TABLE 5 - uploaded by Diane Elliott
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-Detection of Renibacterium salmoninarum by the direct fluorescent antibody test (DFAT) in kidney tissue smears from juvenile Rapid River Chinook salmon. See Table 4 for more information.
Source publication
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 prespawni...
Contexts in source publication
Context 1
... River Hatchery.-In the 7 years before ELISA-based BKD management was begun in BY 1993, R. salmoninarum was detected by DFAT in 4% of fish examined (Table 5). During the 4 years of high- BKD segregation, no R. salmoninarum was detected by DFAT in the low-negative groups reared at Rapid River Hatchery, whereas 17% of fish sampled in the high-BKD segregation groups reared at Clearwater Hatchery were R. salmoninarum positive by DFAT. ...
Citations
... Parameter 2 -Effectiveness of killing animals (at farm level or within the farm) for reducing/stopping the spread of the disease Culling of infected broodstock has proven to be efficient in reducing the prevalence of BKD in hatcheries (Munson et al., 2010;Faisal et al., 2012), decreasing the proportion of adult female Chinook salmon with R. salmoninarum positive test in the following generation from 56% to 85% (Munson et al., 2010). In Iceland, the culling of infected Atlantic salmon broodstock led to a decrease in the incidence of infection from 35% to less than 2% after a few years (Gu@mundsd ottir et al., 2000). ...
... Parameter 2 -Effectiveness of killing animals (at farm level or within the farm) for reducing/stopping the spread of the disease Culling of infected broodstock has proven to be efficient in reducing the prevalence of BKD in hatcheries (Munson et al., 2010;Faisal et al., 2012), decreasing the proportion of adult female Chinook salmon with R. salmoninarum positive test in the following generation from 56% to 85% (Munson et al., 2010). In Iceland, the culling of infected Atlantic salmon broodstock led to a decrease in the incidence of infection from 35% to less than 2% after a few years (Gu@mundsd ottir et al., 2000). ...
... Screening broodstock with test (ELISA) and culling of infected broodstock have been shown to be efficient in reducing the prevalence of BKD in hatcheries (Munson et al., 2010;Faisal et al., 2012), decreasing the proportion of adult female Chinook salmon with BKD positive test in the following generation by 56-85% (Munson et al., 2010). In Iceland, the culling of infected Atlantic salmon broodstock led to an important decrease in the incidence of infection from 35% to less than 2% after a few years (Gu∂mundsd ottir et al., 2000). ...
Bacterial kidney disease (BKD) was assessed according to the criteria of the Animal Health Law (AHL), in particular the criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as laid out in Article 9 and Article 8 for listing animal species related to BKD. The assessment was performed following the ad hoc method on data collection and assessment developed by AHAW Panel and already published. The outcome reported is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with an uncertain outcome. According to this assessment, BKD can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (66–90% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that BKD does not meet the criteria in Sections 1, 2 and 3 (Categories A, B and C; 1–5%, 33–66% and 33–66% probability of meeting the criteria, respectively) but meets the criteria in Sections 4 and 5 (Categories D and E; 66–90% and 66–90% probability of meeting the criteria, respectively). The animal species to be listed for BKD according to Article 8 criteria are provided.
... We chose to collect fry from the supplementation program to lessen the effects of removing more fish from the natural population and because of potential disease concerns from bringing fish in from the river. Bacterial kidney disease screening using enzyme-linked immunosorbent assay of kidney tissue from all females was performed (Munson et al. 2010), and progeny from the lowest optical density categories were used for the captive broodstock as bacterial kidney disease has been a large source of mortality in other captive broodstock programs . Priority of fry selection for the captive broodstock (in the following order) was given to NOR × NOR, NOR × HOR, and HOR × HOR matings from the supplementation program. ...
