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Paul K Hershberger - One of the best experts on this subject based on the ideXlab platform.
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Supplemental Material, Ichthyophonus_Suppl_Table_1 - Ichthyophonus sp. Infection in Opaleye (Girella nigricans)
2020Co-Authors: Elise E. B. Ladouceur, Jacob L Gregg, Maureen K. Purcell, Ashley Mackenzie, Judy St. Leger, Alexandria Mena, William N. Batts, Paul K HershbergerAbstract:Supplemental Material, Ichthyophonus_Suppl_Table_1 for Ichthyophonus sp. Infection in Opaleye (Girella nigricans) by Elise E. B. LaDouceur, Judy St Leger, Alexandria Mena, Ashley Mackenzie, Jacob Gregg, Maureen Purcell, William Batts and Paul Hershberger in Veterinary Pathology
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Ichthyophonus sp. Infection in Opaleye (Girella nigricans).
Veterinary pathology, 2020Co-Authors: Elise E. B. Ladouceur, Jacob L Gregg, Maureen K. Purcell, Ashley Mackenzie, Judy St. Leger, Alexandria Mena, William N. Batts, Paul K HershbergerAbstract:Over a 3-year-period, 17 wild-caught opaleye (Girella nigricans) housed in a public display aquarium were found dead without premonitory signs. Grossly, 4 animals had pinpoint brown or black foci on coelomic adipose tissue. Histologically, liver, spleen, heart, and posterior kidney had mesomycetozoan granulomas in all cases; other organs were less commonly infected. Four opaleye had goiter; additional substantial lesions were not identified. Granulomas surrounded melanized debris, leukocytes, and mesomycetozoa represented by folded membranes (collapsed schizont walls), intact schizonts (50- to >200 µm in diameter with a multilaminate membrane), plasmodia (budding from schizonts or free in tissue), or rarely germinal tubes (budding from schizonts). Ichthyophonus was grown from fresh tissues in tissue explant broth cultures of the heart, liver, and/or spleen. Polymerase chain reaction using 18S ribosomal DNA primers amplified a 1730-bp region, and the DNA sequence was most similar to Ichthyophonus hoferi, which is often associated with freshwater aquaculture fish.
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A geographic hot spot of Ichthyophonus infection in the southern Salish Sea, USA.
Diseases of aquatic organisms, 2019Co-Authors: Paul K Hershberger, Jacob L Gregg, Ashley Mackenzie, Adam Lindquist, T Sandell, Maya L. Groner, David LowryAbstract:The prevalence of Ichthyophonus infection in Pacific herring Clupea pallasii was spatially heterogeneous in the southern Salish Sea, Washington State, USA. Over the course of 13 mo, 2232 Pacific herring were sampled from 38 midwater trawls throughout the region. Fork length was positively correlated with Ichthyophonus infection at all sites. After controlling for the positive relationship between host size and Ichthyophonus infection, the probability of infection was approximately 6-fold higher in North Hood Canal than in Puget Sound and the northern Straits (12 vs. 2% predicted probability for a 100 mm fish and 30 vs. 7% predicted probability for a 180 mm fish). Temporal changes in Ichthyophonus infection probability were explained by seasonal differences in fish length, owing to Pacific herring life history and movement patterns. Reasons for the spatial heterogeneity remain uncertain but may be associated with density-dependent factors inherent to the boom-bust cycles that commonly occur in clupeid populations.
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Analytical and diagnostic performance of a qPCR assay for Ichthyophonus spp. compared to the tissue culture 'gold standard'.
