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K L Hammell - One of the best experts on this subject based on the ideXlab platform.
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Risk factors associated with time to first clinical case of Bacterial Kidney Disease (BKD) in farmed Atlantic Salmon (Salmo salar L.) in New Brunswick, Canada
Preventive veterinary medicine, 2017Co-Authors: A.s. Boerlage, Henrik Stryhn, J Sanchez, Adel Elghafghuf, K L HammellAbstract:Infection with Renibacterium salmoninarum, the cause of Bacterial Kidney Disease (BKD) occurs in salmon populations in many locations, including the east coast of Canada. However, information about risk factors for BKD and their effects in the saltwater phase of the salmon aquaculture industry in the region is inadequate. We conducted a retrospective observational cohort study using industry health records in which BKD was recorded in New Brunswick, Canada, between 2006 and 2012. Several risk factors for BKD, such as stocking season, mortality percentage in the first four weeks, food conversion ratio (FCR), lice treatment, Bay Management Area (BMA), and production year were analyzed in a survival analysis using Cox proportional hazards models with cross-classified random effects to account for the structure of the data. The models incorporated effects on two different time scales, time since stocking and calendar time. The risk period was from stocking in salt water to first occurrence of clinical BKD in a pen. Results were time varying. Stocking season had a pronounced effect on time to clinical BKD after middle October of the first year after stocking, with clinical cases occurring less frequently in fall/winter-stocked fish compared to summer and spring-stocked fish; for example, in middle October, the Hazard Ratio of spring- compared to fall/winter-stocked fish was 15.8 (95% CI; 1.05, 354). Differences lasted until June and July of the second year after stocking. Effects of final hatchery before transfer to seawater, and egg source were not detected, but a limitation of this study was that this information was not available for 44.3% of the fish groups in our dataset. BKD status of a site/pen before fallow period and distance to nearest site with BKD were also not detected. Feed conversion ratio and mortality during the first four weeks affected BKD, indicating that better performing fish have a reduced hazard for BKD or vice versa, and implying that good general husbandry practices and BKD are correlated.
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Bayesian latent class analysis of diagnostic sensitivity and specificity of tests for surveillance for Bacterial Kidney Disease in Atlantic salmon Salmo salar
Aquaculture, 2017Co-Authors: Diana Jaramillo, Henrik Stryhn, Holly Burnley, Ian A. Gardner, K L HammellAbstract:Abstract Bacterial Kidney Disease (BKD) diagnosis is often carried out by IFAT, ELISA, and PCR because these tests yield rapid results compared with Bacterial culture for the causative agent, Renibacterium salmoninarum. However, the diagnostic sensitivity (DSe) and specificity (DSp) of these tests is generally unknown, particularly in subclinically infected Atlantic salmon. Bayesian models were used to analyse test results from 454 field samples sourced from salmon populations with different infection status and submitted to independent laboratories. Results showed that DSe was highly dependent on the presentation of infection. When applied to fish with BKD-associated gross lesions, the highest to lowest posterior medians for DSe were: PCR2 (0.98), PCR1 (0.97), Bacterial culture (0.86), ELISA (0.82) and IFAT (0.75). When applied to fish without lesions, the posterior medians for DSe were: PCR1 (0.82), PCR2 (0.82), Bacterial culture (0.29), IFAT (0.29) and ELISA (0.21). The posterior medians for DSp were similar in populations with and without lesions. ELISA had the highest DSp (0.99), followed by culture (0.98–0.99), IFAT (0.96), PCR1 (0.94–0.96) and PCR2 (0.83–0.84), where different numbers reflect the estimates for populations with or without lesions respectively. Among tests that were evaluated for intra-laboratory repeatability (ELISA, PCR1 and IFAT), ELISA had the highest repeatability (kappa = 0.82). We concluded that PCR tests were the fittest of the evaluated tests for the purpose of screening subclinically-infected adult Atlantic salmon.
