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• 1. [Article] An Investigation of Ceratomyxa shasta sporulation following death of its Chinook salmon host

  As pre-spawning mortality (PSM) in Chinook salmon in the Willamette River Valley becomes a more defined and examined area of study, more focus is granted to not only preserving the health of these fish, ...

  Citation × Citation Citation Abstract Copy Title: An Investigation of Ceratomyxa shasta sporulation following death of its Chinook salmon host Author: Soderlund, Krista M. As pre-spawning mortality (PSM) in Chinook salmon in the Willamette River Valley becomes a more defined and examined area of study, more focus is granted to not only preserving the health of these fish, but also expanding knowledge concerning various pathogens that utilize the salmon as hosts and may be associated with PSM. One such parasite, a myxozoan named Ceratomyxa shasta, has been known to be extremely detrimental to salmon health, yet little literature exists concerning what exactly happens to this parasite once the salmon die. This thesis briefly outlines the complexity regarding this parasite’s relationship with the Chinook salmon, offers some context to transmission dynamics, and explores a recent investigation conducted over the course of the 2013-2014 academic year to determine the capability of Ceratomyxa shasta to live, continue to develop, and sporulate following the death of one of its hosts, the Chinook salmon. Title: An Investigation of Ceratomyxa shasta sporulation following death of its Chinook salmon host Author: Soderlund, Krista M. As pre-spawning mortality (PSM) in Chinook salmon in the Willamette River Valley becomes a more defined and examined area of study, more focus is granted to not only preserving the health of these fish, but also expanding knowledge concerning various pathogens that utilize the salmon as hosts and may be associated with PSM. One such parasite, a myxozoan named Ceratomyxa shasta, has been known to be extremely detrimental to salmon health, yet little literature exists concerning what exactly happens to this parasite once the salmon die. This thesis briefly outlines the complexity regarding this parasite’s relationship with the Chinook salmon, offers some context to transmission dynamics, and explores a recent investigation conducted over the course of the 2013-2014 academic year to determine the capability of Ceratomyxa shasta to live, continue to develop, and sporulate following the death of one of its hosts, the Chinook salmon. Close

• 2. [Article] Modeling abiotic influences on disease dynamics for the complex life cycle of the myxozoan parasite Ceratomyxa shasta

  Most parasites and their hosts live in a balance within their environment; however a disease outbreak can occur when either the parasite, host, or environment, are perturbed. Myxozoan parasites are associated ...