Diseases of aquatic organisms, 2018Co-Authors: Vanessa C. Lowe, Paul K Hershberger, Carolyn S FriedmanAbstract:Parasites of the genus Ichthyophonus infect many fish species and have a non-uniform distribution within host tissues. Due in part to this uneven distribution, the comparative sensitivity and accuracy of using molecular-based detection methods versus culture to estimate parasite prevalence is under debate. We evaluated the analytical and diagnostic performance of an existing qPCR assay in comparison to the 'gold standard' culture method using Pacific herring Clupea pallasii with known exposure history. We determined that the assay is suitable for use in this host, and diagnostic specificity was consistently high (>98%) in both heart and liver tissues. Diagnostic sensitivity could not be fully assessed due to low infection rates, but our results suggest that qPCR is not as sensitive as culture under all circumstances. Diagnostic sensitivity of qPCR relative to culture is likely affected by the amount of sample processed. The prevalence values estimated by the 2 methods were not significantly different when sample amounts were equal (heart tissue), but when the assayed sample amounts were unequal (liver tissue), the culture method detected a significantly higher prevalence of the parasite than qPCR. Further, culture of liver also detected significantly more Ichthyophonus infections than culture of heart, suggesting that the density and distribution of parasites in tissues also plays a role in assay sensitivity. This sensitivity issue would be most problematic for fish with light infections. Although qPCR does not detect the presence of a live organism, DNA-based pathogen detection methods provide the opportunity for alternate testing strategies when culture is not possible.
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Ichthyophonus in sport-caught groundfishes from southcentral Alaska
Diseases of Aquatic Organisms, 2018Co-Authors: Bradley P Harris, Sarah R Webster, Jacob L Gregg, Nathan Wolf, Paul K HershbergerAbstract:This report of Ichthyophonus in common sport-caught fishes throughout the marine waters of southcentral Alaska represents the first documentation of natural Ichthyophonus infections in lingcod Ophiodon elongates and yelloweye rockfish Sebastes ruberrimus. In addition, the known geographic range of Ichthyophonus in black rockfish S. melanops has been expanded northward to include southcentral Alaska. Among all species surveyed, the infection prevalence was highest (35%, n = 334) in Pacific halibut Hippoglossus stenolepis. There were no gross indications of high-level infections or clinically diseased individuals. These results support the hypothesis that under typical conditions Ichthyophonus can occur at high infection prevalence accompanied with low-level infection among a variety of fishes throughout the eastern North Pacific Ocean, including southcentral Alaska.
Richard M. Kocan - One of the best experts on this subject based on the ideXlab platform.
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Transmission of a Freshwater Isolate of Ichthyophonus (Clade C) to Two Marine Fish Species.
Journal of aquatic animal health, 2019Co-Authors: Richard M. Kocan, A. J. Kocan, Stephen R. ReichleyAbstract:The ingestion of infected prey is the most recognizable mode of transmission for Ichthyophonus, but because this mode of transmission is unidirectional from small prey fish to larger predators, it cannot sustain the parasite within or among populations nor does it explain transmission to planktivores. Recently, waterborne transmission was demonstrated in cultured Rainbow Trout Oncorhynchus mykiss, which could explain how the parasite is transmitted without piscivory. However, it is possible that this is an adaptation to aquaculture conditions, and may not occur among wild fish. To address this question, experiments were conducted to determine if a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species, as well as if transmission is possible between different marine species. Pacific Staghorn Sculpins Leptocottus armatus were fed a freshwater isolate of Ichthyophonus (clade C) and then housed with susceptible sentinel Rock Soles Lepidopsetta bilineata. Ninety two percent of the orally exposed sculpins and 30% of the sentinel soles were Ichthyophonus-positive at the end of the study, with 0% infected controls. These results demonstrate that a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species and can be transmitted in seawater in the absence of piscivory. It also provides a plausible mechanism for transmission to small prey fish and planktivores, as well as within a population of piscivores when infected prey is not available.
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Transmission models for the fish pathogen Ichthyophonus: synthesis of field observations and empirical studies
Canadian Journal of Fisheries and Aquatic Sciences, 2019Co-Authors: Richard M. KocanAbstract:Empirical studies have demonstrated that Ichthyophonus is transmitted among piscivores via consumption of infected prey; however, this unidirectional mode of transmission from small to large fish cannot sustain Ichthyophonus within a population. To circumvent this problem, Ichthyophonus evolved an infective waterborne cell that has been shown to infect both fresh- and saltwater fish. Successful transmission of Ichthyophonus via a waterborne stage is linked to the proximity of infected and susceptible individuals, a condition met when the two groups occupy the same habitat. It is posited that this occurs during annual inshore migrations when herring (Clupea spp.) enter areas occupied by infected demersal predators. A plausible transmission scenario is that during inshore excursions, planktivores are exposed to infective waterborne cells shed by demersal piscivores. Once planktivores are infected, the parasite is recycled when consumed by predators. This model is supported by reports of ichthyophoniasis inc...