We examined the efficacy of a one‐generation (five brood years: 1997–2001) captive broodstock program for spring Chinook Salmon Oncorhynchus tshawytscha by comparing survival rates of captive broodstock progeny (CBP; F2) with that of hatchery‐origin fish (HOR) from a conservation hatchery supplementation program in which both groups were derived from the Tucannon River (Washington State) population for the 2000–2006 brood years. Survival rates compared were egg to fry, fry to smolt, egg to smolt, total (ages 3–5) and adult (ages 4+) smolt‐to‐adult‐return (SAR) survival, and total (ages 3–5) and adult (ages 4+) progeny‐to‐parent (P:P) ratio. Total escapement and adult P:P ratios were also examined to determine if observed demographic benefits to the population continued after the captive broodstock program ended. The CBP group had lower within‐hatchery survival than the HOR group, with significant differences in survival at the egg‐to‐fry and egg‐to‐smolt stages due to poor egg viability. Mean untransformed total and adult SARs for the CBP were half those of the HOR group; however, SARs did not differ significantly. The CBP also had significantly lower total and adult P:P ratios than the HOR group and were below replacement for six of the seven brood years. While the captive broodstock provided additional fish for release that would not have been available otherwise, overall the CBP performed poorly and below expectations compared with the HOR group, both within the hatchery and after release. The captive broodstock program provided a short‐term demographic boost, most notable in the 2008–2010 return years, but the benefit did not carry over after the program ended.
... Homogenized tissues were prepared to a 1:4 (w/v) dilution with PBS, 0.05% (v/v) Tween-20, and 0.01% (w/v) thimerosal. Following an established ELISA protocol , I used an affinity purified R. salmoninarum-goat antibody as a coating antibody (KPL, (Munson et al. 2010;. Like other studies, I set criteria to characterize antigen load levels ...
Renibacterium salmoninarum, the causative agent of bacterial kidney disease (BKD), is known to cause high mortality in both wild and cultured salmonids, causing concern for many of the salmonid populations. Bacterial kidney disease caused up to 80% mortality in cultured Pacific salmonids and 40% in Atlantic salmonids. Due to high mortality among salmonid species, the American Fisheries Society has defined R. salmoninarum as a regulated pathogen. Due to its regulated status, research efforts have focused on advancing fish health diagnostics and understanding the transmission of the bacteria. However, many of these studies focus on Pacific northwest salmonids and the understanding of R. salmoninarum dynamics is not well known among inland salmonids.
Aquaculture propagation of Greenback Cutthroat Trout (Oncorhynchus clarkii) is a necessary component of their management. Since their protection under the Endangered Species Act, broodstock of Greenback Cutthroat Trout have been established at Colorado Parks and Wildlife (CPW) hatcheries to allow more rapid reintroduction through stocking. In 2017, hatcheries rearing isolated strains of the Greenback Cutthroat Trout contributed 1.5 million eggs during the spawning season. However, one major constraint to maintaining spawning production of the Greenback is the spread of disease within a facility. Increased contact rates between fish in raceways may influence the transmission of a pathogen. To ensure fish health and promote best practices in fish culture, fish health inspections have served as a critical step in identifying prohibitive and regulated pathogens entering or exiting the hatchery systems.
Various diagnostic methods have been established to detect R. salmoninarum in salmonids. Culturing the bacteria is the most accurate and reliable assay for detection; however, it is a slow process and not suited for rapid assessment. Other methods used to detect R. salmoninarum include Direct Fluorescent Antibody Tests (DFAT), Polymerase Chain Reaction (PCR), and Enzyme-Linked Immunosorbent Assays (ELISA) and are typically performed using lethally collected kidney tissue. Currently, kidney tissues are used to screen for the presence of the bacteria using DFAT as the initial test and PCR as a confirmatory test, following the American Fisheries Fish (AFS) Health Blue Book protocol. The protocol was developed using highly susceptible Pacific northwest salmonids and it is unknown if the protocol is appropriate for testing inland salmonids which may be less susceptible. In addition, the current protocol requires sacrificing fish, which is undesirable in situations with valuable and sometimes irreplaceable broodstocks. Therefore, I examined the efficacy of the current AFS detection protocol and compared it to other potential approaches (Chapter 2). I also assessed several non- lethal approaches to detecting the bacteria (Chapter 1 and 2).
In chapter 1, I compared non-lethal sampling methods with standardized lethal kidney tissue sampling that is used to detect R. salmoninarum infections in salmonids. I collected anal, buccal, and mucus swabs (non-lethal qPCR) and kidney tissue samples (lethal DFAT) from 72 adult Brook Trout (Salvelinus fontinalis) reared at the Colorado Parks and Wildlife Pitkin Brood Unit and tested each sample to assess R. salmoninarum infections. Brook Trout were used as a model species for Cutthroat Trout because they are described as highly susceptible species. Standard kidney tissue detected R. salmoninarum 1.59 times more often than mucus swabs, compared to 10.43 and 13.16 times more often than buccal or anal swabs, respectively, indicating mucus swabs were the most effective and may be a useful non-lethal method. My study highlights the potential of non-lethal mucus swabs to sample for R. salmoninarum and suggests future studies are needed to refine this technique for use in aquaculture facilities and wild populations of inland salmonids.
