Geology topics

A.L. Murray

Publications and source records attributed to A.L. Murray.

7 recordsLinked to original sources

USGS2013

Bench-top validation testing of selected immunological and molecular Renibacterium salmoninarum diagnostic assays by comparison with quantitative bacteriological culture

No gold standard assay exhibiting error-free classification of results has been identified for detection of Renibacterium salmoninarum , the causative agent of salmonid bacterial kidney disease. Validation of diagnostic assays for R. salmoninarum has been hindered by its unique characteristics and biology, and difficulties in locating suitable populations of reference test animals. Infection status of fish in test populations is often unknown, and it is commonly assumed that the assay yielding the most positive results has the highest diagnostic accuracy, without consideration of misclassification of results. In this research, quantification of R. salmoninarum in samples by bacteriological culture provided a standardized measure of viable bacteria to evaluate analytical performance characteristics (sensitivity, specificity and repeatability) of non-culture assays in three matrices (phosphate-buffered saline, ovarian fluid and kidney tissue). Non-culture assays included polyclonal enzyme-linked immunosorbent assay (ELISA), direct smear fluorescent antibody technique (FAT), membrane-filtration FAT, nested polymerase chain reaction (nested PCR) and three real-time quantitative PCR assays. Injection challenge of specific pathogen-free Chinook salmon, Oncorhynchus tshawytscha (Walbaum), with R. salmoninarum was used to estimate diagnostic sensitivity and specificity. Results did not identify a single assay demonstrating the highest analytical and diagnostic performance characteristics, but revealed strengths and weaknesses of each test.

Journal of Fish Diseases↗

USGS2008

Decreased mortality of lake michigan chinook salmon after bacterial kidney disease challenge: Evidence for pathogen-driven selection?

In the late 1960s, Chinook salmon Oncorhynchus tshawytscha from the Green River, Washington, were successfully introduced into Lake Michigan. During spring from1988 to 1992, large fish die-offs affecting Chinook salmon occurred in the lake. Multiple ecological factors probably contributed to the severity of the fish kills, but the only disease agent found regularly was Renibacterium salmoninarum, the causative agent of bacterial kidney disease. in this study, survival after challenge by R. salmoninarum was compared between two Chinook salmon stocks: a Lake Michigan stock from Wisconsin (WI) and the progenitor stock from the Green River. We found that the WI stock had significantly greater survival than the Green River stock. Next, the WI and Green River stocks were exposed to the marine pathogen Listonella anguillarum (formerly Vibrio anguillarum), one of the causative agents of vibriosis; survival after this challenge was significantly poorer for the WI stock than for the Green River stock. A close genetic relationship between the Green River and WI stocks was confirmed by analyzing 13 microsatellite loci. These results collectively suggest that disease susceptibility of Lake Michigan Chinook salmon has diverged from that of the source population, possibly in response to pathogen-driven selection. ?? Copyright by the American Fisheries Society 2008.

Journal of Aquatic Animal Health↗

USGS2006

Both msa genes in Renibacterium salmoninarum are needed for full virulence in bacterial kidney disease

Renibacterium salmoninarum, a gram-positive diplococcobacillus that causes bacterial kidney disease among salmon and trout, has two chromosomal loci encoding the major soluble antigen (msa) gene. Because the MSA protein is widely suspected to be an important virulence factor, we used insertion-duplication mutagenesis to generate disruptions of either the msa1 or msa2 gene. Surprisingly, expression of MSA protein in broth cultures appeared unaffected. However, the virulence of either mutant in juvenile Chinook salmon (Oncorhynchus tshawytscha) by intraperitoneal challenge was severely attenuated, suggesting that disruption of the msa1 or msa2 gene affected in vivo expression. Copyright ?? 2006, American Society for Microbiology. All Rights Reserved.

Applied and Environmental Microbiology↗

USGS2005

A cohabitation challenge to compare the efficacies of vaccines for bacterial kidney disease (BKD) in chinook salmon Oncorhynchus tshawytscha

The relative efficacies of 1 commercial and 5 experimental vaccines for bacterial kidney disease (BKD) were compared through a cohabitation waterborne challenge. Groups of juvenile chinook salmon Oncorhynchus tshawytscha were vaccinated with one of the following: (1) killed Renibacterium salmoninarum ATCC 33209 (Rs 33209) cells; (2) killed Rs 33209 cells which had been heated to 37??C for 48 h, a process that destroys the p57 protein; (3) killed R. salmoninarum MT239 (Rs MT239) cells; (4) heated Rs MT239 cells; (5) a recombinant version of the p57 protein (r-p57) emulsified in Freund's incomplete adjuvant (FIA); (6) the commercial BKD vaccine Renogen; (7) phosphate-buffered saline (PBS) emulsified with an equal volume of FIA; or (8) PBS alone. Following injection, each fish was marked with a subcutaneous fluorescent latex tag denoting its treatment group and the vaccinated fish were combined into sham and disease challenge tanks. Two weeks after these fish were vaccinated, separate groups of fish were injected with either PBS or live R. salmoninarum GL64 and were placed inside coated-wire mesh cylinders (liveboxes) in the sham and disease challenge tanks, respectively. Mortalities in both tanks were recorded for 285 d. Any mortalities among the livebox fish were replaced with an appropriate cohort (infected with R. salmoninarum or healthy) fish. None of the bacterins evaluated in this study induced protective immunity against the R. salmoninarum shed from the infected livebox fish. The percentage survival within the test groups in the R. salmoninarum challenge tank ranged from 59% (heated Rs MT239 bacterin) to 81 % (PBS emulsified with FIA). There were no differences in the percentage survival among the PBS-, PBS/FIA-, r-p57-and Renogen-injected groups. There also were no differences in survival among the bacterin groups, regardless of whether the bacterial cells had been heated or left untreated prior to injection. ?? Inter-Research 2005.