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Transmission models for the fish pathogen Ichthyophonus: Synthesis of field observations and empirical studies
Canadian Journal of Fisheries and Aquatic Sciences, 2019Co-Authors: Richard M. KocanAbstract:Empirical studies have demonstrated that Ichthyophonus is transmitted among piscivores via consumption of infected prey; however, this unidirectional mode of transmission from small to large fish c...
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Metamorphosis of Ichthyophonus Schizonts Transiting the Gastrointestinal Tract of Experimentally Exposed Rainbow Trout.
Journal of aquatic animal health, 2018Co-Authors: Richard M. Kocan, S E LapatraAbstract:Other than the initial infectious cell, schizonts are the only stage of the parasite Ichthyophonus sp. that has been identified in the tissues of a living host, and they are known to initiate new infections when ingested by a suitable host. However, after feeding Ichthyophonus-infected tissue to Rainbow Trout Oncorhynchus mykiss, we observed that once infection was initiated, some schizonts proceeded to develop into several other morphologic forms indistinguishable from those previously described from recently deceased hosts, decomposing infected corpses, and in vitro culture. It appeared that not all schizonts participated in the infection process; some initiated infection, as expected, while others passed into the intestines, where they morphed into multiple cell types (e.g., schizonts, some with partially digested or ruptured capsules, ameboid plasmodia, merozoites, hyphenated cells, and empty capsules). Some of these cells were viable when cultured, but none was infectious to naive Rainbow Trout when administered by gavage. We posit that (1) not all tissue schizonts are programmed to perform the same function or (2) not all respond similarly to their environment. After consumption by a piscivore, those schizonts that do not initiate an infection do not die but rather metamorphose into different cell types as they transit the gastrointestinal tract and are ultimately released back into the aquatic environment through defecation. The fate of these cells after exiting the host is presently unknown, but they likely represent a segment of the Ichthyophonus life cycle.
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Infected Donor Biomass and Active Feeding Increase Waterborne Transmission of Ichthyophonus sp. to Rainbow Trout Sentinels.
Journal of aquatic animal health, 2016Co-Authors: S E Lapatra, Richard M. KocanAbstract:AbstractThe precise nature of Ichthyophonus sp. transmission among wild fishes has eluded description for over a century. Transmission among piscivores is direct, via ingestion of infected prey, but there is also evidence for waterborne transmission between infected and uninfected individuals. Transmission among planktivores is believed to be via a waterborne infectious cell, but definitive proof of this mechanism has not been forthcoming. To explore possible mechanisms of transmission we used Rainbow Trout Oncorhynchus mykiss as a model system and examined the consequence of housing infected donor fish with uninfected (sentinel) fish, without physical contact. We examined two variables linked to transmission: (1) feeding and nonfeeding sentinel fish, and (2) biomass of infected donor fish. Specific-pathogen free sentinel trout were placed in fine-mesh baskets suspended in tanks containing varying numbers of larger Ichthyophonus-infected donor fish and held for 10 weeks, during which time they were examin...
James R. Winton - One of the best experts on this subject based on the ideXlab platform.