  Citation × Citation Citation Abstract Copy Title: Modeling abiotic influences on disease dynamics for the complex life cycle of the myxozoan parasite Ceratomyxa shasta Author: Ray, Robert Adam Most parasites and their hosts live in a balance within their environment; however a disease outbreak can occur when either the parasite, host, or environment, are perturbed. Myxozoan parasites are associated with a wide variety of cultured and wild fish populations. Most myxozoans are relatively benign to their vertebrate host; however some cause dramatic population level effects on both cultured and wild fish populations. These parasites have a complex life cycle involving a vertebrate host (fish), an invertebrate host (annelid), and two spore stages (actinospore and myxospore). Interactions between these parasites and their hosts can be strongly influenced by environmental factors, most notably by water temperature and water velocity. Given the complex life cycle of myxozoan parasites and the lack of any chemical treatments or preventatives, controlling infections and disease caused by these parasites is challenging, especially for wild populations. The myxozoan Ceratomyxa shasta is endemic to many of the major rivers of the Pacific Northwest and infects all species of Pacific salmon. In the Klamath River, CA, USA, C. shasta infection is associated with decreased returns of adult Chinook salmon (Oncorhynchus tshawytscha). The goals of this dissertation were to 1) quantify the effect that elevated water temperature has on C. shasta-induced disease severity and mortality rate for both Chinook and coho (O. kitsch) salmon, 2) identify transmission patterns and quantify transmission rates of the actinospore stage to the salmon host, 3) develop an epidemiological model of this host-parasite life cycle and assess the sensitivity of specific parameters that may act as suitable management strategies, and 4) utilize a mixture cure model, an alternative survival analysis method, to quantify the effects water temperature and discharge on the total and rate of C. shasta-induced mortality of both Chinook and coho salmon. I found that, similar to disease progression naïve salmon species (i.e. from waters where C. shasta is absent), elevated water temperature increases the rate and overall mortality for salmon species from river systems where the parasite is endemic. Elevated water temperatures also increase the transmission rate of the actinospore stage to the salmon host. The transmission rate of the actinospore stage to the salmon host was inversely related to water velocity, and I identified a potential velocity threshold of ~0.3m/sec, above which transmission was greatly reduced. From the epidemiological model I sensitivity analyses and identified that reduction of the myxospore transmission rate from the adult salmon to the polychaete host during the winter may be the most effective management action to reduce C. shasta-related disease in the Klamath River. This action could potentially be achieved by increasing discharge during the winter to minimize contact between the polychaete host and myxospore stage. Lastly, I applied the mixture cure models to quantify how the daily survival rates of Chinook and coho salmon change over time after the fish become infected with C. shasta. Although varied in approach, the output from both of the models presented in this dissertation can be used to guide management and conservation actions for fish populations affected by myxozoan parasites. Title: Modeling abiotic influences on disease dynamics for the complex life cycle of the myxozoan parasite Ceratomyxa shasta Author: Ray, Robert Adam Most parasites and their hosts live in a balance within their environment; however a disease outbreak can occur when either the parasite, host, or environment, are perturbed. Myxozoan parasites are associated with a wide variety of cultured and wild fish populations. Most myxozoans are relatively benign to their vertebrate host; however some cause dramatic population level effects on both cultured and wild fish populations. These parasites have a complex life cycle involving a vertebrate host (fish), an invertebrate host (annelid), and two spore stages (actinospore and myxospore). Interactions between these parasites and their hosts can be strongly influenced by environmental factors, most notably by water temperature and water velocity. Given the complex life cycle of myxozoan parasites and the lack of any chemical treatments or preventatives, controlling infections and disease caused by these parasites is challenging, especially for wild populations. The myxozoan Ceratomyxa shasta is endemic to many of the major rivers of the Pacific Northwest and infects all species of Pacific salmon. In the Klamath River, CA, USA, C. shasta infection is associated with decreased returns of adult Chinook salmon (Oncorhynchus tshawytscha). The goals of this dissertation were to 1) quantify the effect that elevated water temperature has on C. shasta-induced disease severity and mortality rate for both Chinook and coho (O. kitsch) salmon, 2) identify transmission patterns and quantify transmission rates of the actinospore stage to the salmon host, 3) develop an epidemiological model of this host-parasite life cycle and assess the sensitivity of specific parameters that may act as suitable management strategies, and 4) utilize a mixture cure model, an alternative survival analysis method, to quantify the effects water temperature and discharge on the total and rate of C. shasta-induced mortality of both Chinook and coho salmon. I found that, similar to disease progression naïve salmon species (i.e. from waters where C. shasta is absent), elevated water temperature increases the rate and overall mortality for salmon species from river systems where the parasite is endemic. Elevated water temperatures also increase the transmission rate of the actinospore stage to the salmon host. The transmission rate of the actinospore stage to the salmon host was inversely related to water velocity, and I identified a potential velocity threshold of ~0.3m/sec, above which transmission was greatly reduced. From the epidemiological model I sensitivity analyses and identified that reduction of the myxospore transmission rate from the adult salmon to the polychaete host during the winter may be the most effective management action to reduce C. shasta-related disease in the Klamath River. This action could potentially be achieved by increasing discharge during the winter to minimize contact between the polychaete host and myxospore stage. Lastly, I applied the mixture cure models to quantify how the daily survival rates of Chinook and coho salmon change over time after the fish become infected with C. shasta. Although varied in approach, the output from both of the models presented in this dissertation can be used to guide management and conservation actions for fish populations affected by myxozoan parasites. Close

• 3. [Article] Mortality threshold for juvenile Chinook salmon (Oncorhynchus tshawytscha) in an epidemiological model of Ceratomyxa shasta

  The myxozoan parasite, Ceratomyxa shasta, is the most significant pathogen of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Klamath River, CA, USA. This parasite requires two hosts - a freshwater ...

