Geology topics

Ronald J. Pascho

Publications and source records attributed to Ronald J. Pascho.

6 recordsLinked to original sources

USGS2006

Detection of infectious haematopoietic necrosis virus in river water and demonstration of waterborne transmission

In a study of the possible role of waterborne infectious haematopoietic necrosis virus in transmission of the disease among spawning sockeye salmon, Oncorhynchus nerka (Walbaum), both infection rates and virus titres were higher in fish held at high density in a side channel than in fish in the adjacent river. Virus was never isolated from river water, but was found in water from the side channel at levels ranging from 32.5 to 1600 plaque-forming units (p.f.u.)/ml. Uninfected yearling sockeye salmon held in a box in the side channel developed localized gill infections with IHN virus. The disease did not progress to the viscera until a threshold titre of about 10 5 p.f.u./g was reached in the gill. The effectiveness of the gill as a barrier limiting development of systemic infections means that waterborne IHN virus probably does not greatly increase the infection rate in a sockeye salmon population during spawning.

Journal of Fish Diseases↗

USGS1998

Comparison of the membrane-filtration fluorescent antibody test, the enzyme-linked immunosorbent assay, and the polymerase chain reaction to detect Renibacterium salmoninarum in salmon ovarian fluid

Ovarian fluid samples from naturally infected chinook salmon ( Oncorhynchus tshawytscha ) were examined for the presence of Renibacterium salmoninarum by the membrane-filtration fluorescent antibody test (MF-FAT), an antigen capture enzyme-linked immunosorbent assay (ELISA), and a nested polymerase chain reaction (PCR). On the basis of the MF-FAT, 64% (66/103) samples contained detectable levels of R. salmoninarum cells. Among the positive fish, the R. salmoninarum concentrations ranged from 25 cells/ml to 4.3 × 10 9 cells/ml. A soluble antigenic fraction of R. salmoninarum was detected in 39% of the fish (40/103) by the ELISA. The ELISA is considered one of the most sensitive detection methods for bacterial kidney disease in tissues, yet it did not detect R. salmoninarum antigen consistently at bacterial cell concentrations below about 1.3 × 10 4 cells/ml according to the MF-FAT counts. When total DNA was extracted and tested in a nested PCR designed to amplify a 320-base-pair region of the gene encoding a soluble 57-kD protein of R. salmoninarum , 100% of the 100 samples tested were positive. The results provided strong evidence that R. salmoninarum may be present in ovarian fluids thought to be free of the bacterium on the basis of standard diagnostic methods.

Journal of Veterinary Diagnostic Investigation↗

USGS1995

Brood stock segregation for the control of bacterial kidney disease can affect mortality of progeny chinook salmon (Oncorhynchus tshawytscha) in seawater

Segregation of spring chinook salmon ( Oncorhynchus tshawytscha ) brood stock based on the measurement of maternal Renibacterium salmoninarum infection levels by the enzyme-linked immunosorbent assay (ELISA) and the fluorescent antibody technique (FAT) was previously shown to affect the prevalence and levels of bacterial kidney disease (BKD) in progeny fish during hatchery rearing. Smolts from that study were subjected to standardized fish health and condition evaluation procedures 2 weeks before the conclusion of hatchery rearing and release of the fish for migration to the Pacific Ocean. The results suggested that the general health of the smolts in the progeny group from parents that had low R. salmoninarum infection levels or tested negative for R. salmoninarum (low-BKD group) was better than that of the smolts in the progeny group from female parents with high R. salmoninarum infection levels (high-BKD group). Testing by the ELISA showed that the overall severity of R. salmoninarum infection also was lower in the smolts from the low-BKD group. Subgroups of smolts from the study were acclimated to tanks of seawater for extended holding. After a 22-day acclimation period and 98 days in full-strength (29 ppt salinity) seawater, total mortality was 12% in the low-BKD group and 44% in the high-BKD group. All of the mortality in the low-BKD group and 85% of the mortality in the high-BKD group occurred after the fish were transferred to full-strength seawater. Testing of kidney tissues from all dead fish by the FAT revealed that 85% of the fish that died in the high-BKD group had high R. salmoninarum numbers, indicating that BKD was the cause of death. In contrast, none of the fish that died in the low-BKD group had detectable numbers of R. salmoninarum . We concluded that brood stock segregation by use of the ELISA and the FAT can affect mortality and the R. salmoninarum status of progeny chinook salmon for as long as 21 months after hatching, even after the fish have been transferred to seawater.