Diseases of Aquatic Organisms↗

USGS2003

Effects of ration level on immune functions in chinook salmon (Oncorhynchus tshawytscha)

The relationship between nutritional status and disease resistance in cultured salmonids can be affected by dietary manipulations. Careful attention to feeding levels may be important to avoid imbalances in nutrient levels that could ultimately impair a fish's ability to resist infectious microorganisms. In the current study, fish in three feed-level groups were fed an experimental diet either to satiation, 64% of satiation or 40% of satiation. A fourth group of fish were fed a commercial diet at the 64% of satiation level and served as controls. To evaluate certain indices of disease resistance in the test and control fish, a panel of assays was employed to measure humoral and cellular immune functions 30, 39 and 54 weeks after starting the dietary treatments. The panel included measures of blood hematocrit and leucocrit levels, plasma protein concentration and serum lysozyme and complement activity. Cellular analyses included differential blood leucocyte counts, NBT reduction and phagocytosis by pronephros macrophages and myeloperoxidase activity of pronephros neutrophils. No differences were observed in those indices between fish tested from the control-diet group (commercial diet fed at the 64% rate) and fish tested from the 64% feed-level group, except that fish fed the commercial diet had a greater concentration of plasma protein. Leucocrit values and plasma protein concentrations tended to increase among the experimental feed groups as the ration increased from 40% to satiation. More importantly, phagocytic activity by anterior kidney leucocytes was found to be inversely proportional to the feed level. Whereas the results of this study provide evidence that the salmonid immune system may be fairly robust with regard to available metabolic energy, the significant changes observed in phagocytic cell activity suggest that some cellular immune functions may be affected by the feed level.

Aquaculture↗

USGS2003

Effects of various feed supplements containing fish protein hydrolysate or fish processing by-products on the innate immune functions of juvenile coho salmon (Oncorhynchus kisutch)

Immunomodulators administered to fish in the diet have been shown in some cases to enhance innate immune defense mechanisms. Recent studies have suggested that polypeptide fractions found in fish protein hydrolysates may stimulate factors in fish important for disease resistance. For the current study, groups of coho salmon were reared on practical feeds that contained either fish meal (Control diet), fish meal supplemented with cooked fish by-products, or fish meal supplemented with hydrolyzed fish protein alone, or with hydrolyzed fish protein and processed fish bones. For each diet group, three replicate tanks of fish were fed the experimental diets for 6 weeks. Morphometric measurements, and serologic and cellular assays were used to evaluate the general health and immunocompetence of fish in the various feed groups. Whereas the experimental diets had no effect on the morphometric and cellular measurements, fish fed cooked by-products had increased leucocrit levels and lower hematocrit levels than fish from the other feed groups. Innate cellular responses were increased in all feed groups after feeding the four experimental diets compared with pre-feed results. Subgroups of fish from each diet group were also challenged with Vibrio anguillarum (ca. 7.71 ?? 105 bacteria ml-1) at 15??C by immersion. No differences were found in survival among the various feed groups.

Aquaculture↗

USGS2002

Effects of rearing temperature on immune functions in sockeye salmon (Oncorhynchus nerka)

To determine if the defences of sockeye salmon (Oncorhynchus nerka) raised in captivity are affected by the rearing temperature or their life-cycle stage, various indices of the humoral and cellular immune functions were measured in fish reared at either 8 or 12??C for their entire life-cycle. Measures of humoral immunity included the commonly used haematological parameters, as well as measurements of complement, and lysozyme activity. Cellular assays quantified the ability of macrophages from the anterior kidney to phagocytise Staphylococcus aureus cells, or the activities of certain bactericidal systems of those cells. The T-dependent antibody response to a recombinant 57 kDa protein of Renibacterium salmoninarum was used to quantify the specific immune response. Fish were sampled during the spring and fall of their second, third and fourth years, corresponding to a period that began just before smolting and ended at sexual maturation. Fish reared at 8??C tended to have a greater percentage of phagocytic kidney macrophages during the first 2 years of sampling than the fish reared at 12??C. During the last half of the study the complement activity of the fish reared at 8??C was greater than that of the 12??C fish. Conversely, a greater proportion of the blood leucocytes were lymphocytes in fish reared at 12??C compared to the fish reared at 8??C. Fish reared at 12??C also produced a greater antibody response than those reared at 8??C. Results suggested that the immune apparatus of sockeye salmon reared at 8??C relied more heavily on the non-specific immune response, while the specific immune response was used to a greater extent when the fish were reared at 12??C. Although a seasonal effect was not detected in any of the indices measured, varying effects were observed in some measurements during sexual maturation of fish in both temperature groups. At that time there were dramatic decreases in complement activity and lymphocyte numbers. This study was unique in its scope because it was the first quantitative assessment of salmon immune functions for an entire life-cycle. ?? 2002 Elsevier Science Ltd.

Fish and Shellfish Immunology↗