  Citation × Citation Citation Abstract Copy Title: Mortality threshold for juvenile Chinook salmon (Oncorhynchus tshawytscha) in an epidemiological model of Ceratomyxa shasta Author: Ray, R. Adam The myxozoan parasite, Ceratomyxa shasta, is the most significant pathogen of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Klamath River, CA, USA. This parasite requires two hosts - a freshwater polychaete (Manayunkia speciosa) and a salmonid - to complete its life cycle. The complex life cycle and large geographic area where infection occurs make monitoring and managing the disease, ceratomyxosis, difficult. Epidemiological models are helpful tools to examine complex disease systems as they serve to identify parameters and rank their relative importance. A system of equations is used to derive the basic reproductive number (Ro) of the parasite. In this paper we present a model for ceratomyxosis induced mortality in Chinook salmon. The field experiments described herein quantify the mortality threshold (a critical parameter in the model), by exposing native Chinook salmon to C. shasta in the Klamath River. The average percent mortality that resulted from this challenge ranged from 2.5% to 98.5% over an exposure dose of 4.4 - 612 x 106 parasites. This study identified a non-linear mortality threshold for Iron Gate Hatchery (IGH) Chinook salmon that ranged from 5.6 - 9.9 x 104 total parasites. Below this threshold no mortality occurs, yet above it mortality dramatically increases. This threshold provides a target to reduce parasitism in emigrating juvenile Chinook salmon. Title: Mortality threshold for juvenile Chinook salmon (Oncorhynchus tshawytscha) in an epidemiological model of Ceratomyxa shasta Author: Ray, R. Adam The myxozoan parasite, Ceratomyxa shasta, is the most significant pathogen of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Klamath River, CA, USA. This parasite requires two hosts - a freshwater polychaete (Manayunkia speciosa) and a salmonid - to complete its life cycle. The complex life cycle and large geographic area where infection occurs make monitoring and managing the disease, ceratomyxosis, difficult. Epidemiological models are helpful tools to examine complex disease systems as they serve to identify parameters and rank their relative importance. A system of equations is used to derive the basic reproductive number (Ro) of the parasite. In this paper we present a model for ceratomyxosis induced mortality in Chinook salmon. The field experiments described herein quantify the mortality threshold (a critical parameter in the model), by exposing native Chinook salmon to C. shasta in the Klamath River. The average percent mortality that resulted from this challenge ranged from 2.5% to 98.5% over an exposure dose of 4.4 - 612 x 106 parasites. This study identified a non-linear mortality threshold for Iron Gate Hatchery (IGH) Chinook salmon that ranged from 5.6 - 9.9 x 104 total parasites. Below this threshold no mortality occurs, yet above it mortality dramatically increases. This threshold provides a target to reduce parasitism in emigrating juvenile Chinook salmon. Close

• 4. [Article] Re-examining Ceratomyxa shasta in the Pacific Northwest

  Ceratomyxa shasta infects salmonids in the Pacific Northwest (PNW) of North America, occasionally causing losses in wild and captive populations. Host-specific parasite genotypes (O, I, II, III) were previously ...