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Case definition for clinical and subclinical Bacterial Kidney Disease (BKD) in Atlantic Salmon (Salmo salar L.) in New Brunswick, Canada
Journal of fish diseases, 2016Co-Authors: A.s. Boerlage, Henrik Stryhn, J Sanchez, K L HammellAbstract:Bacterial Kidney Disease (BKD) is considered an important cause of loss in salmon aquaculture in Atlantic Canada. Causative agent of BKD is the Gram-positive bacteria Renibacterium salmoninarum. Infected salmon are often asymptomatic (subclinical infection), and the Disease is considered chronic. One of the challenges in quantifying information from farm production and health records is the application of a standardized case definition. Case definitions for farm-level and cage-level clinical and subclinical BKD were developed using retrospective longitudinal data from aquaculture practices in New Brunswick, Canada, combining (i) industry records of weekly production data including mortalities, (ii) field observations for BKD using reports of veterinarians and/or fish health technicians, (iii) diagnostic submissions and test results and (iv) treatments used to control BKD. Case definitions were evaluated using veterinarians' expert judgements as reference standard. Eighty-nine and 66% of sites and fish groups, respectively, were associated with BKD at least once. For BKD present (subclinical or clinical), sensitivity and specificity of the case definition were 75-100% varying between event, fish group, site cycle and level (site pen). For clinical BKD, sensitivities were 29-64% and specificities 91-100%. Industry data can be used to develop sensitive case definitions.
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randomized clinical field trial of a Bacterial Kidney Disease vaccine in atlantic salmon salmo salar l
Journal of Fish Diseases, 2010Co-Authors: T A Burnley, Henrik Stryhn, Holly Burnley, K L HammellAbstract:A randomized, blinded clinical trial was performed to assess the relative effectiveness of five commercial and one experimental vaccine in a population of farmed fish experiencing a Bacterial Kidney Disease (BKD) outbreak that occurred in one study cage that was part of a larger clinical field trial. A total of 6000 uniquely identified Atlantic salmon S1 presmolts were randomly assigned to vaccine groups in the hatchery and transferred to a commercial marine aquaculture site. Repeated sampling events to evaluate growth, inherent physical conditions and health status were carried out over the entire production cycle. During the second summer at sea, the study cage developed an outbreak of BKD that lasted approximately 240 days. The effectiveness of the selected vaccines was evaluated using survival analysis methods. The sole vaccine group offering protection for BKD was found to significantly decrease the hazard of dying (hazard ratio, HR = 0.68, P = 0.018) during the outbreak, compared to the industry standard, vaccine group. Additionally, during the outbreak, fish with a shortened operculum had a significantly decreased hazard (HR = 0.38, P = 0.033) compared to those fish with a normal operculum, while fish with jaw deformities had a significantly increased hazard (HR = 2.55, P = 0.001) compared to fish with normal jaw status.
Carl B. Schreck - One of the best experts on this subject based on the ideXlab platform.
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Effects of Bacterial Kidney Disease on saltwater preference of juvenile spring chinook salmon, Oncorhynchus tshawytscha
Aquaculture, 2003Co-Authors: Carol Seals Price, Carl B. SchreckAbstract:Abstract In March 1998, we conducted a laboratory experiment to assess the effect of Bacterial Kidney Disease (BKD) on the saltwater preference of juvenile spring chinook salmon, Oncorhynchus tshawytscha . Experiments were done in 757-l tanks in which a vertical salinity gradient was established. Fish with external signs of BKD were designated as sick and those without external signs of Disease served as controls. Two hours after saltwater introduction, 85±17.6% (S.D.) of controls held in salt water, compared to 31±20.0% of sick fish. There was a significant negative relationship between mean infection level (quantified by enzyme-linked immunosorbent assay, ELISA) and saltwater preference. Such behavior may increase the risk of avian predation for chinook salmon outmigrating through the estuary.