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Amplification and transport of an endemic fish disease by an introduced species
Biological Invasions, 2010Co-Authors: Paul K Hershberger, Jacob L Gregg, Bjorn K. Leeuw, Courtney A. Grady, Kenneth M. Lujan, Susan K. Gutenberger, Maureen K. Purcell, James C. Woodson, James R. Winton, Michael J. ParsleyAbstract:The introduction of American shad from the Atlantic to the Pacific coast of North America in the late 1800’s and the subsequent population expansion in the 1980’s resulted in the amplification of Ichthyophonus sp., a Mesomycetozoean parasite of wild marine fishes. Sequence analysis of the ribosomal DNA gene complex (small subunit and internal transcribed spacer regions) and Ichthyophonus epidemiological characteristics indicate a low probability that Ichthyophonus was co-introduced with American shad from the Atlantic; rather, Ichthyophonus was likely endemic to marine areas of the Pacific region and amplified by the expanding population of a highly susceptible host species. The migratory life history of shad resulted in the transport of amplified Ichthyophonus from its endemic region in the NE Pacific to the Columbia River watershed. An Ichthyophonus epizootic occurred among American shad in the Columbia River during 2007, when infection prevalence was 72%, and 57% of the infections were scored as moderate or heavy intensities. The epizootic occurred near the record peak of shad biomass in the Columbia River, and corresponded to an influx of 1,595 mt of infected shad tissues into the Columbia River. A high potential for parasite spillback and the establishment of a freshwater Ichthyophonus life cycle in the Columbia River results from currently elevated infection pressures, broad host range, plasticity in Ichthyophonus life history stages, and precedents for establishment of the parasite in other freshwater systems. The results raise questions regarding the risk for sympatric salmonids and the role of Ichthyophonus as a population-limiting factor affecting American shad in the Columbia River.
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Sequence analysis of the internal transcribed spacer (ITS) region reveals a novel clade of Ichthyophonus sp. from rainbow trout.
Diseases of aquatic organisms, 2010Co-Authors: Charlotte Rasmussen, Maureen K. Purcell, James R. Winton, Scott E. Lapatra, J. L. Gregg, Paul K HershbergerAbstract:The mesomycetozoean parasite Ichthyophonus hoferi is most commonly associated with marine fish hosts but also occurs in some components of the freshwater rainbow trout Oncorhynchus mykiss aquaculture industry in Idaho, USA. It is not certain how the parasite was introduced into rainbow trout culture, but it might have been associated with the historical practice of feeding raw, ground common carp Cyprinus carpio that were caught by commercial fisherman. Here, we report a major genetic division between west coast freshwater and marine isolates of Ichthyophonus hoferi. Sequence differences were not detected in 2 regions of the highly conserved small subunit (18S) rDNA gene; however, nucleotide variation was seen in internal transcribed spacer loci (ITS1 and ITS2), both within and among the isolates. Intra-isolate variation ranged from 2.4 to 7.6 nucleotides over a region consisting of approximately 740 bp. Majority consensus sequences from marine/anadromous hosts differed in only 0 to 3 nucleotides (99.6 to 100% nucleotide identity), while those derived from freshwater rainbow trout had no nucleotide substitutions relative to each other. However, the consensus sequences between isolates from freshwater rainbow trout and those from marine/anadromous hosts differed in 13 to 16 nucleotides (97.8 to 98.2% nucleotide identity).
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Effects of temperature on disease progression and swimming stamina in Ichthyophonus-infected rainbow trout, Oncorhynchus mykiss (Walbaum).
Journal of fish diseases, 2009Co-Authors: Richard M. Kocan, Paul K Hershberger, G Sanders, James R. WintonAbstract:Rainbow trout, Oncorhynchus mykiss, were infected with Ichthyophonus sp. and held at 10 � C, 15 � C and 20 � C for 28 days to monitor mortality and disease progression. Infected fish demonstrated more rapid onset of disease, higher parasite load, more severe host tissue reaction and reduced meanday-to-death at higher temperature. In a second experiment, Ichthyophonus-infected fish were reared at 15 � C for 16 weeks then subjected to forced swimming at 10 � C, 15 � C and 20 � C. Stamina improved significantly with increased temperature in uninfected fish; however, this was not observed for infected fish. The difference in performance between infected and uninfected fish became significant at 15 � C( P = 0.02) and highly significant at 20 � C( P = 0.005). These results have implications for changes in the ecology of fish diseases in the face of global warming and demonstrate the effects of higher temperature on the progression and severity of ichthyophoniasis as well as on swimming stamina, a critical fitness trait of salmonids. This study helps explain field observations showing the recent emergence of clinical ichthyophoniasis in Yukon River Chinook salmon later in their spawning migration when water temperatures were high, as well as the apparent failure of a substantial percentage of infected fish to successfully reach their natal spawning areas.