  Citation × Citation Citation Abstract Copy Title: Re-examining Ceratomyxa shasta in the Pacific Northwest Author: Stinson, Matthew Everett Tsuneo, 1982- Ceratomyxa shasta infects salmonids in the Pacific Northwest (PNW) of North America, occasionally causing losses in wild and captive populations. Host-specific parasite genotypes (O, I, II, III) were previously characterized molecularly using markers in the ribosomal DNA and phenotypically by type host in the Klamath River, CA/OR. This thesis sough to re-examine the composition of the parasite population elsewhere in the PNW and to further evaluate the host specificity of each genotype. I surveyed salmonids native to the PNW primarily from the Fraser, the Columbia and the Sacramento River basins. I also conducted sentinel studies on the Willamette and Deschutes Rivers that exposed native and non-native salmonids to parasite populations above and below migration barriers. These studies expanded upon the known host range of each genotype: O was specific to rainbow/steelhead (Oncorhynchus mykiss) and coastal cutthroat trout (O. clarkii); I was specific with Chinook salmon (O. tshawytscha); II was non-specific, being detected in six species, but predominating in coho (O. kitsuch), chum (O. keta), and pink (O. gorbuscha) salmon; and III was also non-specific infecting many native and non-native salmonids. Hosts infected with genotype III were considered “adequate” if myxospore development occurred, and included brook char (Salvelinus fontinalis), brown (Salmo trutta), rainbow, cutthroat, and steelhead trout; but Chinook, kokanee/sockeye (O. nerka) and Atlantic salmon (Salmon salar) were less suitable. The distribution, life history, and phylogenetic traits of each salmonid host are factors that potentially explain the host specificity and the spatial and temporal patterns of each genotype. Data collected in this thesis provide evidence that host-specific C. shasta coevolved with Pacific salmonids, adapting unique host-parasite relationships over time. Title: Re-examining Ceratomyxa shasta in the Pacific Northwest Author: Stinson, Matthew Everett Tsuneo, 1982- Ceratomyxa shasta infects salmonids in the Pacific Northwest (PNW) of North America, occasionally causing losses in wild and captive populations. Host-specific parasite genotypes (O, I, II, III) were previously characterized molecularly using markers in the ribosomal DNA and phenotypically by type host in the Klamath River, CA/OR. This thesis sough to re-examine the composition of the parasite population elsewhere in the PNW and to further evaluate the host specificity of each genotype. I surveyed salmonids native to the PNW primarily from the Fraser, the Columbia and the Sacramento River basins. I also conducted sentinel studies on the Willamette and Deschutes Rivers that exposed native and non-native salmonids to parasite populations above and below migration barriers. These studies expanded upon the known host range of each genotype: O was specific to rainbow/steelhead (Oncorhynchus mykiss) and coastal cutthroat trout (O. clarkii); I was specific with Chinook salmon (O. tshawytscha); II was non-specific, being detected in six species, but predominating in coho (O. kitsuch), chum (O. keta), and pink (O. gorbuscha) salmon; and III was also non-specific infecting many native and non-native salmonids. Hosts infected with genotype III were considered “adequate” if myxospore development occurred, and included brook char (Salvelinus fontinalis), brown (Salmo trutta), rainbow, cutthroat, and steelhead trout; but Chinook, kokanee/sockeye (O. nerka) and Atlantic salmon (Salmon salar) were less suitable. The distribution, life history, and phylogenetic traits of each salmonid host are factors that potentially explain the host specificity and the spatial and temporal patterns of each genotype. Data collected in this thesis provide evidence that host-specific C. shasta coevolved with Pacific salmonids, adapting unique host-parasite relationships over time. Close

