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Geology topics

L.A. Ford

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

At least 19 recordsLinked to original sources
USGS1998

Control of furunculosis and enteric redmouth disease in sea-run Atlantic salmon broodstock in the Connecticut and Merrimack Rivers

Adult sea‐run Atlantic salmon Salmo salar captured and transported to Richard Cronin National Salmon Station (Sunderland, Massachusetts), Nashua National Fish Hatchery (Nashua, New Hampshire), and Whittemore State Fish Hatchery (Waterford, Connecticut) during 1986–1992 were treated with oxolinic acid and a bacterin. The bacterin was developed against furunculosis and enteric redmouth disease. Among the 2,552 fish that were treated since 1986, 362 died and 65 (18%) of those fish had furunculosis. Among 206 untreated fish that were maintained as controls, 109 died and 63 (57.8%) had furunculosis. The reduction in mortality could not be attributed to either vaccine or antibiotic alone without further study. A 3‐year study was designed to investigate if adult Atlantic salmon, undergoing the stress of migration, handling, and spawning, could mount a protective humoral immune response. Although the salmon were able to produce an agglutinin response, evidence was not found for production of a protective humoral response by these vaccinated Atlantic salmon.

Progressive Fish-Culturist↗
USGS1996

Monitoring for early detection of Aeromonas salmonicida to enhance antibiotic therapy and control furunculosis in Atlantic salmon

Juvenile Atlantic salmon Salmo salar at the White River National Fish Hatchery were monitored quarterly for Aeromonas salmonicida , the etiologic agent of furunculosis. Samples were obtained in August, November, January, and March, within an 8‐month smolt production cycle during 1992–1993. Aeromonas salmonicida was isolated in August from external mucus and kidneys of fish within six production pools, each containing about 7,500 fish. Topical disinfection with a 60‐min bath of Chloramine‐T at 15 mg/L on three consecutive days did not control the prevalence of infection. Atlantic salmon were then fed 77.0 mg of oxytetracycline per kilogram of fish for 10 d. Mortality subsided in all tanks within 4 d after initiation of oral antibiotic therapy. Further examination failed to isolate the pathogen 21 d after cessation of treatment. In November, A. salmonicida was detected in the mucus of one fish from a single tank; treatment was not prescribed. Pathogens were not detected shortly after fish were marked with coded wire tags in January or prior to release in March. Monitoring programs allowed early detection of the pathogen; this led to treatment that permitted fish to be stocked in accordance with established fish health policy regulations for salmonids in New England.

Progressive Fish-Culturist↗
USGS1996

Epizootiological study of bacterial cold-water disease in Pacific salmon and further characterization of the etiologic agent, Flexibacterin psychrophila

Isolates of Flexibacter psychrophila were obtained from chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch that had previously sustained epizootics of coldwater disease. The pathogen was readily isolated from kidney and mucus of convalescent fish. The organisms were relatively inert in most standard microbiological media but were structurally and serologically homogenous by examination of whole cell protein lysates by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In contrast to the homogeneity observed in phenotypic and serologic assays, the isolates studied elaborated varied ribotypes. All isolates produced a single rDNA spacer amplification product of about 240 base pairs.

Journal of Aquatic Animal Health↗
USGS1996

Control of external Aeromonas salmonicida: topical disinfection of salmonids with Chloramine-T

Brook trout Salvelinus fontinalis were treated with single 60-min static baths of 250 mg formalin/L, 3% NaCl, and 15 mg Chloramine-T/L to evaluate the efficacy of these compounds against external infections of Aeromonas salmonicida. Prevalence of A. salmonicida was significantly lower in brook trout treated with Chloramine-T than among those treated with formalin or salt. Further laboratory tests substantiated the therapeutic value of a single treatment of ChloramineT (15 mg/L) against A. salmonicida . In two experiments, viable counts of A. salmonicida in mucus did not vary among replicate groups of treated brook trout, but the counts for treated fish were significantly (P < 0.05) lower than those for untreated controls. In vitro tube dilution assays indicated that mean minimum inhibitory concentrations of Chloramine-T for 10 isolates of A. salmonicida were 9.0 mg/L for 1 h and 2.25 mg/L, for 24 h. In field trials at the White River National Fish Hatchery (Bethel, Vermont), the pathogen was detected principally as an external infection of juvenile Atlantic salmon Salmo solar maintained in two culture ponds. In one pond, the bacterium accounted for 100% of the total distribution of tnicroflora isolated from mucus. Seven days after treatment with Chloramine-T, A. sahnonicida accounted for 11% of the total bacterial counts identified from these fish. In the second pond, A. salmonicida composed 3% of the counts of bacteria isolated from the mucus of fish before treatment but was not isolated after treatment.