In chapter 2, I assessed the probability of detecting the bacteria in several tissues using standard diagnostic tests. I collected three lethal tissue (kidney, liver, and spleen) and three nonlethal serum (blood, ovarian fluid, and mucus swabs) samples from 781 adult Greenback Cutthroat Trout at the Colorado Parks and Wildlife Poudre Rearing Unit. All tissues were tested for R. salmoninarum via DFAT and qPCR. The overall prevalence (all tissue types) of R. salmoninarum among the fish was 22.7% with DFAT and 81.8% with qPCR. Kidney and liver tissues resulted in the greatest number of detections using either assay. To calculate the probability of infection among kidney and liver tissues and probability of detection between assays, I developed a hierarchical occupancy model. The liver had the highest probability of infection among all fish (0.69) and the probability of detection within the liver was highest with qPCR (0.79). DFAT produced a high probability of false negative detections (0.58). Thus, I suggest that testing a combination of both kidney and liver tissues with qPCR may yield a higher detection rate that better predicts the probability of infection when performing fish health inspections.
Management of R. salmoninarum is particularly difficult because the bacterium utilizes both vertical and horizontal transmission. Vertical transmission occurs when infected brood fish transmit the bacterium to their eggs and ultimate their progeny. Previous studies suggest the bacterium cannot be paternally transmitted due to limited success of bacterial entry into the egg from the spermatozoa. Thus, vertical transmission is suggested to be maternal. Horizontal transmission occurs among individuals through the ingestion of contaminated fecal matter or through direct contact with infected fish or water. In previous studies, horizontal transmission has been suggested to contribute more toward infection persistence than vertical transmission in wild and hatchery fish populations. However, the relative importance of horizontal transmission in hatcheries, where flow-through systems may expose multiple fish lots, has received little attention. I conducted experiments to determine rates of vertical and horizontal transmission.
In chapter 3, I examined the potential for horizontal transmission among hatchery-reared brood fish at an R. salmoninarum-positive hatchery facility. Juvenile Cutthroat Trout were placed in sentinel cages near positive adult Rainbow Trout and Cutthroat Trout for three, 30-day periods during optimal temperatures for infection. After exposure, the caged Cutthroat Trout were euthanized, and kidney tissue was tested for R. salmoninarum with qPCR. Only one out of 360 potentially exposed fish tested positive. My data suggest that horizontal transmission may play a small role in maintaining infection in hatchery-reared inland trout. However, I also show that horizontal transmission can occur in a short time, an important consideration when moving fish both within a hatchery or from one unit to another.
In chapter 4, I assessed whether the bacterium is vertically transmitted in Cutthroat Trout from the Poudre Rearing Unit in Colorado and the rate of transmission from paternal and maternal brood fish. Adult brood fish were lethally tested for R. salmoninarum and stripped of gametes to create 32 families among four R. salmoninarum infection treatments (MNFN, MNFP, MPFN, MPFP; M: male, F: female, P: positive, N: negative). Progeny from each spawning treatment were sampled at 6- and 12-month post swim-up to test for the presence of R. salmoninarum with an enzyme-linked immunosorbent assay (ELISA) and quantitative
polymerase chain reaction (qPCR). My study indicates that vertical transmission occurs in inland Cutthroat trout and transmission is high when examined at the family level but is low within a family. These results suggest that hatcheries should limit vertical transmission through practices such as lethal culling, but also that adopting other methods such as testing eggs for R. salmoninarum should be considered in the future.
... However, a great deal of uncertainty about vertical transmission of the bacteria in inland salmonids and whether males can transmit the bacteria vertically remains. Previous studies have demonstrated higher prevalence of R. salmoninarum infections in progeny of heavily infected adult Chinook Salmon females (Pascho et al. 1991;Elliot et al. 1995;Munson et al 2010). Transmission of R. salmoninarum in inland Rainbow Trout progeny from infected adults has also been reported . ...