• 5. [Article] Geographic distribution of Ceratomyxa shasta in the Columbia River basin and susceptibility of salmonid stocks

  Citation × Citation Citation Abstract Copy Title: Geographic distribution of Ceratomyxa shasta in the Columbia River basin and susceptibility of salmonid stocks Author: Hoffmaster, Jerri Lee Title: Geographic distribution of Ceratomyxa shasta in the Columbia River basin and susceptibility of salmonid stocks Author: Hoffmaster, Jerri Lee Close

• 6. [Article] Climate warming effects on the life cycle of the parasite Ceratomyxa shasta in salmon of the Pacific Northwest

  Aquatic ecosystems continue to be increasingly affected by climate warming. For salmonids in the Pacific Northwest of North America, increasing temperatures pose tighter thermal constraints on their habitat ...

  Citation × Citation Citation Abstract Copy Title: Climate warming effects on the life cycle of the parasite Ceratomyxa shasta in salmon of the Pacific Northwest Author: Chiaramonte, Luciano V. Aquatic ecosystems continue to be increasingly affected by climate warming. For salmonids in the Pacific Northwest of North America, increasing temperatures pose tighter thermal constraints on their habitat use as well as aspects of their individual performance, such as disease resistance. This thesis examines the effect of temperature on the phenology of the Ceratomyxa shasta life cycle, the effect of thermal refugia on disease risk in juvenile salmonids in the Klamath River, CA, and the spatial and temporal distribution of C. shasta in the Willamette River, OR. We developed a biological model that predicts an acceleration of the C. shasta life cycle development due to climate shifts in the Klamath River, resulting in more generations per year and earlier seasonal parasite occurrence. We showed that in early summer the Beaver Creek-Klamath River confluence provides juvenile Chinook and coho salmon an area of lower parasite doses and cooler temperatures than the main stem, thus lessening disease risk. By accelerating the development of C. shasta in its hosts, increasing temperatures will result in earlier parasite transmission to juvenile salmonids and a longer season of infectivity. These fish may find disease refuge at cold tributary inflows to the main stem of the Klamath River in early summer, further adding to the benefit of these important thermal habitats. To determine if similar disease patterns occur in other rivers with the parasite, we described spatial and temporal occurrence of C. shasta in the Willamette River. By collecting weekly water sampling at four sites over 28 months we characterize seasonal and annual differences of parasite abundance, which varies with weekly temperature. We also collected samples along the length of the main stem and its tributaries and identified spatial differences in C. shasta spore densities. Identification of spatial and temporal variation of C. shasta in the Willamette River provides a foundation for understanding future patterns of disease occurrence in this river where conservation of anadromous fisheries is also of concern. This thesis identifies likely responses of C. shasta to climate warming in the Klamath River, with useful application to other rivers in the Pacific Northwest. Title: Climate warming effects on the life cycle of the parasite Ceratomyxa shasta in salmon of the Pacific Northwest Author: Chiaramonte, Luciano V. Aquatic ecosystems continue to be increasingly affected by climate warming. For salmonids in the Pacific Northwest of North America, increasing temperatures pose tighter thermal constraints on their habitat use as well as aspects of their individual performance, such as disease resistance. This thesis examines the effect of temperature on the phenology of the Ceratomyxa shasta life cycle, the effect of thermal refugia on disease risk in juvenile salmonids in the Klamath River, CA, and the spatial and temporal distribution of C. shasta in the Willamette River, OR. We developed a biological model that predicts an acceleration of the C. shasta life cycle development due to climate shifts in the Klamath River, resulting in more generations per year and earlier seasonal parasite occurrence. We showed that in early summer the Beaver Creek-Klamath River confluence provides juvenile Chinook and coho salmon an area of lower parasite doses and cooler temperatures than the main stem, thus lessening disease risk. By accelerating the development of C. shasta in its hosts, increasing temperatures will result in earlier parasite transmission to juvenile salmonids and a longer season of infectivity. These fish may find disease refuge at cold tributary inflows to the main stem of the Klamath River in early summer, further adding to the benefit of these important thermal habitats. To determine if similar disease patterns occur in other rivers with the parasite, we described spatial and temporal occurrence of C. shasta in the Willamette River. By collecting weekly water sampling at four sites over 28 months we characterize seasonal and annual differences of parasite abundance, which varies with weekly temperature. We also collected samples along the length of the main stem and its tributaries and identified spatial differences in C. shasta spore densities. Identification of spatial and temporal variation of C. shasta in the Willamette River provides a foundation for understanding future patterns of disease occurrence in this river where conservation of anadromous fisheries is also of concern. This thesis identifies likely responses of C. shasta to climate warming in the Klamath River, with useful application to other rivers in the Pacific Northwest. Close

• 7. [Article] Occurrence of the protozoan parasite Ceratomyxa shasta among salmonid fishes in Oregon waters

  This project was initiated to determine the incidence, distribution and species of fish affected by Ceratomyxa shasta in Oregon waters. Returning adult Pacific salmon and steelhead trout were chosen for ...