Aquaculture↗

USGS1994

Effect of dietary vitamin E and selenium on growth, survival and the prevalence of Renibacterium salmoninarum infection in chinook salmon (Oncorhynchus tshawytscha)

Groups of juvenile spring chinook salmon naturally infected with Renibacterium salmoninarum , the causative agent of bacterial kidney disease, were fed diets containing different levels of vitamin E and selenium for 214 days in fresh water and 110 days in seawater. The fish were fed vitamin E at concentrations of either 53±3 mg (designated e ) or 299±9 mg (designated E ) α -tocopheryl acetate equivalence/kg dry diet in combination with sodium selenite to give selenium concentrations of either 0.038±0.008 mg (designated s ) or 2.49±0.15 mg (designated S )/kg dry diet. No mortality occurred in the group fed the diet, whereas mortality was 3% in the groups fed the and diets, and 31% in the group fed the diet. At the end of the experiment, weight gain and hematocrit values were significantly greater in those fish fed the E diets compared with those fed the e diets, whereas the hepato-somatic index was significantly higher in fish fed the e diets. Glutathione peroxidase activity in blood plasma was significantly higher in fish fed the S diets compared with those fed the s diets. No definite effect of dietary vitamin E and selenium on the prevalence and severity of natural R. salmoninarum infections was demonstrated.

Aquaculture↗

USGS1993

Monitoring of the in-river migration of smolts from two groups of spring chinook salmon, Oncorhynchus tshawytscha (Walbaum), with different profiles of Renibacterium salmoninarum infection

Broodstock segregation based on the measurement of maternal Renibacterium salmoninarum infection levels by the enzyme-linked immunosorbent assay (ELISA) and the membrane filtration-fluorescent antibody technique (MF-FAT) was previously shown to affect the prevalence and levels of bacterial kidney disease (BKD) in progeny of chinook salmon, Oncorhynchus tshawytscha (Walbaum), during hatchery rearing. Subgroups of fish from that study were marked with passive integrated transponder (PIT) tags, and monitored by PIT-tag detectors during the first 342km of their migration to the Pacific Ocean. Differences in the recovery of tagged fish were significant ( P ≤ 0·01) at each detection point and became more pronounced as the fish moved downstream. Cumulative recoveries of fish from the low-BKD group and the high-BKD group, respectively, were 31% and 28% after 116km, 44% and 37% after 176km, and 51% and 42% after 342km. There were no apparent differences in the migration timing of the two groups to the first detection point. The data suggested that in-river survival was higher in the progeny group from parents that had low R. salmoninarum infection levels or tested negative for R. salmoninarum (low-BKD group) than in the group female parents with high infection levels (high-BKD group).

Aquaculture Research↗

USGS1991

Brood stock segregation of spring chinook salmon Oncorhynchus tshawytscha by use of the enzyme-linked immunosorbent assay (ELISA) and the fluorescent antibody technique (FAT) affects the prevalence and levels of Renibacterium salmoninarum infection in progeny

A study of the effect of maternal Renibacterium salmoninarum infection levels on the prevalence and levels of bacterial kidney disease (BKD) in progeny fish was conducted at a production salmon hatchery. A total of 302 mating pairs of spring chinook salmon Oncorhynchus tshawytscha was screened in August 1988 for R. salmoninarum by an enzyme-linked immunosorbent assay (ELISA). On the basis of ELISA testing of kidney tissues from all fish and the testing of ovarian fluid samples from a subsample of the females by a direct membrane filtration fluorescent antibody technique (MF-FAT), selected egg lots were segregated into 2 groups of 30 egg lots or about 135 000 eggs each. One group contained egg lots from male and female parents that had low R. salmoninarum infection levels or tested negative for R. salmoninarum (low-BKD group), and the other group contained egg lots from female parents with relatively high R. salmoninarum infection levels and male parents with various infection levels (high-BKD group). The progeny groups were maintained in separate rearing units supplied with untreated river water, and were monitored for R. salmoninarum by the ELISA until they were released from the hatchery in April 1990. Total mortality of the juvenile fish was higher (p = 0.0001) in the high-BKD group (20%) than in the low-BKD group (10 %). Mortality in the high-BKD group was highest after the fish were moved from nursery tanks to raceways, and clinical BKD became evident in this group. During the 11 mo of raceway rearing, mortality in the high-BKD group was 17 % compared with 5 % for the low-BKD group. An ELISA analysis of smolts just before release showed an R. salmoninarum infection rate of 85 % in the high-BKD group and 62 % in the low-BKD group. Of the positive fish, 98 % in the low-BKD group and 55 % in the high-BKD group had low infection levels, whereas 36 % in the high-BKD group and only 1 % in the low-BKD group had high infection levels. The results of this research suggest that segregation of brood stock by the ELISA and the MF-FAT can be used to reduce the prevalence and levels of BKD in hatchery-reared spring chinook salmon, even in locations with open water supplies.

Diseases of Aquatic Organisms↗