Papers by Theodore Meyers
Journal of Invertebrate Pathology, May 1, 1991
Tanner crabs (Chionoecetes bairdi) from the Sullivan Island area of southeast Alaska were sampled... more Tanner crabs (Chionoecetes bairdi) from the Sullivan Island area of southeast Alaska were sampled for 1 year to determine the prevalence and intensity of the parasitic dinoflagellate which causes bitter crab disease (BCD). The prevalence and intensity of infection were the greatest in the summer, declined in the fall and winter, and increased again in the spring. A possible relationship between softer, newer shells and higher levels of parasitism was also observed. In vivo transmission studies in the laboratory suggested there are several morphologically different forms of the vegetative cell of the BCD dinoflagellate which occur prior to sporulation of the parasite. In addition, it appears that both the two spore types produced by the parasite are infectious by injection and that there is no ploidy difference between the two spore types and the vegetative cell, suggesting that the two spore types may not represent separate sexes. 8 FBI Academic PESS, IW.
Diseases of Aquatic Organisms, 1990
The distribution of bitter crab syndrome in southeast Alaskan Tanner crabs Chionoecetes bairdi wa... more The distribution of bitter crab syndrome in southeast Alaskan Tanner crabs Chionoecetes bairdi was determined from population surveys conducted by the Alaska Department of Fish and Game and commercial catch census data provided by seafood processors and fishermen. Both sources of data indicate the disease syndrome is widespread, affecting 1/3 of the total subdistricts fished during the 1988/1989 season. with the upper Lynn Canal areas having the highcst prevalenct?s (up to 95"/0). A conservative estimate of the total economic loss to fishermen due to rejected diseased crabs was about $220 500, representing 5 ' Yo of the total catch for the season. Disease prevalence in male and female crabs was nearly equal, with a significantly higher prevalence found in crabs of both sexes that have molted within the year (newshell). The latter finding was new information suggesting further considerations regarding the seasonality and transmission of the parasite. Increasing prevalences and spread of the disease syndrome to new areas is suggested by the commercial data but needs further verification from additional population surveys. Diseased crabs are known to have been introduced into some areas through improper disposal by processors and fishermen. Management of bitter crab syndrome may be possible by harvesting crabsearlier in the year when fewer crabs are severely parasitized and meats are more marketable. Promotion of increased public awareness of the disease syndrome and proper disposal of infected crabs are also necessary components in controlling dissemination of this parasite.
Journal of Wildlife Diseases, 1991
Comparative Susceptibilities of Salmonid Species in Alaska to Infectious Hematopoietic Necrosis Virus (IHNV) and North American Viral Hemorrhagic Septicemia Virus (VHSV)
Journal of Aquatic Animal Health, Mar 1, 1997
... THEODORE R. MEYERS Alaska Department ofFish and Game, Commercial Fisheries Management andDeve... more ... THEODORE R. MEYERS Alaska Department ofFish and Game, Commercial Fisheries Management andDevelopment Division Post Office Box 25526, Juneau, Alaska 99802, USA ... Journal of Fish Diseases 10:309-313. Hetrick, E M., JL Fryer, and MD Knittel. 1979. ...
Journal of Fish Diseases, Nov 1, 1986
Viral erythrocytic necrosis (VEN) has been associated with large epizootics and high mortality in... more Viral erythrocytic necrosis (VEN) has been associated with large epizootics and high mortality in Pacific herring, Clupea harengus pallasi (Valenciennes), from two different locations in south-eastern Alaska, USA. Clinical signs of disease included whirling, pale gills, watery colourless blood, discoloured livers, pathognomonic magenta erythrocytic inclusion bodies and histopathological changes consistent with other infectious haemolytic anaemias in higher aninials. Transmission electron microscopy confirmed the presence of iridovirus-type particles associated with the cytoplasmic erythrocytic inclusion bodies. Other apparently healthy herring of various age classes from four additional areas in south-east Alaska also had clinical signs of VEN suggesting a wide distribution of the virus in Alaskan Pacific herring populations. Evidence regarding the two herring epizootics indicated that osmoregulatory stress may have precipitated mortalities in fish having severe anaemia caused by the VEN virus. This is the first reported occurrence of VEN in Alaska and the first natural epizootic known to be associated with the disease.