  Citation × Citation Citation Abstract Copy Title: Occurrence of the protozoan parasite Ceratomyxa shasta among salmonid fishes in Oregon waters Author: Sanders, James Edward This project was initiated to determine the incidence, distribution and species of fish affected by Ceratomyxa shasta in Oregon waters. Returning adult Pacific salmon and steelhead trout were chosen for the survey because they were known to be susceptible to infection. The parasite was also believed to be an important cause of prespawning losses. All coho salmon samples obtained from the Columbia River basin contained individuals infected with Ceratomyxa shasta. The infection was greatest at the Bonneville and Sandy hatcheries, where approximately 75 percent of the fish examined were infected. The only coastal sample found to contain coho salmon infected with Ceratomyxa shasta was taken from the Nehalem River. Fish that reached the hatchery but died before the start of spawning operations were obtained from the Klaskanine and Sandy hatcheries. The incidence of Certaomyxa shasta infected fish in these samples was in both cases greater than in samples obtained during spawning. Spring chinook obtained from coastal river locations (Trask and Rock Creek hatcheries) were not infected with this parasite. Infected spring chinook were found in all Willamette River tributaries surveyed. The incidence was greatest (28 percent at Dexter Dam) in fish which had migrated the farthest distance up the river. Ceratomyxa shasta in dead fish obtained from the Dexter Dam holding pond was over twice that found in spawned fish from this location. The incidence and distribution of Ceratomyxa shasta in fall chinook salmon was different from that found in coho or spring chinook. The coastal sample obtained from the Trask Hatchery contained one infected individual. The Klaskanine River was the only tributary on the lower Columbia that contained infected fall chinook, eight percent of these fish were infected. The infection was much greater in fall chinook sampled at the Oxbow Hatchery (Snake River) than in fish obtained from sites on the lower Columbia River. Sixty-five percent (65%) of the fish from this hatchery were infected. The incidence of Ceratomyxa shasta in prespawning mortalities at the Oxbow Hatchery (Snake River) was identical to that found in adults killed at spawning. Samples of steelhead trout obtained from the Big Creek Hatchery and Pelton Dam contained fish infected with this disease. The number of spores per smear of infected steelhead tissue was low when compared to the number observed in smears from coho and spring chinook. No steelhead mortalities were obtained. The incidence of Ceratomyxa shasta in adult salmonids does not appear to be related to the sex of the animals. The disease incidence appears to be related to the distance and rate of migration. Infections in adult salmonids caused by Ceratomyxa shasta probably occur during the freshwater phase of their life cycle. Geographically, Ceratomyxa shasta is widely distributed throughout the survey area. The parasite was found in all areas of the Columbia River basin sampled. Coastal river systems found to contain infected fish were the Nehalem and possibly the Trask. The incidence of Ceratomyxa shasta in coastal rivers decreased progressively from the Columbia River southward. Title: Occurrence of the protozoan parasite Ceratomyxa shasta among salmonid fishes in Oregon waters Author: Sanders, James Edward This project was initiated to determine the incidence, distribution and species of fish affected by Ceratomyxa shasta in Oregon waters. Returning adult Pacific salmon and steelhead trout were chosen for the survey because they were known to be susceptible to infection. The parasite was also believed to be an important cause of prespawning losses. All coho salmon samples obtained from the Columbia River basin contained individuals infected with Ceratomyxa shasta. The infection was greatest at the Bonneville and Sandy hatcheries, where approximately 75 percent of the fish examined were infected. The only coastal sample found to contain coho salmon infected with Ceratomyxa shasta was taken from the Nehalem River. Fish that reached the hatchery but died before the start of spawning operations were obtained from the Klaskanine and Sandy hatcheries. The incidence of Certaomyxa shasta infected fish in these samples was in both cases greater than in samples obtained during spawning. Spring chinook obtained from coastal river locations (Trask and Rock Creek hatcheries) were not infected with this parasite. Infected spring chinook were found in all Willamette River tributaries surveyed. The incidence was greatest (28 percent at Dexter Dam) in fish which had migrated the farthest distance up the river. Ceratomyxa shasta in dead fish obtained from the Dexter Dam holding pond was over twice that found in spawned fish from this location. The incidence and distribution of Ceratomyxa shasta in fall chinook salmon was different from that found in coho or spring chinook. The coastal sample obtained from the Trask Hatchery contained one infected individual. The Klaskanine River was the only tributary on the lower Columbia that contained infected fall chinook, eight percent of these fish were infected. The infection was much greater in fall chinook sampled at the Oxbow Hatchery (Snake River) than in fish obtained from sites on the lower Columbia River. Sixty-five percent (65%) of the fish from this hatchery were infected. The incidence of Ceratomyxa shasta in prespawning mortalities at the Oxbow Hatchery (Snake River) was identical to that found in adults killed at spawning. Samples of steelhead trout obtained from the Big Creek Hatchery and Pelton Dam contained fish infected with this disease. The number of spores per smear of infected steelhead tissue was low when compared to the number observed in smears from coho and spring chinook. No steelhead mortalities were obtained. The incidence of Ceratomyxa shasta in adult salmonids does not appear to be related to the sex of the animals. The disease incidence appears to be related to the distance and rate of migration. Infections in adult salmonids caused by Ceratomyxa shasta probably occur during the freshwater phase of their life cycle. Geographically, Ceratomyxa shasta is widely distributed throughout the survey area. The parasite was found in all areas of the Columbia River basin sampled. Coastal river systems found to contain infected fish were the Nehalem and possibly the Trask. The incidence of Ceratomyxa shasta in coastal rivers decreased progressively from the Columbia River southward. Close

• 8. [Article] The effects of water velocity on the Ceratomyxa shasta infectious cycle

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the author(s) and published by John Wiley & Sons Ltd. The article can be found ...

  Citation × Citation Citation Abstract Copy Title: The effects of water velocity on the Ceratomyxa shasta infectious cycle Author: Bartholomew, Jerri L., Bjork, Sarah J. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the author(s) and published by John Wiley & Sons Ltd. The article can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-2761. Title: The effects of water velocity on the Ceratomyxa shasta infectious cycle Author: Bartholomew, Jerri L., Bjork, Sarah J. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the author(s) and published by John Wiley & Sons Ltd. The article can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-2761. Close

• 9. [Article] Factors affecting the Ceratomyxa shasta infectious cycle and transmission between polychaete and salmonid hosts

  Ceratomyxa shasta is a myxozoan parasite that infects salmonid fishes causing the disease ceratomyxosis that is characterized by severe hemorrhage and necrosis of the intestine and death of the fish host. ...

