Progress 10/01/02 to 09/30/07
Outputs
OUTPUTS: No new information to report. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
No new information to report.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
Whirling disease in salmon & trout: Experiment completed in July to determine if the parasite that causes whirling disease, Myxobolus cerebralis, can be transferred by angler's waders. The results indicated that both life stages of the parasite could be transferred to the alternate host by waders (the parasite reproduces in trout & salmon & then in tubifex worms). Although the likelihood of transfer in an individual event is low, given the high fishing pressure in some locations, this could be a significant mechanism for the transfer of the parasite among watersheds. We have also determined that waders that have been contaminated with either parasite stage can remain infectious for up to 8 hours on boots that had been held out of water and dried. No infection occurred after this period. In a second set of experiments we examined the ability of a single infected fish to transmit the parasite to worms, and the effects of worm population density and strain on the
transfer. We have found that a single infected trout could indeed transfer the pathogen to more than 90% of the worms, depending on the susceptibility of the strain of worm used. Intriguingly, there is an inverse correlation between worm density and infection rate. We are hypothesizing that this is because at limiting concentrations of parasite spores, fewer worms would have a greater chance of ingesting spores than if too many worms were present. However, even though a higher percentage of worms are infected at low densities, the absolute numbers of worms infected at higher densities and therefore release more parasite spores into the water. In a parallel experiment on a putatively resistant strain of worms after 5 months, no signs of infection are evident (compared to high infection in the other worm strains after 3 months). Experiments using San Miguel Sea loin virus as a surrogate for Nowalk virus to determine susceptibility to high pressure post harvest processing were completed
early in the year. It was determined thar virus in culture medium is inactivated by at least 5 log by 2 mintues pressure at 376 MPa. The virus is readily ingested by oysters within minutes, but concentrated in superficial surfaces rather than within the hemocoele. Retention of the virus was transient, being cleared completely within 16 hours. Virus in oysters was inactivated to undetectable levels (>4 log) at 310 MPa for 2 minutes. Thus, high pressure processing conditions which have been found to inactivate Vibrio parahaemolyticus by greater than 5 logs were sufficient to inavtivate ocean origin caliciviruses to the same extent. This indicates a dual benefit for the use of high pressure processing in ridding bivalves of potential human pathogens.
Impacts
The emulation of the life cycle of Myxobolus cerebralis in the laboratory can lead to more efficacious and reliable evaluation of the factors that are associated with the establishment and maintenance of the parasite in aquaculture facilities and in wild salmonids. The extended length of the infectious period for the Tubifex worm, the production of prodigous numbers of TAMs, and the ability of a single infected worm or trout to infect the alternate host and cause disease is a fundimental piece of information needed to understand the ability of the parasite to become established in aquaculture facilities and in wild ecosystems. The ability of waders to serve as a mechanical vector of pathogen transmission will directly affect management practices in areas where the pathogen is present. The results of the seafood safety project indicate HHP is a viable method of postharvest processing that can significantly reduce the likelihood of consumers contracting gastroenteritis
from Norwalk-like agents in shellfish.
Publications
- Amogan, H.P., Martinez, J.P., Ciuffetti, L.M., Field, K.G. & Reno, P.W. 2006. Karyotype and genome size of Nadelspora canceri determined by pulsed field gel electrophoresis. Acta Protozoologica, 45:249-254.
- Koo, .J, Jahncke, M.L., Reno, P.W., Hu, X., Mallikarjunan, P. 2006. Inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in phosphate-buffered saline and in inoculated whole oysters by high-pressure processing. Journal of Food Protection, 69:596-601.
- Reno, P.W. 2006. The Effect of Infectious Diseases on Marine Populations. in Long Term Change in the Gulf of Alaska, R. Spies, Ed., Exxon Valdez Oil Spill Trustee Commission, pp. 128-152.