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Appetite of chinook salmon (Oncorhynchus tshawytscha) naturally infected with Bacterial Kidney Disease
Aquaculture, 2000Co-Authors: Juhani Pirhonen, Carl B. Schreck, Ann L. GannamAbstract:We evaluated the use of feed restriction to decrease mortality and infection rates in yearling chinook salmon (Oncorhynchus tshawytscha) naturally infected with Renibacterium salmoninarum, the causative agent of Bacterial Kidney Disease (BKD). Fish were purposely stressed and then fed either full ration, half ration, or fasted. At the termination of the 6-week experiment, feed intake of the fish was evaluated by X-radiography after feeding all groups in excess and the amount of BKD p57 antigen in the Kidneys was measured by enzyme linked immonosorbent assay (ELISA) to assess effects of infection on feeding rates. Only a few individuals in each treatment died during the experiment, but the proportion of fish with detectable antigen concentration increased as ration level decreased. Within each treatment, fish with undetectable concentrations of p57 antigen ate significantly more than fish with elevated antigen levels. Exponential regressions were fitted for each ration level describing the decrease of appetite as levels of antigen concentrations increased. The data indicate that even fish that were quite sick as judged from their relatively high antigen concentrations can still feed and that previous food shortage can increase the feed intake to some extent in the sick fish.
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Influence of Bacterial Kidney Disease on smoltification in salmonids: is it a case of double jeopardy?
Aquaculture, 1999Co-Authors: Matthew G Mesa, Alec G. Maule, Thomas P. Poe, Carl B. SchreckAbstract:Abstract We investigated the effects of a chronic, progressive infection with Renibacterium salmoninarum (Rs), the causative agent of Bacterial Kidney Disease (BKD), on selected aspects of smoltification in yearling juvenile spring chinook salmon (Oncorhynchus tshawytscha). After experimentally infecting fish with Rs using an immersion challenge, we sampled them every two weeks to monitor changes in gill Na+, K+-ATPase (ATPase), cortisol, infection level, mortality, growth, and other stress-related physiological factors during the normal time of parr–smolt transformation in fresh water (i.e., from winter to spring). A progressively worsening infection with Rs did not alter the normal changes in gill ATPase and condition factor associated with smoltification in juvenile chinook salmon. The infection did, however, lead to elevated levels of plasma cortisol and lactate and depressed levels of plasma glucose, indicating that the Disease is stressful during the later stages. A dramatic proliferation of BKD was associated with maximal responses of indicators of smoltification, suggesting that the process of smoltification itself can trigger outbreaks of Disease. Our results suggest mechanisms that probably influence the reported inability of Rs-infected fish to successfully adapt to sea water.
Ronald J. Pascho - One of the best experts on this subject based on the ideXlab platform.
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Decreased Mortality of Lake Michigan Chinook Salmon after Bacterial Kidney Disease Challenge: Evidence for Pathogen-Driven Selection?
Journal of aquatic animal health, 2008Co-Authors: Maureen K. Purcell, Ronald J. Pascho, Anthony L. Murray, Anna E. Elz, Linda K. Park, Susan V. Marcquenski, James R. Winton, Stewart W. Alcorn, Diane G. ElliottAbstract:Abstract In the late 1960s, Chinook salmon Oncorhynchus tshawytscha from the Green River, Washington, were successfully introduced into Lake Michigan. During spring from1988 to 1992, large fish die-offs affecting Chinook salmon occurred in the lake. Multiple ecological factors probably contributed to the severity of the fish kills, but the only Disease agent found regularly was Renibacterium salmoninarum, the causative agent of Bacterial Kidney Disease. In this study, survival after challenge by R. salmoninarum was compared between two Chinook salmon stocks: a Lake Michigan stock from Wisconsin (WI) and the progenitor stock from the Green River. We found that the WI stock had significantly greater survival than the Green River stock. Next, the WI and Green River stocks were exposed to the marine pathogen Listonella anguillarum (formerly Vibrio anguillarum), one of the causative agents of vibriosis; survival after this challenge was significantly poorer for the WI stock than for the Green River stock. A cl...