  Citation × Citation Citation Abstract Copy Title: Factors affecting the Ceratomyxa shasta infectious cycle and transmission between polychaete and salmonid hosts Author: Bjork, Sarah J. Ceratomyxa shasta is a myxozoan parasite that infects salmonid fishes causing the disease ceratomyxosis that is characterized by severe hemorrhage and necrosis of the intestine and death of the fish host. Ceratomyxa shasta is endemic to the Pacific Northwestern United States and Canada, where epizootics are reported for both wild and hatchery reared fish. Identification of factors affecting the infectious cycle of C. shasta is complicated by its obligate two host lifecycle. The parasite infects the fish as an actinospore and develops into a myxospore in the fish host. The myxospore infects the freshwater polychaete, Manayunkia speciosa where the actinospore develops. A system for maintaining and infecting M. speciosa in the laboratory was developed and a series of laboratory studies tested the effects of temperature on polychaete survival, actinospore release and longevity. Temperature did not affect polychaete survival, but actinospore release occurred earlier and in greater abundance at the higher temperature, whereas actinospore longevity and temperature had an inverse relationship. A laboratory flow experiment tested the effects of two flow rates on M. speciosa survival, infection prevalence and fish infection. Polychaetes had higher survival at the fast flow with low infection prevalences compared to polychaetes held in the slow flow treatment. Susceptible rainbow trout became infected when exposed to just 1 actinospore per fish. Fatal infections in these fish were documented at 5 actinospores per fish. Infection prevalence and mean day to death increased with increasing actinospore dose. Fish size did not affect the infective dose; however, parasite dilution did have an effect. Actinospores were labeled with a fluorescent stain and C. shasta attachment to the gills was identified. In situ hybridization of histological sections was used to locate the parasite as it migrated from the gill epithelium, to proliferation in the blood vessel, and migration to the intestine. Quantitative PCR was used to quantify the abundance of the parasite in the blood. When the infection of susceptible and Resistant Chinook salmon were compared, there were no differences in actinospore penetration into the gills but resistant Chinook salmon did eliminate parasites in the blood after 2 weeks and isolate parasites in foci of inflammation in the intestine. Resistant Chinook salmon more effectively regulated an immune response to infection, effectively cleared the parasite showed evidence of recovery after infection. The research presented here has been fundamental in performing C. shasta infection studies in the laboratory in the fish and polychaete hosts. It has greatly affected our understanding of host parasite interactions including the infective dose for rainbow trout and the recognition of the gills and blood as early sites of C. shasta infection. It has also revealed differences in fish host response to infection including the characterization of a recovery from C. shasta infection. Title: Factors affecting the Ceratomyxa shasta infectious cycle and transmission between polychaete and salmonid hosts Author: Bjork, Sarah J. Ceratomyxa shasta is a myxozoan parasite that infects salmonid fishes causing the disease ceratomyxosis that is characterized by severe hemorrhage and necrosis of the intestine and death of the fish host. Ceratomyxa shasta is endemic to the Pacific Northwestern United States and Canada, where epizootics are reported for both wild and hatchery reared fish. Identification of factors affecting the infectious cycle of C. shasta is complicated by its obligate two host lifecycle. The parasite infects the fish as an actinospore and develops into a myxospore in the fish host. The myxospore infects the freshwater polychaete, Manayunkia speciosa where the actinospore develops. A system for maintaining and infecting M. speciosa in the laboratory was developed and a series of laboratory studies tested the effects of temperature on polychaete survival, actinospore release and longevity. Temperature did not affect polychaete survival, but actinospore release occurred earlier and in greater abundance at the higher temperature, whereas actinospore longevity and temperature had an inverse relationship. A laboratory flow experiment tested the effects of two flow rates on M. speciosa survival, infection prevalence and fish infection. Polychaetes had higher survival at the fast flow with low infection prevalences compared to polychaetes held in the slow flow treatment. Susceptible rainbow trout became infected when exposed to just 1 actinospore per fish. Fatal infections in these fish were documented at 5 actinospores per fish. Infection prevalence and mean day to death increased with increasing actinospore dose. Fish size did not affect the infective dose; however, parasite dilution did have an effect. Actinospores were labeled with a fluorescent stain and C. shasta attachment to the gills was identified. In situ hybridization of histological sections was used to locate the parasite as it migrated from the gill epithelium, to proliferation in the blood vessel, and migration to the intestine. Quantitative PCR was used to quantify the abundance of the parasite in the blood. When the infection of susceptible and Resistant Chinook salmon were compared, there were no differences in actinospore penetration into the gills but resistant Chinook salmon did eliminate parasites in the blood after 2 weeks and isolate parasites in foci of inflammation in the intestine. Resistant Chinook salmon more effectively regulated an immune response to infection, effectively cleared the parasite showed evidence of recovery after infection. The research presented here has been fundamental in performing C. shasta infection studies in the laboratory in the fish and polychaete hosts. It has greatly affected our understanding of host parasite interactions including the infective dose for rainbow trout and the recognition of the gills and blood as early sites of C. shasta infection. It has also revealed differences in fish host response to infection including the characterization of a recovery from C. shasta infection. Close