Journal of Aquatic Animal Health↗
USGS1996

Use of non-lethal procedures to detect and monitor Aeromonas salmonicida in potentially endangered or threatened populations of migrating and post-Spawning salmon

Non-lethal assay of mucus was assessed for detection of Aeromonas salmonicida among feral populations of salmon returning to the Salmon River (Altmar, NY, USA). A. salmonicida was isolated from returns of 2 year classes of coho Oncorhynchus kisutch and chinook O. tshawytscha salmon. Data suggested that non-lethal assay of mucus was comparable to standard lethal procedures used to detect and isolate A. salmonicida from kidney tissues. Non-lethal procedures were also used to detect A. salmonicida and monitor the effectiveness of antibiotic therapy for the control of furunculosis among valuable Atlantic salmon Salmo salar broodstock maintained at the Richard Cronin National Salmon Station (Sunderland, MA, USA).

Diseases of Aquatic Organisms↗
USGS1994

Isolation of Aeromonas salmonicida from paddlefish, Polyodon spathula

Aeromonas salmonicida was isolated from paddlefish ( Polyodon spathula ) mortalities collected during an epizootic of furunculosis at the Spring River State Hatchery, Arkansas (USA), in 1992. Isolates of the bacterium were obtained from culture of gill and kidney tissue. This is the first epizootic of bacterial etiology to be reported in paddlefish.

Arkansas↗
USGS1994

Relationship between resistance of salmonids to furunculosis and recovery of Aeromonas salmonicida from external mucus

Fish were sampled at the Ed Weed State Fish Hatchery (South Hero, Vermont, USA) in September 1992. Aeromonas salmonicida was common, with concentrations as high as 10 5 to 10 7 colony-forming units per gram of mucus, and readily recovered from most mucus samples obtained from furunculosis-sensitive populations of brook trout ( Salvelinus fontinalis ), lake trout ( Salvelinus namaycush ), and Atlantic salmon (Salmo salar) . The pathogen was the predominant microorganism and accounted for greater than 85% of the total number of bacteria isolated from the mucus of these fish. By comparison, A. salmonicida was recovered only from two rainbow trout ( Oncorhynchus mykiss ), and bacterial frequencies did not exceed 10 3 colony-forming units per gram of mucus. The pathogen was not recovered from the mucus of steelhead ( O. mykiss ) or Rome brown trout ( Salmo trutta ) selectively bred for resistance to furunculosis, even though there was widespread contagion throughout the hatchery and fish were cultured on a common, unprotected water supply.

Journal of Wildlife Diseases↗
USGS1992

Detection of Aeromonas salmonicida the mucus of salmonid fishes

Mucus of salmonids was evaluated as a source for nonlethal detection of the pathogen Aeromonas salmonicida in fish. The bacterium was readily isolated from mucus on dilution plates when Coomassie Brilliant Blue agar was the primary plating medium. Kidney samples from the fish that served as sources of mucus were similarly processed. Infection was detected in 56% of mucus samples from lake trout Salvelinus namaycush that were undergoing an epizootic of furunculosis, but only 6% of the kidneys from these fish were positive for the pathogen. Only 1% of asymptomatic brown trout Salmo trutta sampled at another fish hatchery had A. salmonicida in their mucus, and none had a kidney infection. Combined results from the examination of two pools of Atlantic salmon Salmo salar reared at a third hatchery indicated that 37% of these fish had mucus infections caused by A. salmonicida , but only 4% of the kidneys were infected.

Journal of Aquatic Animal Health↗