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Ichthyophonus-induced cardiac damage: a mechanism for reduced swimming stamina in salmonids.
Journal of fish diseases, 2006Co-Authors: Richard M. Kocan, James R. Winton, J. L. Gregg, Scott E. Lapatra, Paul K HershbergerAbstract:Swimming stamina, measured as time-to-fatigue, was reduced by approximately two-thirds in rainbow trout experimentally infected with Ichthyophonus. Intensity of Ichthyophonus infection was most severe in cardiac muscle but multiple organs were infected to a lesser extent. The mean heart weight of infected fish was 40% greater than that of uninfected fish, the result of parasite biomass, infiltration of immune cells and fibrotic (granuloma) tissue surrounding the parasite. Diminished swimming stamina is hypothesized to be due to cardiac failure resulting from the combination of parasite-damaged heart muscle and low myocardial oxygen supply during sustained aerobic exercise. Loss of stamina in Ichthyophonus-infected salmonids could explain the poor performance previously reported for wild Chinook and sockeye salmon stocks during their spawning migration.
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High Doses of Corticosteroid Suppress Resistance to Ichthyophonus in Starry Flounder
Journal of Aquatic Animal Health, 2004Co-Authors: James A. Perry, James R. Winton, Richard M. Kocan, Paul K HershbergerAbstract:Abstract Application of pharmacological doses of the corticosteroid dexamethasone phosphate to starry flounder Platichthys stellatus resulted in a predisposition to clinical ichthyophoniasis and a progression from latent Ichthyophonus infections to patent, histologically identifiable infections. Among Ichthyophonus-challenged starry flounder, the prevalences of clinical infections and histologically identifiable infections were significantly greater in two groups that received dexamethasone (100% and 31%, respectively) than in the respective control groups (8% and 0%). Proliferation of Ichthyophonus infections in corticosteroid-treated groups may have resulted from suppression of the cellular immune response that typically follows corticosteroid application; however, further studies are needed to determine whether these effects occur at lower, physiological concentrations of corticosteroids.
Ronald J. Smolowitz - One of the best experts on this subject based on the ideXlab platform.
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Prevalence and description of Ichthyophonus sp. in yellowtail flounder (Limanda ferruginea) from a seasonal survey on Georges Bank
Fisheries Research, 2017Co-Authors: Carl Huntsberger, Jillian R. Hamlin, Ronald J. SmolowitzAbstract:Abstract Ichthyophonus sp. is a ubiquitous parasite infecting numerous fish species. Ichthyophonus sp. infection of yellowtail flounder ( Limanda ferruginea ) was first identified in Canadian waters in 1968. Between 2012 and 2014, fifteen seasonal survey cruises by Coonamessett Farm Foundation, randomly sampled a total of 1325 fish for at-sea examination at fixed stations on the U.S. Georges Bank sea scallop fishing grounds. A subsample of yellowtail flounders were examined internally on board the ship and animals with visible lesions were collected, processed, and examined histologically. Infected fish were concentrated in eastern Georges Bank with only two of the 32 infections collected from western Georges Bank. Both macroscopic and histological evaluation of tissues showed that 81.3% of the animals infected with Ichthyophonus sp. were severely infected.
Simon R. M. Jones - One of the best experts on this subject based on the ideXlab platform.
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ribosomal dna sequences indicate isolated populations of Ichthyophonus hoferi in geographic sympatry in the north eastern pacific ocean
Journal of Fish Diseases, 2002Co-Authors: Charles D. Criscione, Simon R. M. Jones, Virginia Watral, Christopher M. Whipps, Michael S. Blouin, Michael L. KentAbstract:Infections of Ichthyophonus hoferi, a cosmopolitan parasite of marine fish, have recently been reported in rockfish, Sebastes spp., from the north-eastern Pacific. Because I. hoferi also infects Pacific herring, Clupea pallasi Valenciennes, and salmonids in this region, we wanted to determine if Ichthyophonus parasites from rockfishes, Pacific herring and chinook salmon, Oncorhynchus tshawytscha (Walbaum), were the same. Small subunit ribosomal deoxyribonucleic acid sequence data revealed two haplotypes that were fixed among host species in geographic sympatry, one from rockfish and the other from both Pacific herring and salmon. These isolated populations of Ichthyophonus could be part of the same species that are ecologically separated because of host behaviours, or they could be distinct species that are host specific. Dietary patterns of the hosts indicate that ecological separation among hosts is possible, but the presence of distinct species may better explain the observed Ichthyophonus haplotype association with host species.