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Genetic effects of ELISA-based segregation for control of Bacterial Kidney Disease in Chinook salmon (Oncorhynchus tshawytscha)
Canadian Journal of Fisheries and Aquatic Sciences, 2006Co-Authors: Jeffrey J. Hard, Ronald J. Pascho, Diane G. Elliott, Dorothy M. Chase, Linda K. Park, James R. Winton, Donald E. CamptonAbstract:We evaluated genetic variation in ability of Chinook salmon (Oncorhynchus tshawytscha) to resist two bacte- rial pathogens: Renibacterium salmoninarum, the agent of Bacterial Kidney Disease (BKD), and Listonella anguillarum, an agent of vibriosis. After measuring R. salmoninarum antigen in 499 adults by enzyme-linked immunosorbent assay (ELISA), we mated each of 12 males with high or low antigen levels to two females with low to moderate levels and exposed subsets of their progeny to each pathogen separately. We found no correlation between R. salmoninarum anti- gen level in parents and survival of their progeny following pathogen exposure. We estimated high heritability for re- sistance to R. salmoninarum (survival h 2 = 0.890 ± 0.256 (mean ± standard error)) independent of parental antigen level, but low heritability for resistance to L. anguillarum (h 2 = 0.128 ± 0.078). The genetic correlation between these survivals (rA = -0.204 ± 0.309) was near zero. The genetic and phenotypic correlations between survival and antigen levels among surviving progeny exposed to R. salmoninarum were both negative (rA = -0.716 ± 0.140; rP = -0.378 ± 0.041), indicating that variation in antigen level is linked to survival. These results suggest that selective culling of female broodstock with high antigen titers, which is effective in controlling BKD in salmon hatcheries, will not affect resistance of their progeny.
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A cohabitation challenge to compare the efficacies of vaccines for Bacterial Kidney Disease (BKD) in chinook salmon Oncorhynchus tshawytscha.
Diseases of aquatic organisms, 2005Co-Authors: Stewart W. Alcorn, Ronald J. Pascho, Anthony L. Murray, Jed VarneyAbstract:The relative efficacies of 1 commercial and 5 experimental vaccines for Bacterial Kidney Disease (BKD) were compared through a cohabitation waterborne challenge. Groups of juvenile chinook salmon Oncorhynchus tshawytscha were vaccinated with one of the following: (1) killed Renibacterium salmoninarum ATCC 33209 (Rs 33209) cells; (2) killed Rs 33209 cells which had been heated to 37 degrees C for 48 h, a process that destroys the p57 protein; (3) killed R. salmoninarum MT239 (Rs MT239) cells; (4) heated Rs MT239 cells; (5) a recombinant version of the p57 protein (r-p57) emulsified in Freund's incomplete adjuvant (FIA); (6) the commercial BKD vaccine Renogen; (7) phosphate-buffered saline (PBS) emulsified with an equal volume of FIA; or (8) PBS alone. Following injection, each fish was marked with a subcutaneous fluorescent latex tag denoting its treatment group and the vaccinated fish were combined into sham and Disease challenge tanks. Two weeks after these fish were vaccinated, separate groups of fish were injected with either PBS or live R. salmoninarum GL64 and were placed inside coated-wire mesh cylinders (liveboxes) in the sham and Disease challenge tanks, respectively. Mortalities in both tanks were recorded for 285 d. Any mortalities among the livebox fish were replaced with an appropriate cohort (infected with R. salmoninarum or healthy) fish. None of the bacterins evaluated in this study induced protective immunity against the R. salmoninarum shed from the infected livebox fish. The percentage survival within the test groups in the R. salmoninarum challenge tank ranged from 59% (heated Rs MT239 bacterin) to 81% (PBS emulsified with FIA). There were no differences in the percentage survival among the PBS-, PBS/FIA-, r-p57- and Renogen-injected groups. There also were no differences in survival among the bacterin groups, regardless of whether the Bacterial cells had been heated or left untreated prior to injection.
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Comparison of Traditional and Molecular Methods for Detection of Renibacterium Salmoninarum
Reviews: Methods and Technologies in Fish Biology and Fisheries, 2002Co-Authors: Ronald J. Pascho, Diane G. Elliott, Dorothy M. ChaseAbstract:Bacterial Kidney Disease (BKD) caused by Renibacterium salmoninarum occurs in most parts of the world where wild or cultured salmonid fishes are present. Several extensive reviews have been written on the pathogen and the Disease (Fryer and Sanders, 1981; Austin and Austin, 1987; Elliott et al., 1989; Evelyn, 1993; Evenden et al., 1993; Fryer and Lannan, 1993). Bacterial Kidney Disease can cause serious mortality in juvenile salmonids in both fresh water and seawater, and also in prespawning adults. Although the chronic nature of the Disease has hindered accurate estimates of fish losses, particularly in feral fish populations, BKD is one the most important Bacterial Diseases affecting cultured salmonids, with reported losses as high as 80% in stocks of Pacific salmon (Oncorhynchus spp.) and 40% in stocks of Atlantic salmon (Salmo salar) (Evenden et al., 1993).
