybridisation. Parasite sequence was obtained from small subunit ribosomal RNA gene (SSU rDNA). Results Identical 1525 base-pair SSU rDNA sequences from infected pink salmon, chum salmon and Chinook salmon shared 99.93% identity with a P. pseudobranchicola sequence from Norwegian Atlantic salmon. In autumn surveys, the prevalence was greatest in chum salmon (91.8%) and pink salmon (85.9%) and less so in Chinook salmon (68.8%) and sockeye salmon (8.3%). In farmed salmon, the prevalence was zero in Atlantic salmon (n = 967) and 41% in Chinook salmon (n = 118). Infections were preferentially sited in pseudobranch and visualised by in situ hybridisation. Heavy parasite burdens in all species of Pacific salmon were inconsistently associated with focal granulomatous pseudobranchitis. Conclusions In the northeast Pacific, widespread occurrence of P. pseudobranchicola in Pacific salmon together with its absence or sporadic occurrence in farmed Atlantic salmon differs from its epidemiology in Norway, despite similar pathological development in the pseudobranch. Consequences of the infections to the health of wild Pacific salmon, identity of the invertebrate host and the distribution and abundance of infective actinospores are unknown and remain high priorities for research. Graphical Abstract

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Myxobolus arcticus and Parvicapsula minibicornis infections in sockeye salmon Oncorhynchus nerka following downstream migration in British Columbia

Cited by 5 publications

References 47 publications

Detection and Assessment of the Distribution of Infectious Agents in Juvenile Fraser River Sockeye Salmon, Canada, in 2012 and 2013

Detection and Assessment of the Distribution of Infectious Agents in Juvenile Fraser River Sockeye Salmon, Canada, in 2012 and 2013

Review of infectious agent occurrence in wild salmonids in British Columbia, Canada

Parvicapsula pseudobranchicola in the northeast Pacific Ocean is rare in farmed Atlantic salmon Salmo salar despite widespread occurrence and pathology in wild Pacific salmon Oncorhynchus spp.

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