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Progress 01/01/05 to 12/31/05
Outputs
Fish Health: Experiments continued on the natural life cycle of Myxobolus cerebralis (Mc) in the laboratory. Carcasses of diseased rainbow trout (RBT) held upstream of Tubifex tubifex (Tt) infected the worms which then produced triactinomyxon spores (TAMs) after 80 d at up to 70% infection, with TAM outputs of 144-17,000/d. Nearly 3 years after the initial exposure (1065 d), 4/16 surviving Tt were still producing TAMs, (prevalence= 25%) at levels of between 30-1900 TAMs/d. This is considerably longer survival and higher TAM production than has been previously documented. Sentinel RBT placed downstream from the infected Tt were readily infected, even at exposure times as short as 1 minute; RBT exposed for 1 h or more exhibited clinical whirling disease at high levels. We have also determined that a single infected Tt can infect RBT and cause high levels of clinical whirling disease (75%), and that a single clinically diseased RBT (30 g) can infect susceptible Tt which
produce TAMs at levels of up to 33% and up to 9,000 TAM/d. In addition, in a study to determine the likelihood of transfer of the pathogen by anglers waders, we determined that both myxospores and TAMs can be transferred to their respective target hosts on waders, but inducing prevalences of less than 1%. The data generated in these experiments is being applied to constructing models for the dissemination of Mc in the rivers of eastern Oregon and other locations in MT, CO, NV, & PA. We are integrating the data obtained from these laboratory experiments with biotic and abiotic data from rivers harboring Mc infection to construct dynamic models of the disease process, especially integrating elements of worm life histories. Seafood Safety Project: The objectives of this work are to determine the optimum HPP operating parameters for inactivating caliciviruses as surrogates of Norwalk agent, and to determine whether the process will be commercially feasible. Virus uptake by immersion
reached saturation within 1 h then declined to undetectable levels within 16 h. Within the oyster, the majority of the virus was found in liquor and those tissues in contact with the exterior; little virus was found in hemolymph or adductor sinus. This indicates that the likelihood of oyster contamination is temporally limited to the proximity of a contaminating source of virus. High pressure processing of oysters immersed in SMSV-5 resulted in a > 5 log reduction in titer at 308 and 274 mPa in less than 1 minute. and within 4 minutes at 205 mPa; at 172 mPa, the virus was not inactivated after 16 minutes of treatment. We have also began to investigate possible mechanisms of virus inactivation by HPP. We found that there was significantly greater variation in virus titers in individual samples of virus treated by HPP than untreated virus. This was not due to aggregation. We prepared clones of SMSV-5 and have tested them to determine if survival correlates with in virus genomic
variations. No variation was detected in genome sequences of cloned viruses prior to (n=30) or after HHP treatment at 205 MPa (n=60), indicating survival is not conferred to a resistant subpopulation of viruses.
Impacts
The emulation of the life cycle of Myxobolus cerebralis in the laboratory can lead to more efficacious and reliable evaluation of the factors that are associated with the establishment and maintenance of the parasite in aquaculture facilities and in wild salmonids. The extended length of the infectious period for the Tubifex worm, the production of prodigous numbers of TAMs, and the ability of a single infected worm or trout to infect the alternate host and cause disease is a fundimental piece of information needed to understand the ability of the parasite to become established in aquaculture facilities and in wild ecosystems. The ability of waders to serve as a mechanical vector of pathogen transmission will directly affect management practices in areas where the pathogen is present. The results of the seafood safety project indicate HHP is a viable method of postharvest processing that can significantly reduce the likelihood of consumers contracting gastroenteritis
from Norwalk-like agents in shellfish.
Publications
- Ogut, H. and Reno, .P.W. 2005. Evaluation of an experimental Aeromonas salmonicida epidemic in chinook salmon, Oncorhynchus tshawytscha (Walbaum). Journal of Fish Diseases 28:263-269.
- Ogut, H. and Reno, P.W. 2005. In vitro host range of aquatic birnaviruses. Bulletin of the European Association of Fish Pathologists 25:53-63.
- Koo, J, Jahncke,ML., Reno,P.W., Hu, X and Mallikarjunan,P. 2005. Inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in Phosphate-Buffered Saline and in Inoculated Whole Oysters by High Pressure Processing. Journal of Food Protection, 68:292-295.
- Ogut, H., LaPatra, S.E., and Reno, P.W. 2005. Effects of host density on furunculosis epidemics determined by the simple SIR model. Preventive veterinary medicine. 71:83-90.
- Park, K.C. and Reno, P.W. 2005. The characteristics of the inhibition of infectious pancreatic necrosis virus (IPNV) by normal rainbow trout (Oncorhynchus mykiss) serum. Diseases of Aquatic Organisms, 63:43-52.
- Ogut, H. and Reno, P.W. 2004. Effects of fish density on spread of infectious hematopoietic necrosis virus (IHNV) in rainbow trout, Oncorhynchus mykiss. Israeli Journal of Aquaculture/Bamidgeh. 56:218-225.