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Inactivation of Renibacterium salmoninarum by free chlorine
Aquaculture, 1995Co-Authors: Ronald J. Pascho, Marsha L. Landolt, Jerry E. OngerthAbstract:Abstract Salmonid fishes contract Bacterial Kidney Disease by vertical or horizontal transmission of the pathogenic bacterium, Renibacterium salmoninarum . Procedures to reduce vertical transmission are under evaluation, but methods are still needed to eliminate sources of waterborne R. salmoninarum . We examined the efficacy of chlorine to inactivate R. salmoninarum . The bacterium was exposed to various levels of chlorine at pH 6, 7, or 8, and at 7.5 °C or 15 °C. At pH 7 and 15 °C, 99% inactivation occurred within 18 s, even at free chlorine concentrations as low as 0.05 mg/l. Chlorine was most effective at neutral or acidic pH, and 15 °C. The inactivation curves for 7.5 °C and pH 7, or 15 °C and pH 8, deviated from first-order kinetics by exhibiting shoulders or a tailing-off effect, suggesting that chlorine and the Bacterial cells were not the sole reactants. A plot of the concentration-time ( Ct ) products for free chlorine at pH 7 and 15 °C produced a line with a slope less than 1, indicating that the duration of exposure was more important than the concentration of free chlorine. These data indicate that R. salmoninarum is very sensitive to chlorine, and that this disinfectant may be appropriate for use in fish hatcheries rearing salmonids affected by Bacterial Kidney Disease.
Alexander G. Murray - One of the best experts on this subject based on the ideXlab platform.
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Cost-effectiveness of alternative Disease management policies for Bacterial Kidney Disease in Atlantic salmon aquaculture
Aquaculture, 2014Co-Authors: Malcolm Hall, J. Soje, Rachel Kilburn, S. Maguire, Alexander G. MurrayAbstract:Bacterial Kidney Disease (BKD) is a systemic infectious disorder of the Salmonidae associated with increased mortality in Atlantic salmon a necessary cause of which is infection with Renibacterium salmoninarum. The cost-effectiveness of various possible national management policies to control this Disease is investigated. It is concluded that the control of BKD is cost-effective, and that a policy of limiting the spread of R. salmoninarum through the detection of BKD-affected sites, the imposition of movement restrictions on these, and the requirement to eradicate R. salmoninarum before movement restrictions are lifted, is economically more beneficial for this Disease than alternative policies of increased or reduced stringency.
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Implications of leaky boundaries for compartmentalised control of pathogens: A modelling case study for Bacterial Kidney Disease in Scottish salmon aquaculture
Ecological Modelling, 2013Co-Authors: Alexander G. MurrayAbstract:Compartmentalisation is the focusing of Disease control measures on valued and epidemiologically isolatable populations. However, pathogens may transmit across compartment boundaries and undermine local control measures. Bacterial Kidney Disease (BKD) affects both salmon and trout farms and a compartmentalised management programme has been adopted for Scotland with BKD more rigorously controlled in salmon farming regions. Undetected subclinical infection is an important uncertainty in BKD management. An existing epidemiological model has been adapted to assess the impact of external infection on the salmon compartment. The model has been modified to split infection pressure between exogenous (input) and endogenous (internal) spread, keeping the total infection pressure required to maintain the observed prevalence at steady-state. Model results suggest that BKD's persistence in salmon is dependent on input from trout or other external sources, even though these inputs are rare. Inputs also make it impossible to remove all risk of BKD occurring in salmon, although exclusion of BKD may be possible for long periods. BKD prevalence in salmon is likely to change in response to changes in other compartments, but any response will be less than linear. By far the largest predicted increases in BKD in Scottish salmon would occur if movement controls were to be lifted from salmon farms that are known to be infected. The model should have wider application to situations where pathogens are being eradicated from, or controlled within, specific compartments of multi-compartment systems and can be used to guide the appropriate balance between intensity of boundary and internal controls to minimise Disease occurrence in control compartments.