• 10. [Article] Ceratomyxa shasta-related concerns for reintroduced anadromous salmonids into the Upper Klamath Basin, CA-OR, USA

  The myxozoan parasite of salmonids, Ceratomyxa shasta, is established throughout the Klamath River, CA-OR, with high parasite densities below the series of dams and above the dams (upper basin) in the ...

  Citation × Citation Citation Abstract Copy Title: Ceratomyxa shasta-related concerns for reintroduced anadromous salmonids into the Upper Klamath Basin, CA-OR, USA Author: Hurst, Charlene N. The myxozoan parasite of salmonids, Ceratomyxa shasta, is established throughout the Klamath River, CA-OR, with high parasite densities below the series of dams and above the dams (upper basin) in the northernmost tributary, the Williamson River (WMR). Two objectives were designed to address concerns about C. shasta effects on reintroduced anadromous salmonids in the upper basin. The first objective investigated parasite dynamics in the WMR and the second determined the virulence of parasite genotypes in allopatric and sympatric salmonid strains. Parasite density, distribution and genotype composition were assessed from water samples collected throughout the WMR and its tributaries. High parasite densities occurred in two sections of the WMR and the genotype associated with stocking of an allopatric strain of rainbow trout predominated. In laboratory cross-infection experiments, the stage of the parasite infective for fish of genotypes I and II (biotype IIR and IIC) were used in three separate trials to challenge four strains of salmonid; sympatric strains of Chinook (Oncorhynchus tswytshcha) and coho (O. kisutch) salmon and allopatric strains of Chinook salmon and rainbow trout (O. mykiss). Genotype I caused mortality in both Chinook strains, while mortality in the allopatric Chinook strain also occurred with IIR. Mortality of rainbow trout resulted from biotypes IIR and IIC, but mortality in coho only occurred with exposure to IIC. Thus, the parasite genotypes/biotypes that cause mortality in native Klamath River fish (i.e. I and IIC) were not present in the upper basin, but could become established and amplify as the stocking of allopatric rainbow trout illustrates. Title: Ceratomyxa shasta-related concerns for reintroduced anadromous salmonids into the Upper Klamath Basin, CA-OR, USA Author: Hurst, Charlene N. The myxozoan parasite of salmonids, Ceratomyxa shasta, is established throughout the Klamath River, CA-OR, with high parasite densities below the series of dams and above the dams (upper basin) in the northernmost tributary, the Williamson River (WMR). Two objectives were designed to address concerns about C. shasta effects on reintroduced anadromous salmonids in the upper basin. The first objective investigated parasite dynamics in the WMR and the second determined the virulence of parasite genotypes in allopatric and sympatric salmonid strains. Parasite density, distribution and genotype composition were assessed from water samples collected throughout the WMR and its tributaries. High parasite densities occurred in two sections of the WMR and the genotype associated with stocking of an allopatric strain of rainbow trout predominated. In laboratory cross-infection experiments, the stage of the parasite infective for fish of genotypes I and II (biotype IIR and IIC) were used in three separate trials to challenge four strains of salmonid; sympatric strains of Chinook (Oncorhynchus tswytshcha) and coho (O. kisutch) salmon and allopatric strains of Chinook salmon and rainbow trout (O. mykiss). Genotype I caused mortality in both Chinook strains, while mortality in the allopatric Chinook strain also occurred with IIR. Mortality of rainbow trout resulted from biotypes IIR and IIC, but mortality in coho only occurred with exposure to IIC. Thus, the parasite genotypes/biotypes that cause mortality in native Klamath River fish (i.e. I and IIC) were not present in the upper basin, but could become established and amplify as the stocking of allopatric rainbow trout illustrates. Close