- Childers, R.K., Reno, P.W., and Olson, R.E. 2004. Prevalence, geographic distribution, and biology of a dungeness crab, Cancer magister, microsporidian parasite Journal of Shellfish Research 23:653.
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Progress 01/01/04 to 12/31/04
Outputs
Fish Health: Experiments were conducted to emulate the natural life cycle of Myxobolus cerebralis (Mc) in the laboratory. Carcasses of 3 heavily infected rainbow trout (RBT) were held upstream of 700 Tubifex tubifex (Tt) and allowed to decay naturally in running well water. Worms tested for the production of triactinomyxon spores (TAMs) after 80 d had become infected and produced TAMs at high rates (0.1-11 TAMs/L=144-16000/d). Sentinel RBT placed downstream from the infected Tt were readily infected, even at exposure times as short as 1 minute; RBT exposed for 1 h or more exhibited clinical whirling disease at high levels. When Tt were examined for the prevalence of infection, it was found that more than 70% were infected and producing TAMs. Nearly 2 years after the initial exposure, surviving Tt (approximately 30) were still infected and producing TAMs, but at lower prevalence (6%). We have also determined that a single infected Tt can infect RBT and cause high
levels of clinical whirling disease (75%). The data generated in these experiments is being applied to constructing models for the dissemination of Mc in the rivers of eastern Oregon and other locations in MT, CO, NV, & PA. We are integrating the data obtained from these laboratory experiments with biotic and abiotic data from rivers harboring Mc infection to construct dynamic models of the disease process, especially integrating elements of worm and fish life histories. Seafood Safety Project: The objectives of this work are to determine the optimum HPP operating parameters for inactivating caliciviruses as surrogates of Norwalk agent, and to determine whether the process will be commercially feasible. The virus was capable of surviving >1 month in filtered seawater. Virus uptake by immersion was detected within the oyster within 1 minute, reached saturation within 1 h, where it held for 7 more h, then declined to undetectable levels within 16 h. Uptake was inefficient, with a
maximum of 1% of the total virus load found within the oyster meat and liquor. WIthin the oyster, the majority of the virus was found in liquor and those tissues in contact with the exterior; little virus was found in hemolymph or adductor sinus. This indicates that the likelihood of oyster contamination is temporally limited to the proximity of a contaminating source of virus. High Pressure Processing (HPP) inactivated 107.5 of virus held in cell culture fluid within 2 minutes at 343 mPa (50,000 psi). High pressure processing of oysters immersed in SMSV-5 resulted in a > 5 log reduction in titer at 308 and 274 mPa in less than 1 minute. At a pressure of 205 mPa 4 minutes were required to attain the same level of inactivation. At pressures of 172 mPa, the virus was not inactivated after 16 minutes of treatment. We have also began to investigate possible mechanisms of virus inactivation by HPP. We found that there was significantly greater variation in virus titers in individual
samples of virus treated by HPP than untreated virus. We prepared clones of the virus and will test these clones to determine if the variability correlates with virus genomic sequences.
Impacts
The emulation of the life cycle of Myxobolus cerebralis in the laboratory can lead to more efficacious and reliable evaluation of the factors that are associated with the establishment and maintenance of the parasite in aquaculture facilities and in wild salmonids. Similarly, the experiments with A. salmonicida can help determine methods of abrogating the losses due to furunculosis in aquaculture. The seafood safety product will reduce the likelihood of consumers contracting gastroenteritis from Norwalk-like agents in shellfish.
Publications
- Ogut H., Reno P.W., Sampson, D. 2004. A deterministic model for the dynamics of furunculosis in chinook salmon Oncorhynchus tshawytscha. Diseases of Aquatic Organisms 62:57-63.
- Park KC, Lee S-J, Reno, P.W. 2004. Normal Rainbow Trout Serum (RTS) - resistant variants of Infectious Pancreatic Necrosis Virus (IPNV)-Jasper; differ with respect to inhibition by RTS, Serotype, and cDNA Sequence. Diseases of Aquatic Organisms, 62:45-55.
- Arkoosh, M.R.,Clemons, E., Kagley, A.N., Stafford, C., Jacobson, K. Reno, P.W., Casillas, E., Johnson, L. and Collier,T.K. 2004. Ecological Epidemiology of Salmon Pathogens in Pacific Salmon: Parasites of Salmonid (Onchorhynchus spp.) Populations from Pacific Northwest Estuaries. Journal of Aquatic Animal Health,16:186-196.