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Modelling management strategies for a Disease including undetected sub-clinical infection: Bacterial Kidney Disease in Scottish salmon and trout farms.
Epidemics, 2011Co-Authors: Alexander G. Murray, Malcolm Hall, Lorna A Munro, I Stuart WallaceAbstract:Disease is a major constraint on animal production and welfare in agriculture and aquaculture. Movement of animals between farms is one of the most significant routes of Disease transmission and is particularly hard to control for pathogens with subclinical infection. Renibacterium salmoninarum causes Bacterial Kidney Disease (BKD) in salmonid fish, but infection is often sub-clinical and may go undetected with major potential implications for Disease control programmes. A Susceptible-Infected model of R. salmoninarum in Scottish aquaculture has been developed that subdivides the infected phase between known and undetected sub-clinically infected farms and Diseased farms whose status is assumed to be known. Farms officially known to be infected are subject to movement controls restricting spread of infection. Model results are sensitive to prevalence of undetected infection, which is unknown. However, the modelling suggests that controls that reduce BKD prevalence include improve biosecurity on farms, including those not known to be infected, and improved detection of infection. Culling appears of little value for BKD control. BKD prevalence for rainbow trout farms is less sensitive to controls than it is for Atlantic salmon farms and so different management strategies may be required for the sectors.
Diane G. Elliott - One of the best experts on this subject based on the ideXlab platform.
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Genetic variation in Bacterial Kidney Disease (BKD) susceptibility in Lake Michigan Chinook Salmon and its progenitor population from the Puget Sound.
Journal of aquatic animal health, 2014Co-Authors: Maureen K. Purcell, Linda K. Park, James R. Winton, Jeffrey J. Hard, Kathleen G. Neely, Diane G. ElliottAbstract:AbstractMass mortality events in wild fish due to infectious Diseases are troubling, especially given the potential for long-term, population-level consequences. Evolutionary theory predicts that populations with sufficient genetic variation will adapt in response to pathogen pressure. Chinook Salmon Oncorhynchus tshawytscha were introduced into Lake Michigan in the late 1960s from a Washington State hatchery population. In the late 1980s, collapse of the forage base and nutritional stress in Lake Michigan were thought to contribute to die-offs of Chinook Salmon due to Bacterial Kidney Disease (BKD). Previously, we demonstrated that Lake Michigan Chinook Salmon from a Wisconsin hatchery have greater survival following BKD challenge relative to their progenitor population. Here, we evaluated whether the phenotypic divergence of these populations in BKD susceptibility was due to selection rather than genetic drift. Comparison of the overall magnitude of quantitative trait to neutral marker divergence betwee...
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Management of Bacterial Kidney Disease in Chinook Salmon Hatcheries Based on Broodstock Testing by Enzyme-Linked Immunosorbent Assay: A Multiyear Study
North American Journal of Fisheries Management, 2010Co-Authors: A. Douglas Munson, Diane G. Elliott, Keith A. JohnsonAbstract:Abstract From the mid-1980s through the early 1990s, outbreaks of Bacterial Kidney Disease (BKD) caused by Renibacterium salmoninarum continued in Chinook salmon Oncorhynchus tshawytscha in Idaho Department of Fish and Game (IDFG) hatcheries despite the use of three control methods: (1) injection of returning adult fish with erythromycin to reduce prespawning BKD mortality and limit vertical transmission of R. salmoninarum, (2) topical disinfection of green eggs with iodophor, and (3) prophylactic treatments of juvenile fish with erythromycin-medicated feed. In addition, programs to manage BKD through measurement of R. salmoninarum antigen levels in Kidney tissues from spawning female Chinook salmon by an enzyme-linked immunosorbent assay (ELISA) were tested over 13–15 brood years at three IDFG hatcheries. The ELISA results were used for either (1) segregated rearing of progeny from females with high ELISA optical density (OD) values (usually ≥0.25), which are indicative of high R. salmoninarum antigen le...