Diseases of Aquatic Organisms, 1999
Thousands of dead Pacific herring Clupea pallasi, Pacific hake Merluccius productus and walleye p... more Thousands of dead Pacific herring Clupea pallasi, Pacific hake Merluccius productus and walleye pollock Theragra chalcogramma were reported in Lisianski Inlet near Pelican, Alaska, USA, on August 1, 1998. The Pacific hake and pollock continued to die through the end of September. Virological examinations of dead fish identified the North American strain of viral hemorrhagic septicemia virus (VHSV) from all 3 species of fish as well as associated high virus titers and possible histopathological lesions. No other primary fish pathogens were detected and there were no apparent environmental causes for fish mortality. This is the first report of VHSV in 2 new Alaskan fish host species and of a natural epizootic associated with VHSV in which progressive mass mortality was observed simultaneously in herring and 2 other species of free-ranging marine fish.
Diseases of Aquatic Organisms, 1994
g h t n e r * , Rita M. ~e d r n a n ~ ' ~l a s k a Department of Fish and Game, Commercial Fishe... more g h t n e r * , Rita M. ~e d r n a n ~ ' ~l a s k a Department of Fish and Game, Commercial Fisheries Management and Development Division,
Diseases of Aquatic Organisms, 1993
Comparison of the enzyme-linked immunosorbent assay (ELISA) and the fluorescent antibody test (FA... more Comparison of the enzyme-linked immunosorbent assay (ELISA) and the fluorescent antibody test (FAT) for measuring the prevalences and levels of Renibacterium salmoninarum in wild and hatchery stocks of salmonid fishes in Alaska, USA
Journal of General Virology, Feb 1, 1987
The morphological, biochemical and growth characteristics of four members of the Reoviridae, thre... more The morphological, biochemical and growth characteristics of four members of the Reoviridae, three from the fish hosts, golden shiner (Notemigonus crysoleucas), chum salmon (Oncorhynchus keta) and channel catfish (Ictalurus punetatus) and one from American oyster (Crassostrea virginica), were compared. Electron microscopy of negatively stained virions revealed icosahedral particles approximately 75 nm in diameter composed of a double capsid. Complete particles had buoyant densities in CsC1 of 1.34 to 1.36 g/ml. The viruses replicated well in several fish cell lines, forming plaque-like syncytia in monolayer cultures. Each virus could be distinguished by the range of cell lines supporting its growth. Polyacrylamide gel electrophoresis showed that the genome of each virus was composed of 11 segments of dsRNA distributed among three size classes. There were three large, three medium and five small segments in each genome and each isolate had a unique electropherotype. The segments ranged from 2.5 × 10 6 to 0"31 X 106 mol. wt. with a total genome of approximately 15 × 10 6 mol. wt. Analysis by SDS-PAGE revealed that each virus had five major structural proteins. There were two large polypeptides of approximately 135 000 and 125 000 mol. wt., one medium size polypeptide of 70000 mol. wt. and two small polypeptides of 45000 and 34000 mol. wt. Of the major structural proteins, those of approximately 70000 and 34000 tool. wt. were consistently present in the highest concentrations. Minor virion proteins were detected but were not characterized. These four viruses, isolated from aquatic animals, were unlike viruses of the six established genera of the Reoviridae.
A Perspective: Molecular Detections of New Agents in Finfish—Interpreting Biological Significance for Fish Health Management
Journal of Aquatic Animal Health, May 17, 2022
The increased sensitivity of advanced molecular techniques greatly exceeds the sensitivities of t... more The increased sensitivity of advanced molecular techniques greatly exceeds the sensitivities of traditional detection methods for infectious agents. This sensitivity causes difficulty in interpreting the biological significance of such detections in fish (and shellfish), especially when the agent(s) cannot be cultured in the laboratory. In the Pacific Northwest, including Canada and Alaska, molecular detections of "new" (unknown or known but discovered in a different geographic location or fish host) potentially infectious agents in fish have received extensive media attention and misinterpretation that call for resource agencies to change current fish health surveillance practices or policies to include these agents. Fish health specialists from several of these agencies and organizations (see Acknowledgments) advise that any policy changes should be made only after further investigations to avoid wasting resources to conduct surveillance for organisms that are not significant to fish health or for non-infectious genetic material that does not represent a viable agent. Molecular detection is not proof of agent viability within or on host tissues and requires further investigation regarding the agent ability to replicate and evidence that the agent causes substantial risk of disease to exposed fish populations. This document provides examples of molecularly detected agents causing public concern that were accompanied by little or no data to provide context and assessment of biological significance, highlights important questions to be answered regarding these detections and provides a suggested pathway of investigative criteria to determine viability and pathogenicity of such agents that are necessary for consideration of any changes to aquatic animal health practices and policies.