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Ichthyophonus hoferi plehn mulsow in british columbia stocks of pacific herring clupea pallasi valenciennes and its infectivity to chinook salmon oncorhynchus tshawytscha walbaum
Journal of Fish Diseases, 2002Co-Authors: Simon R. M. Jones, Sheila DaweAbstract:Pacific herring, Clupea pallasi Valenciennes, collected from three areas of coastal British Columbia were screened for Ichthyophonus by histological examination. The infectivity of Ichthyophonus to juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum), was examined in laboratory studies. Ichthyophonus was detected in a total of 82 of 356 herring from all three areas. Prevalence in 2000 and 2001 ranged from 10.5 to 52.5% and was significantly lower in more northern (Hecate Strait) samples. Ichthyophonus was detected by histological examination in chinook salmon following oral or intraperitoneal (i.p.) exposure to homogenates of infected herring tissue. Infections in Yukon stock chinook salmon were occasionally associated with mortality and with inflammation in all tissues examined. Infections were detected significantly more frequently in the caecal mesenteries of i.p.-infected compared with oral-infected chinook salmon. The distribution and prevalence of Ichthyophonus isolates among diverse host species may assist in stock identification and in an improved understanding of trophic interactions.
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Ichthyophonus hoferi Plehn & Mulsow in British Columbia stocks of Pacific herring, Clupea pallasi Valenciennes, and its infectivity to chinook salmon, Oncorhynchus tshawytscha (Walbaum)
Journal of Fish Diseases, 2002Co-Authors: Simon R. M. Jones, Sheila DaweAbstract:Pacific herring, Clupea pallasi Valenciennes, collected from three areas of coastal British Columbia were screened for Ichthyophonus by histological examination. The infectivity of Ichthyophonus to juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum), was examined in laboratory studies. Ichthyophonus was detected in a total of 82 of 356 herring from all three areas. Prevalence in 2000 and 2001 ranged from 10.5 to 52.5% and was significantly lower in more northern (Hecate Strait) samples. Ichthyophonus was detected by histological examination in chinook salmon following oral or intraperitoneal (i.p.) exposure to homogenates of infected herring tissue. Infections in Yukon stock chinook salmon were occasionally associated with mortality and with inflammation in all tissues examined. Infections were detected significantly more frequently in the caecal mesenteries of i.p.-infected compared with oral-infected chinook salmon. The distribution and prevalence of Ichthyophonus isolates among diverse host species may assist in stock identification and in an improved understanding of trophic interactions.
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Ribosomal DNA sequences indicate isolated populations of Ichthyophonus hoferi in geographic sympatry in the north‐eastern Pacific Ocean
Journal of Fish Diseases, 2002Co-Authors: Charles D. Criscione, Simon R. M. Jones, Virginia Watral, Christopher M. Whipps, Michael S. Blouin, Michael L. KentAbstract:Infections of Ichthyophonus hoferi, a cosmopolitan parasite of marine fish, have recently been reported in rockfish, Sebastes spp., from the north-eastern Pacific. Because I. hoferi also infects Pacific herring, Clupea pallasi Valenciennes, and salmonids in this region, we wanted to determine if Ichthyophonus parasites from rockfishes, Pacific herring and chinook salmon, Oncorhynchus tshawytscha (Walbaum), were the same. Small subunit ribosomal deoxyribonucleic acid sequence data revealed two haplotypes that were fixed among host species in geographic sympatry, one from rockfish and the other from both Pacific herring and salmon. These isolated populations of Ichthyophonus could be part of the same species that are ecologically separated because of host behaviours, or they could be distinct species that are host specific. Dietary patterns of the hosts indicate that ecological separation among hosts is possible, but the presence of distinct species may better explain the observed Ichthyophonus haplotype association with host species.