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Decreased Mortality of Lake Michigan Chinook Salmon after Bacterial Kidney Disease Challenge: Evidence for Pathogen-Driven Selection?
Journal of aquatic animal health, 2008Co-Authors: Maureen K. Purcell, Ronald J. Pascho, Anthony L. Murray, Anna E. Elz, Linda K. Park, Susan V. Marcquenski, James R. Winton, Stewart W. Alcorn, Diane G. ElliottAbstract:Abstract In the late 1960s, Chinook salmon Oncorhynchus tshawytscha from the Green River, Washington, were successfully introduced into Lake Michigan. During spring from1988 to 1992, large fish die-offs affecting Chinook salmon occurred in the lake. Multiple ecological factors probably contributed to the severity of the fish kills, but the only Disease agent found regularly was Renibacterium salmoninarum, the causative agent of Bacterial Kidney Disease. In this study, survival after challenge by R. salmoninarum was compared between two Chinook salmon stocks: a Lake Michigan stock from Wisconsin (WI) and the progenitor stock from the Green River. We found that the WI stock had significantly greater survival than the Green River stock. Next, the WI and Green River stocks were exposed to the marine pathogen Listonella anguillarum (formerly Vibrio anguillarum), one of the causative agents of vibriosis; survival after this challenge was significantly poorer for the WI stock than for the Green River stock. A cl...
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Genetic effects of ELISA-based segregation for control of Bacterial Kidney Disease in Chinook salmon (Oncorhynchus tshawytscha)
Canadian Journal of Fisheries and Aquatic Sciences, 2006Co-Authors: Jeffrey J. Hard, Ronald J. Pascho, Diane G. Elliott, Dorothy M. Chase, Linda K. Park, James R. Winton, Donald E. CamptonAbstract:We evaluated genetic variation in ability of Chinook salmon (Oncorhynchus tshawytscha) to resist two bacte- rial pathogens: Renibacterium salmoninarum, the agent of Bacterial Kidney Disease (BKD), and Listonella anguillarum, an agent of vibriosis. After measuring R. salmoninarum antigen in 499 adults by enzyme-linked immunosorbent assay (ELISA), we mated each of 12 males with high or low antigen levels to two females with low to moderate levels and exposed subsets of their progeny to each pathogen separately. We found no correlation between R. salmoninarum anti- gen level in parents and survival of their progeny following pathogen exposure. We estimated high heritability for re- sistance to R. salmoninarum (survival h 2 = 0.890 ± 0.256 (mean ± standard error)) independent of parental antigen level, but low heritability for resistance to L. anguillarum (h 2 = 0.128 ± 0.078). The genetic correlation between these survivals (rA = -0.204 ± 0.309) was near zero. The genetic and phenotypic correlations between survival and antigen levels among surviving progeny exposed to R. salmoninarum were both negative (rA = -0.716 ± 0.140; rP = -0.378 ± 0.041), indicating that variation in antigen level is linked to survival. These results suggest that selective culling of female broodstock with high antigen titers, which is effective in controlling BKD in salmon hatcheries, will not affect resistance of their progeny.
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Both msa genes in Renibacterium salmoninarum are needed for full virulence in Bacterial Kidney Disease.
Applied and environmental microbiology, 2006Co-Authors: Alison Coady, Diane G. Elliott, Anthony L. Murray, Linda D. RhodesAbstract:Renibacterium salmoninarum, a gram-positive diplococcobacillus that causes Bacterial Kidney Disease among salmon and trout, has two chromosomal loci encoding the major soluble antigen (msa) gene. Because the MSA protein is widely suspected to be an important virulence factor, we used insertion-duplication mutagenesis to generate disruptions of either the msa1 or msa2 gene. Surprisingly, expression of MSA protein in broth cultures appeared unaffected. However, the virulence of either mutant in juvenile chinook salmon (Oncorhynchus tshawytscha) by intraperitoneal challenge was severely attenuated, suggesting that disruption of the msa1 or msa2 gene affected in vivo expression.