Journal of Fish Diseases, Nov 21, 2017
This research was initiated in conjunction with a systematic, multiagency surveillance effort in ... more This research was initiated in conjunction with a systematic, multiagency surveillance effort in the United States (U.S.) in response to reported findings of infectious salmon anaemia virus (ISAV) RNA in British Columbia, Canada. In the systematic surveillance study reported in a companion paper, tissues from various salmonids taken from Washington and Alaska were surveyed for ISAV RNA using the U.S.-approved diagnostic method, and samples were released for use in this present study only after testing negative. Here, we tested a subset of these samples for ISAV RNA with three additional published molecular assays, as well as for RNA from salmonid alphavirus (SAV), piscine myocarditis virus (PMCV) and piscine orthoreovirus (PRV). All samples (n = 2,252; 121 stock cohorts) tested negative for RNA from ISAV, PMCV, and SAV. In contrast, there were 25 stock cohorts from Washington and Alaska that had one or more individuals test positive for PRV RNA; prevalence within stocks varied and ranged from 2% to 73%. The overall prevalence of PRV RNA-positive individuals across the study was 3.4% (77 of 2,252 fish tested). Findings of PRV RNA were most common in coho (Oncorhynchus kisutch Walbaum) and Chinook (O. tshawytscha Walbaum) salmon. K E Y W O R D S infectious salmon anaemia, piscine myocarditis virus, piscine orthoreovirus, reverse transcription real-time PCR, salmonid alphavirus, surveillance 1 | INTRODUCTION Many species of fish have been moved extensively around the globe for commercial and recreational purposes, sometimes resulting in the introduction or spread of important pathogens (Walker & Winton, 2010). Among salmonids, Myxobolus cerebralis (the causative agent of whirling disease) was introduced into North America from Europe (Hoffman, 1990), while infectious haematopoietic necrosis virus (IHNV) was introduced into Europe and Asia from North America
Diseases of Aquatic Organisms, 1992
Ulcerative slun tissues from 2 Pacific cod Gadus rnacrocephalus caught in Prince William Sound, A... more Ulcerative slun tissues from 2 Pacific cod Gadus rnacrocephalus caught in Prince William Sound, Alaska, USA, were examined for virus by Fish Pathology staff within the F.R.E.D. Division of the Alaska Department of Fish and Game. Six days after inoculation of Epitheliorna papulosum cyprini (EPC) cells at 14"C, diffuse rounding and lifting of cells from the monolayers suggestive of cytopathlc effect became visible in the lower sample dilutions. Ultrastructural examinations of affected EPC cells showed rhabdovirus particles within cytoplasmic vacuoles and on the cell surface membranes. Virus isolates from both cod were subsequently confirmed as viral hemorrhagic septicemia virus (VHSV) by serum neutralizabon and immunoblot assay. This is the first VHSV isolated from Pacific cod, which represents a new host species for the virus. Histologically, cod skin ulcers appeared to be caused by a foreign-body-type inflammatory response to foci of protozoa resembling X cells that also had plasmodial stages. Whether the rhabdovirus was incidental to the slun lesion or played a role in its etiology remains to be determined. The possible relationship between thls virus and the recent occurrences of VHSV in anadromous salmoruds from Washington State, USA, is discussed.
Diseases of Aquatic Organisms, Jun 29, 2007
Juvenile seawater-reared chinook salmon Oncorhynchus tshawytscha at a hatchery on Baranoff Island... more Juvenile seawater-reared chinook salmon Oncorhynchus tshawytscha at a hatchery on Baranoff Island, Alaska, USA, sustained chronic mortality associated with anemia and mixed infections by various obligate and opportunistic pathogens including a cytoplasmic erythrocytic virus resembling the agent of erythrocytic inclusion body syndrome (EIBS). This is the first case report of EIBS in Alaska and is a range extension of the disease.
