<i>Flavobacterium psychrophilum</i> Infections in Salmonid Broodstock and Hatchery‐Propagated Stocks of the Great Lakes Basin

Vliet, Danielle Van; Loch, Thomas P.; Faisal, Mohamed

doi:10.1080/08997659.2015.1088488

Cited by 19 publications

(15 citation statements)

References 38 publications

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“…It is also interesting that for the feral fish in the GLB and in particular for Chinook salmon (which harbor the highest F. psychrophilum infection prevalence among the 3 Oncorhynchus spp. that were recently examined) (36), data from this study do not seem to indicate an epidemic population structure, as demonstrated by the lack of dominant STs or CCs. It is also only among these fish that we observed infections by the same ST (e.g., ST256) or CC (e.g., CC-ST256) in different fish host species.…”

Section: Discussioncontrasting

confidence: 65%

“…DNA was extracted from each suspected F. psychrophilum isolate using the DNeasy blood and tissue kit (Qiagen), according to the manufacturer's protocol for Gram-negative bacteria. For a portion of the isolates, the F. psychrophilum-specific primers of Toyama et al (39) were used to PCR amplify a partial stretch of the 16S rRNA gene as previously described (36). The remaining isolates were confirmed to be F. psychrophilum using PCR amplification with degenerate universal primers (40) and Sanger sequencing as previously reported (41).…”

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confidence: 99%

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Genetic Diversity of Flavobacterium psychrophilum Isolates from Three Oncorhynchus spp. in the United States, as Revealed by Multilocus Sequence Typing

Vliet

Wiens

Loch

et al. 2016

Appl Environ Microbiol

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The use of a multilocus sequence typing (MLST) technique has identified the intraspecific genetic diversity of U.S. Flavobacterium psychrophilum, an important pathogen of salmonids worldwide. Prior to this analysis, little U.S. F. psychrophilum genetic information was known; this is of importance when considering targeted control strategies, including vaccine development. Herein, MLST was used to investigate the genetic diversity of 96 F. psychrophilum isolates recovered from rainbow trout (Oncorhynchus mykiss), coho salmon (Oncorhynchus kisutch), and Chinook salmon (Oncorhynchus tshawytscha) that originated from nine U.S. states. The isolates fell into 34 distinct sequence types (STs) that clustered in 5 clonal complexes (CCs) (n ‫؍‬ 63) or were singletons (n ‫؍‬ 33). The distribution of STs varied spatially, by host species, and in association with mortality events. Several STs (i.e., ST9, ST10, ST30, and ST78) were found in multiple states, whereas the remaining STs were localized to single states. With the exception of ST256, which was recovered from rainbow trout and Chinook salmon, all STs were found to infect a single host species. Isolates that were collected during bacterial cold water disease outbreaks most frequently belonged to CC-ST10 (e.g., ST10 and ST78). Collectively, the results of this study clearly demonstrate the genetic diversity of F. psychrophilum within the United States and identify STs of clinical significance. Although the majority of STs described herein were novel, some (e.g., ST9, ST10, ST13, ST30, and ST31) were previously recovered on other continents, which demonstrates the transcontinental distribution of F. psychrophilum genotypes. IMPORTANCEFlavobacterium psychrophilum is the causative agent of bacterial cold water disease (BCWD) and rainbow trout fry syndrome (RTFS) and is an important bacterial pathogen of wild and farmed salmonids worldwide. These infections are responsible for large economic losses globally, yet the genetic diversity of this pathogen remains to be fully investigated. Previous studies have identified the genetic diversity of this pathogen in other main aquaculture regions; however, little effort has been focused on the United States. In this context, this study aims to examine the genetic diversity of F. psychrophilum from the United States, as this region remains important in salmonid aquaculture.T he causative agent of bacterial cold water disease (BCWD) and rainbow trout fry syndrome (RTFS), Flavobacterium psychrophilum, is an important bacterial pathogen of wild and farmed salmonids worldwide (1). In addition to horizontal transmission, F. psychrophilum is suspected of being vertically transmitted (2-5) and appears to resist standard povidone-iodine treatment during egg disinfection (4, 6, 7), which make efforts to control this bacterium particularly problematic. Since the initial isolation of F. psychrophilum in North America (8), F. psychrophilum infections have been reported in Europe, South America, Asia, and Australia (9-11) and from all of...

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Section: Discussioncontrasting

confidence: 65%

mentioning

confidence: 99%

Genetic Diversity of Flavobacterium psychrophilum Isolates from Three Oncorhynchus spp. in the United States, as Revealed by Multilocus Sequence Typing

Vliet

Wiens

Loch

et al. 2016

Appl Environ Microbiol

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“…Bacterial genomic DNA was extracted using the DNeasy Blood and Tissue kit (Qiagen, Inc., Valencia, CA) according to the manufacure's protocol for Gram-negative bacteria, quantified using a Qubit fluorometer (Life Technologies, Grand Island, NY), and then diluted to 20 ng/l. Prior to MLST analyses, the identity of all isolates was confirmed as F. psychrophilum using the conventional PCR assay of Toyama et al (35) as detailed previously (36).…”

Section: Methodsmentioning

confidence: 99%

Large-Scale Analysis of Flavobacterium psychrophilum Multilocus Sequence Typing Genotypes Recovered from North American Salmonids Indicates that both Newly Identified and Recurrent Clonal Complexes Are Associated with Disease

