Epidemiology and Control of Infectious Diseases of Salmonids in the Columbia River Basin, 1983 Annual Report.
The Department of Microbiology at Oregon State University with funding from the Bonneville Power Administration conducted a study relating to the epidemiology and control of three fish diseases of salmonids in the Columbia River Basin. These three diseases were ceratomyxosis which is caused by the myxosporidan parasite Ceratomyxa shasta, bacterial kidney disease, the etiological agent of which is Renibacterium salmoninarum, and infectious hematopoietic necrosis, which is caused by a rhabdovirus. Each of these diseases is highly destructive and difficult or impossible to treat with antimicrobial agents. The presence of ceratomyxosis in rainbow trout exposed at McNary and Little Goose Dams extends the range of this disease about 200 miles further up the Columbia River and into the Snake River drainage. Wallowa steelhead trout were less resistant to this disease than other upriver stocks tested. Juvenile salmonids entering the Columbia River estuary were collected periodically between May to September, 1983. Nine percent of the beach seined chinook salmon and 5, 11 and 12%, respectively, of the purse seined coho and chinook salmon and steelhead trout were infected with Ceratomyxa shasta. Experiments indicated ceratomyxosis progresses in salt water at the same rate as in fresh water once the fish have become infected. These data indicate a longer exposure to infective stages of C. shasta than previously identified and that approximately 10% of the migrating salmonids are infected and will probably die from this organism after entering salt water. Since sampling began in 1981 the bacterial kidney disease organism, Renibacterium salmoninarum, has been detected by the fluorescent antibody test in seven salmonid species caught in the open ocean off the coasts of Washington and Oregon. The bacterium has been found primarily in chinook salmon (11%) with lesions in 2.5% of these fish. This disease was also detected at levels ranging from 17% in coho salmon to 25% in chinook salmon seined from the Columbia River just before entering the estuary. Interpretation of these numbers suggests an even greater economic impact on Columbia River salmonid stocks than that proposed for C. shasta. Fertilized eggs from bacterial kidney disease infected parents examined after one month of incubation revealed the presence of bacteria with identical morphology to R. salmoninarum on or in the egg wall further reinforcing the proposed vertical transmission of this disease organism. Infectious hematopoietic necrosis virus was recovered at the 67% level from seeded water samples supplemented with 1% fetal calf serum. Virus injected into unfertilized eggs survived for over two weeks; in eyed eggs the virus also replicated. Epizootics caused by IHNV occurred in two of the 8 separate groups of steelhead trout fingerlings held in LJV treated water at Round Butte Hatchery. Comparing these results to those in the vertical transmission experiment where none of the groups developed IHNV suggests that vertical transmission of IHNV, if it occurs, is a very infrequent or random event. On three occasions IHNV was detected in ovarian fluid samples after storage for 6--9 days at 4 C. No virus had been detected in these samples at spawning. This suggests the presence of an interfering substance, perhaps anti-IHNV antibody in ovarian fluid. This observation raises the possibility that IHNV is much more widespread throughout Columbia River Basin salmonid stocks than previously believed.
- Research Organization:
- Oregon State Univ., Corvallis, OR (United States)
- Sponsoring Organization:
- United States. Bonneville Power Administration.
- DOE Contract Number:
- 1983BP11987
- OSTI ID:
- 758247
- Report Number(s):
- DOE/BP-376; R&D Project: 1983-312-00; TRN: AH200022%%94
- Resource Relation:
- Other Information: PBD: 1 Nov 1984
- Country of Publication:
- United States
- Language:
- English
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Epidemiology and Control of Infectious Diseases of Salmonids in the Columbia River Basin, 1986 Annual Report.
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