- Sollid, S.A., Lorz, H.V., Stevens,D.G., Reno, P.W. and Bartholomew, J.L. 2004. Prevalence of Myxobolus cerebralis at Juvenile Salmonid Acclimation Sites in Northeastern Oregon. North American Journal of Fisheries Management. 24:146-153.
- Ogut, H. and Reno, P.W. 2004. Early Kinetics of Infectious Hematopoietic Necrosis Virus (IHNV) Infection in Rainbow Trout. Journal of Aquatic Animal Health, 16:152-160.
- Ogut, H. and Reno, P.W. 2004. Prevalence of Furunculosis Depends on Density of the Host (Oncorhynchus tshawytscha) Exposed by Cohabitation. North American Journal of Fisheries Management, 24:191-197.
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Progress 01/01/03 to 12/31/03
Outputs
Fish Health: Experiments were conducted to emulate the natural life cycle of Myxobolus cerebralis in the laboratory. The release of myxospores from infected rainbow trout carcasses occurred within 1 week after fish were placed in reservoir water or dechlorinated city water from the same source. Dissolution of the carcasses occurred more readily in the treated water than the reservoir water; similar results were seen with well water vs. dechlorinated tap water. Rainbow trout carcasses heavily infected with the parasite were held upstream of a tank containing Tubifex tubifex and allowed to decay naturally in running well water. Worms tested for the production of triactinomyxon spores (TAMs) after 80 d had become infected from myxospores released by the infected carcasses, and produced TAMs, which continue to be produced at high rates (0.1-11 TAMs/L). Sentinel rainbow trout were placed downstream and physically separated from the infected worms from 24 h (at the
beginning of the experiment) to 1 min. Trout held for 24 h were readily infected and showed signs of clinical whirling disease; similarly, fish held for 1 h exhibited clinical whirling disease. We are currently examining asymptomatic trout exposed for 1 min to infected worms for the presence of myxospores or DNA indicative of infection by PCR. The data generated in these experiments is being applied to constructing models for the dissemination of M. cerebralis in the rivers of eastern Oregon. Retrospective data garnered from the National Wild Fish Health Survey will be amalgamated with the laboratory data for these two diseases and IHN to help assess the risk of infection in wild fishes. Epidemiological experiments with Aeromonas salmonicida in rainbow trout to determine how infection was contracted in early stages of disease supported earlier findings that fish exposed by cohabitation with immersion-infected trout can become infected and die from furunculosis, but that fish that
survive the exposure tend to remain uninfected (48/50 survivors at 21 d).This implies that genotypic or phenotypic factors that preclude infection may be primarily responsible for the severity of disease following exposure, rather than resistance after infection. Seafood Safety Project: The objectives of this phase of the work are to determine the optimum HPP operating parameters for inactivating caliciviruses as surrogates of other SRSVs, and to determine whether the process will be feasible on a commercial scale. The time/dose parameters needed to allow oysters to take up sufficient numbers of caliciviruses (SMSLV) was determined, and it was found that bath immersion for 3 h in seawater containing 105 TCID of virus /ml produced approximately 105 TCID/g of whole oyster meat. This level was maintained for at least 24 h. Within the oyster, the liquor, mantle & viscera contained the highest concentration of virus, with gill and adductor muscle containing significantly less. Individual
oysters assimilated approximately the same amount of virus with relatively small variation among individuals. Preliminary experiments have determined that 276 MPa for 2 m was sufficient to inactivate 99.999% of SMSV in oysters.
Impacts
The emulation of the life cycle of Myxobolus cerebralis in the laboratory can lead to more efficacious and reliable evaluation of the factors that are associated with the establishment and maintenance of the parasite in aquaculture facilities and in wild salmonids. Similarly, the experiments with A. salmonicida can help determine methods of abrogating the losses due to furunculosis in aquaculture. The seafood safety product will reduce the likelihood of consumers contracting gastroenteritis from Norwalk-like agents in shellfish.
Publications
- Pirhonen, J., Schreck, C.B., Reno, P.W., Ogut, H. 2003. Effect of fasting on feed intake, growth and mortality of chinook salmon, Oncorhynchus tshawytscha, during an induced Aeromonas salmonicida epizootic. Aquaculture, 216:31-38.
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