Knupp

Wiens

Faisal

et al. 2019

Appl Environ Microbiol

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Flavobacterium psychrophilum, the etiological agent of bacterial coldwater disease (BCWD) and rainbow trout fry syndrome (RTFS), causes significant economic losses in salmonid aquaculture, particularly in rainbow trout (Oncorhynchus mykiss). Prior studies have used multilocus sequence typing (MLST) to examine genetic heterogeneity withinF. psychrophilum. At present, however, its population structure in North America is incompletely understood, as only 107 isolates have been genotyped. Herein, MLST was used to investigate the genetic diversity of an additional 314 North AmericanF. psychrophilumisolates that were recovered from ten fish host species from 20 U.S. states and 1 Canadian province over nearly four decades. These isolates were placed into 66 sequence types (STs), 47 of which were novel, increasing the number of clonal complexes (CCs) in North America from 7 to 12. Newly identified CCs were diverse in terms of host association, distribution, and association with disease. The largestF. psychrophilumCC identified was CC-ST10, within which 10 novel genotypes were discovered, most of which came fromO. mykissexperiencing BCWD. This discovery, among others, provides evidence for the hypothesis that ST10 (i.e., the founding ST of CC-ST10) originated in North America. Furthermore, ST275 (in CC-ST10) was recovered from wild/feral adult steelhead and marks the first recovery of CC-ST10 from wild/feral fish in North America. Analyses also revealed that at the allele level, the diversification ofF. psychrophilumin North America is driven three times more frequently by recombination than random nucleic acid mutation, possibly indicating how new phenotypes emerge within this species.IMPORTANCEFlavobacterium psychrophilumis the causative agent of bacterial coldwater disease (BCWD) and rainbow trout fry syndrome (RTFS), both of which cause substantial losses in farmed fish populations worldwide. To better prevent and control BCWD and RTFS outbreaks, we sought to characterize the genetic diversity of several hundredF. psychrophilumisolates that were recovered from diseased fish across North America. Results highlighted multipleF. psychrophilumgenetic strains that appear to play an important role in disease events in North American aquaculture facilities and suggest that the practice of trading fish eggs has led to the continental and transcontinental spread of this bacterium. The knowledge generated herein will be invaluable toward guiding the development of future disease prevention techniques.

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“…Specifically for Flavobacterium psychrophilum, molecular confirmation was performed as previously described (Van Vliet et al. ).…”

Section: Methodsmentioning

confidence: 99%

Resurgence of Salmonid Herpesvirus‐3 Infection (Epizootic Epitheliotropic Disease) in Hatchery‐Propagated Lake Trout in Michigan

et al. 2019

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Over the past century, populations of Lake Trout Salvelinus namaycush have declined throughout the Great Lakes basin due to overfishing, habitat destruction, introduction of invasive species, and associated recruitment issues from high thiaminase, as well as emerging infectious diseases. To combat these declines, state and federal fishery management agencies undertook substantial stock enhancement efforts, including more stringent regulation of sport and commercial catch limits and increasing hatchery propagation of Lake Trout stocked into Great Lakes basin waterways. One state fish hatchery involved in these rehabilitation efforts experienced mass mortality events in 2012 and 2017. In 2012, following a period of abnormally heavy rain, hatchery staff observed abnormal behavior followed by increased mortalities in two strains of Lake Trout fingerlings, reaching upwards of 20% mortality and totaling a loss of approximately 100,000 fish. In 2017, following another heavy-rain season, 6-8% of 2-year-old Lake Trout experienced morbidity and mortality similar to that observed in 2012. During the 2012 event, Brook Trout Salvelinus fontinalis and splake (Lake Trout × Brook Trout hybrid) reared in flow-through systems receiving water from diseased Lake Trout remained clinically unaffected. Molecular analyses revealed all lots of affected Lake Trout were infected with the salmonid herpesvirus-3 (epizootic epitheliotropic disease virus [EEDV]), a disease that caused complete depopulation of this hatchery in the late 1980s and until 2012 was never again detected in this hatchery or in Michigan. Further sampling detected EEDV in apparently healthy 5-year-old Lake Trout and in wild Mottled Sculpin Cottus bairdii collected in the hatchery source water. The ability of the virus to replicate in tissues of infected fish was verified by exposing naïve Lake Trout to the filtered tissue homogenates of infected fish resulting in similar disease signs. Despite the virus going undetected for many years, these two EEDV episodes clearly demonstrate the continued presence of this deadly herpesvirus in the Great Lakes basin. METHODSLake Trout mortality events.-In September of 2012, Michigan's Upper Peninsula experienced several days of heavy, warm rain, resulting in the flooding of many 32 FAISAL ET AL.

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Flavobacterium psychrophilum Infections in Salmonid Broodstock and Hatchery‐Propagated Stocks of the Great Lakes Basin

Cited by 19 publications

References 38 publications

Genetic Diversity of Flavobacterium psychrophilum Isolates from Three Oncorhynchus spp. in the United States, as Revealed by Multilocus Sequence Typing

Genetic Diversity of Flavobacterium psychrophilum Isolates from Three Oncorhynchus spp. in the United States, as Revealed by Multilocus Sequence Typing

Large-Scale Analysis of Flavobacterium psychrophilum Multilocus Sequence Typing Genotypes Recovered from North American Salmonids Indicates that both Newly Identified and Recurrent Clonal Complexes Are Associated with Disease

Resurgence of Salmonid Herpesvirus‐3 Infection (Epizootic Epitheliotropic Disease) in Hatchery‐Propagated Lake Trout in Michigan

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