... Iodine is ineffective for disinfection of R. salmoninarum-infected ova (Evelyn et al. 1984). Preventive measures and slaughtering upon detection thus remain the only viable options available for mitigating the disease today, although a combination of these, together with administrating antibiotic injections to spawning adults, has resulted in some success in farming of Chinook salmon (Munson et al. 2010). ...
... The potential disease risks posed by hatchery stocks to free-ranging salmon is a topic of high concern, but there are relatively few examples demonstrating an effect (see Naish et al. 2007). In recent decades, using fish health approaches to control disease in hatcheries has been successful (Munson et al. 2010). Many freshwater salmon hatcheries rely on strict biosecurity-including a secure water supply-to prevent entry of pathogens from free-ranging fish in adjacent waters. ...
Chinook Salmon (Oncorhynchus tshawytscha) are increasingly vulnerable to anthropogenic activities and climate change, especially at their most southern species range in California’s Central Valley. There is considerable interest in understanding stressors that contribute to population decline and in identifying management actions that reduce the impacts of those stressors. Along the west coast of North America, disease has been linked to declining numbers of salmonids and identified as a key stressor resulting in mortality. In the Central Valley, targeted studies have revealed extremely high prevalence of infectious agents and disease. However, there has been insufficient monitoring to understand the effect that disease may have on salmon populations. In order to inform future research, monitoring, and management efforts, a two-day workshop on salmon disease was held at UC Davis on March 14-15, 2018. This paper summarizes the science presented at this workshop, including the current state of knowledge of salmonid disease in the Central Valley and current and emerging tools to better understand its impacts on salmon. We highlight case studies from other systems where successful monitoring programs have been implemented. First, in the Klamath River where the integration of several data collection and modeling approaches led to the development of successful management actions, and second in British Columbia where investment in researching novel technologies led to breakthroughs in the understanding of salmon disease dynamics. Finally, we identify key information and knowledge gaps necessary to guide research and management of disease in Central Valley salmon populations.
... The potential disease risks posed by hatchery stocks to free-ranging salmon is a topic of high concern, but there are relatively few examples demonstrating an effect (see Naish et al. 2007). In recent decades, using fish health approaches to control disease in hatcheries has been successful (Munson et al. 2010). Many freshwater salmon hatcheries rely on strict biosecurity-including a secure water supply-to prevent entry of pathogens from free-ranging fish in adjacent waters. ...
Chinook Salmon (Oncorhynchus tshawytscha)
are increasingly vulnerable to anthropogenic
activities and climate change, especially at
their most southern range in California’s
Central Valley. There is considerable
interest in understanding stressors that
contribute to population decline and in
identifying management actions that
reduce the effects of those stressors. Along
the west coast of North America, disease has been linked to declining numbers of
salmonids, and identified as a key stressor
that results in mortality. In the Central
Valley, targeted studies have revealed
extremely high prevalence of infectious
agents and disease. However, there has been
insufficient monitoring to understand the
effect that disease may have on salmon
populations. To inform future research,
monitoring, and management efforts, a
two-day workshop on salmon disease was held at the University of California, Davis
(UC Davis) on March 14-15, 2018. This paper
summarizes the science presented at this
workshop, including the current state of
knowledge of salmonid disease in the Central
Valley, and current and emerging tools to
better understand its effects on salmon. We
highlight case studies from other systems
where successful monitoring programs have
been implemented. First, in the Klamath
River where the integration of several datacollection
and modeling approaches led to
the development of successful management
actions, and second in British Columbia
where investment in researching novel
technologies led to breakthroughs in the
understanding of salmon disease dynamics.
Finally, we identify key information and
knowledge gaps necessary to guide research
and management of disease in Central Valley
salmon populations.
... The potential disease risks posed by hatchery stocks to free-ranging salmon is a topic of high concern, but there are relatively few examples demonstrating an effect (see Naish et al. 2007). In recent decades, using fish health approaches to control disease in hatcheries has been successful (Munson et al. 2010). Many freshwater salmon hatcheries rely on strict biosecurity-including a secure water supply-to prevent entry of pathogens from free-ranging fish in adjacent waters. ...
... Rs is an intracellular, gram-positive diplobacillus that can be transmitted both horizontally [2][3][4] and vertically [5,6]. The bacterium is known to attach to the flagellum of spermatozoa which is lost at egg fertilization [5][6][7][8], and eggs fertilized with milt-containing Rs have subsequently tested negative for Rs [6]. As such, vertical transmission is suspected to be primarily maternal, originating and developing through ovarian tissues [5,9]. ...