Journal of Invertebrate Pathology, Mar 1, 1985
This report documents the incidence of parasitism in populations of the blue king crab, P. platyp... more This report documents the incidence of parasitism in populations of the blue king crab, P. platypus, by B. callosus in southeastern Alaska. From March 2 to 5, 1984, specimens of P. platypus were collected from Muir Inlet and Adams Inlet, Glacier Bay, Alaska, using commerical crabbing pots. Field measurements of each crab included determination of sex, wet weight to the nearest 2.5 g, width and length of carapace to the nearest 1 mm using Vernier calipers, carapace condition (D. A. Somerton and R. A.
Diseases of Aquatic Organisms, 1993
Diseases of Aquatic Organisms, 1989
Chronic losses in juvenile coho salmon at 2 Alaskan hatcheries were associated with neurologic d~... more Chronic losses in juvenile coho salmon at 2 Alaskan hatcheries were associated with neurologic d~sorders and with chronic myeloencephalitis of apparent bactenal etiology. The syndrome occurred as a sequela to bactenal coldwater disease, which also occurs in Alaska Thls case report appears to represent an extension of the geographic range of occurrence of the chronic neurologic form of coldwater disease, earlier cases of which have been reported In Washington and Oregon. Clinical signs are similar to whlrling d ~s e a s e and nutritional blacktail, both of which must be cons ~d e r e d in the differential diagnosis.
Journal of Fish Diseases, May 1, 1980
A viral agent (13p2), isolated from clinically normal juvenile American oysters {Crassostrea virg... more A viral agent (13p2), isolated from clinically normal juvenile American oysters {Crassostrea virginica) and characterized as a new serotype of reovirus, was tested to determine if it could replicate and produce disease in experimental juvenile oysters. Because the virus replicated well in the hluegill fry (BF-2) fish cell line, fingerling hluegills Lepomis macrochirus were included in the pathogenicity experiments. Exposure of oysters to the 13p2 virus in ambient seawater resulted in no significant mortality and no increased virus titres or histological lesions. Virus particles were not observed in tissues of exposed oysters when examined with transmission electron microscopy (TEM). Intraperitoneal inoculation of the 13p2 virus into bluegills resulted in 44% mortality associated with a focal necrotic hepatitis. Evidence of virus replication, when evaluated histologically or by virus titration, was observed in 94% of 32 inoculated fish. Samples of infected livers examined with TEM revealed typical cytoplasmic arrays of 13p2 virus particles in affected hepatocytes. Rising virus titres and hepatic lesions also occurred in bluegills exposed to water containing the 13p2 virus. These results indicated the natural host of the 13p2 virus was not the American oyster, but that it was a significant pathogen for at least one fish species.
Canadian Journal of Fisheries and Aquatic Sciences, Oct 1, 1998
Expression of subclinical viral infection in response to toxicant exposure has not previously bee... more Expression of subclinical viral infection in response to toxicant exposure has not previously been reported, but evidence presented herein indicates that activation of viral hemorrhagic septicemia virus (VHSV) may occur in Pacific herring (Clupea pallasi) exposed to crude oil encountered after an oil spill. Decreased incidence of hepatic inflammatory cells as a function of total polynuclear aromatic hydrocarbon (TPAH) concentration was evidence for immunosuppression in exposed fish, and decreased immune surveillance is a possible mechanism by which subclinical VHSV could be reactivated. Adult Pacific herring of unknown status regarding infection by VHSV were captured from the wild and exposed to weathered crude oil for 16-18 days. TPAH concentration in tissue, VHSV prevalence, and mortality were correlated with dose. Histopathologic lesions were significantly correlated with TPAH concentration and prevalence of VHSV, but not gender or length. Significant lesions included increased hepatocellular necrosis, splenic thrombosis, and decreased inflammation in the liver. Résumé : Les résultats présentés dans cet article indiquent qu'une exposition au pétrole brut survenant à la suite d'un déversement peut activer le virus responsable de la septicémie hémorragique virale (VSHV) chez le hareng du Pacifique (Clupea pallasi). Jamais auparavant l'expression d'une infection virale infraclinique causée par l'exposition à des substances toxiques n'avait été signalée dans la littérature. La réduction du nombre de cellules inflammatoires hépatiques en fonction de la concentration des hydrocarbures aromatiques polycycliques totaux (HAPT) dénotait la présence d'une immunosuppression chez les poissons exposés. La diminution de la surveillance immunitaire pourrait être un mécanisme favorisant la réactivation du virus et l'apparition d'une infection infraclinique à VSHV. Des harengs du Pacifique dont on ignorait le statut à l'égard de l'infection à VSHV ont été capturés en mer et exposés pendant 16 à 18 jours à du pétrole brut altéré. Une corrélation a été établie entre la concentration de HAPT dans les tissus, la prévalence du VSHV et la mortalité, d'une part, et la dose, d'autre part. Une corrélation significative a également été observée entre la présence de lésions histopathologiques, d'une part, et la concentration de HAPT et la prévalence du VSHV, d'autre part. Aucune corrélation n'a cependant été notée entre la présence de lésions histopathologiques et le sexe et la longueur des poissons. Les lésions importantes observées incluaient les pathologies suivantes : augmentation de la nécrose hépatocellulaire, thrombose splénique et réduction de l'inflammation dans le foie.
Black eye syndrome and a systemic rickettsia-like organism in Alaskan Chionoecetes spp. crabs, including normal eyestalk microanatomy
Diseases of Aquatic Organisms, Jul 28, 2022
A black eye syndrome (BES) was discovered in both captive and wild populations of Alaskan snow cr... more A black eye syndrome (BES) was discovered in both captive and wild populations of Alaskan snow crabs Chionoecetes opilio and Tanner crabs C. bairdi. Field prevalences ranged from 0.37% (n = 594/161295) to 19.6% (n = 62/316) in snow crabs from the eastern Bering Sea and from 0.09% (n = 15/16638) to 0.7% (n = 133/18473) in Tanner crabs from the same trawl samples, with a slightly greater percentage (1.4%, n = 57/3945) in Tanner crabs from the Aleutian and Kodiak islands fisheries in the Gulf of Alaska. BES is not associated with crab mortality and has 2 distinct manifestations: abnormal black foci of internal eye pigment with no discernible histological lesions, which, in many cases, is followed by corneal shell disease with ulceration and distal eyestalk erosion. It is assumed for this study that these are early and late stages of BES that are somehow related. Our results suggest that early stages of abnormal pigmentation are noninfectious, possibly related to changing ocean conditions affecting crab endocrinology and neuropeptide control of secondary eye pigment. Potential light-induced photoreceptor damage of harvested crabs with dark-adapted eyes is another anthropogenic factor possibly contributing to the early changes in eye pigmentation. Normal eyestalk microanatomy specific for Chionoecetes spp. is provided as necessary baseline information for future studies. Early in the study, an unreported rickettsia-like organism (RLO) was discovered infecting dissected black eyestalks submitted for examination from 5 of 6 dead snow crabs, suggesting association with BES. Subsequent samples indicated the RLO was systemic, infected both black and normal-appearing eyestalks, and was unrelated to BES. However, the multiorgan infection and histopathology indicated the RLO could be a primary pathogen of snow crabs.
Paramyxoviruses of Fish
Abstract The first fish paramyxovirus was isolated from normal adult Chinook salmon returning to ... more Abstract The first fish paramyxovirus was isolated from normal adult Chinook salmon returning to a coastal hatchery in Oregon in the fall of 1982. Subsequently, the virus was isolated from other stocks of adult Chinook salmon and one stock of adult coho salmon in California, Oregon, Washington and Alaska, leading to its designation as the Pacific salmon paramyxovirus (PSPV). The slow-growing virus can be isolated from tissues and ovarian fluids of healthy adult fish returning to spawn and apparently causes no clinical signs of disease or mortality. In 1995, a different and widely disseminated paramyxovirus was isolated from farmed Atlantic salmon in Norway and was designated as Atlantic salmon paramyxovirus (ASPV). Although this virus caused no disease or mortality when injected into juvenile Atlantic salmon, ASPV has been associated with proliferative gill inflammation in sea-reared yearling fish; however, additional infectious agents may be involved in the etiology of the condition. Sequence analysis of PSPV and ASPV isolates using the polymerase gene established their placement in the family Paramyxoviridae and has shown the two viruses to be closely related but sufficiently different from each other and from other known paramyxoviruses to possibly represent new genera within the family. The viruses can be diagnosed by isolation in cell culture with final confirmation by molecular methods. Other paramyxovirus-like agents have been observed or isolated from rainbow trout in Germany, from seabream in Japan associated with epithelial necrosis, from turbot in Spain associated with erythrocytic inclusion bodies and buccal/opercular hemorrhaging and from koi and common carp associated with gill necrosis in the European Union.
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Papers by Theodore Meyers