... Prior to injection, fish were anesthetized with tricane methanesulfonate (MS-222; Syndel; Ferndale, Washington) and sex was determined, if possible. Despite the lack of evidence that males contribute to the vertical transmission of Rs [5][6][7], both male and female brood fish were treated with Erymicin 200, in part because sex was difficult to ascertain, but also because the male contribution to vertical transmission in inland trout is unknown. All fish were weighed (average 2.0 kg) to allow administration of a standardized dose of 25 mg Erymicin 200 per kg of body weight, injected into the IP cavity through the midventral abdominal wall using a Socorex 5 cc self-refilling syringe (Socorex Isba SA; Ecublens) and 0.7 × 6 mm needle (Unimed; Lausanne). ...
Bacterial Kidney Disease, caused by Renibacterium salmoninarum (Rs), is widespread and can cause significant mortality at most life stages in infected salmonids. Rs is commonly found in inland trout, which can be carriers of the bacterium. Lethal spawns can be used to control vertical transmission to progeny through the culling of eggs from infected parents, but can be costly, time-consuming, and can negatively impact important and rare brood stocks. Erymicin 200 is an Investigational New Animal Drug (INAD) intended to reduce Rs levels in hatchery brood stocks and control vertical transmission to progeny. We tested the efficacy of Erymicin 200 injections in a positive, hatchery-resident rainbow trout (Oncorhynchus mykiss) brood stock in Colorado, USA. Brood fish age two and three were injected with 25 mg per kg of body weight Erymicin 200 three times prior to spawning. Erymicin 200 was effective in reducing Rs to below detectable levels in treated fish. However, both negative treated and control brood fish produced positive progeny, suggesting that Erymicin 200 did not prevent the vertical transmission of Rs.
... In recent years, the focus has shifted from treatment to brood segregation. Using enzyme-linked immunosorbent assays (ELISA) to detect RS in broodstock has allowed hatchery managers to segregate or eliminate progeny from females with active infections, and has resulted in a tangible decrease in RS infection (Hard et al. 2006;Munson et al. 2010;Faisal et al. 2012); however, RS prevalence remains variable by sex, species, location, and infection status with other, possibly synergistic bacteria (Loch et al. 2012). ...
Bacterial kidney disease (BKD), caused by Renibacterium salmoninarum (RS) is a chronic, often fatal disease of salmonid species, and can be particularly harmful to hatchery reared Chinook salmon (Oncorhynchus tshawytscha). Considerable research has focused on prevention of vertical and horizontal transmission; however, comparatively little research has investigated factors that increase prevalence of RS infection in captive environments. We evaluated the effects of three common hatchery conditions (handling, nutrition level, and rearing density), on RS infection prevalence. Fish were sampled at 30- and 60-days post-exposure to RS. Of 577 juveniles examined, 65 (11.27%) had anterior kidneys infected with RS. Using a logistic mixed model analysis, we found effects of nutrition level (P=0.018), handling (P=0.010) and sampling period (P=0.003) on the prevalence of RS. The interactions of nutrition and handling (P=0.008), and nutrition and time (P<0.001) were also significant. When fed a standard nutrition diet, proportionately fewer fish were infected with RS when not handled (7.16% vs 0.04%; P=0.003). Fish in the standard nutrition group also had a lower prevalence of RS during the second sampling period (4.08% vs 0.08%, respectively; P<0.001). When not handled, rearing with standard nutrition (11.50% vs 0.04%; P=0.004) resulted in a reduction in prevalence of RS infection. Additionally, non-handled fish had a much lower prevalence of RS infection during the second sampling period (2.66% vs 0.21%; P=0.009). While density did not affect prevalence of RS infection (P=0.145), fish reared at higher density had lower RS infection when not handled (16.48% vs 0.84%, p=0.004). For higher density fish, RS prevalence was lower during the second sampling period (10.57% vs 1.40%; P=0.002). Our results suggest that hatchery managers can reduce RS infection prevalence by maintaining an adequate nutritional regime as recommended by the manufacturer. Additionally, prevalence of RS may be reduced if managers decrease handling of hatchery-reared Chinook salmon if exposed to RS.
