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G. L. Bullock

Publications and source records attributed to G. L. Bullock.

At least 19 recordsLinked to original sources
USGS2006

Enteric redmouth bacterium: Comparison of isolates from different geographic areas

Characteristics of 18 strains of Yersinia ruckeri the causative agent of enteric redmouth disease, from a variety of hosts and a wide geographic range were compared. Except for variations in colonial morphology and in citrate, sorbitol, and trehalose reactions, the strains were morphologically and biochemically homogeneous. Sixteen strains reacted with antiserum against the first serotype reported, and one strain reacted with antiserum against a more recently reported serotype. One strain represented a third serotype. Evidence presented indicated that extension of the geographic range may not be entirely a result of the transport of carrier fish.

Journal of Fish Diseases↗
USGS2006

An acute septicaemic disease of brown trout (Salmo trutta) and Atlantic salmon (Salmo salar) caused by a Pasteurella-like organism

Ulcerations of the skin associated with haemorrhagic petechiae of liver and kidneys, were the main signs of disease affecting salmon and brown trout in Norway. A death rate of 15–20% was estimated for the 5 month period of mid-March-August, although mortalities occurred throughout the year. Bacteriological examinations, involving 36 isolates, suggested the causual organism to be a Pasteurella although the DNA homology examination gave a G.C. ratio of 55.6 % which is high for Pasteurella as a group.

Journal of Fish Biology↗
USGS2001

Evaluation of commercially prepared transport systems for nonlethal detection of Aeromonas salmonicida in salmonid fish

In vitro studies indicated that commercially prepared transport systems containing Amies, Stuart's, and Cary-Blair media worked equally well in sustaining the viability of the fish pathogen Aeromonas salmonicida, which causes furunculosis. The bacterium remained viable without significant increase or decrease in cell numbers for as long as 48 h of incubation at 18-20??C in Stuart's transport medium; consequently, obtaining mucus samples in such tubes were comparable to on-site detection of A. salmonicida by dilution plate counts on Coomassie Brilliant Blue agar. In three different assays of 100 samples of mucus from Atlantic salmon Salmo salar infected subclinically with A. salmonicida, dilution counts conducted on-site proved more reliable for detecting the pathogen than obtaining the samples in the transport system. In the on-site assays, dilution counts detected the pathogen in 34, 41, and 22 samples, whereas this was accomplished in only 15, 15, and 3 of the respective samples when the transport system was used. In an additional experiment, Arctic char Salvelinus alpinus sustaining a frank epizootic of furunculosis were sampled similarly. Here, too, dilution counts were more predictive of the prevalence of A. salmonicida and detected the pathogen in 46 mucus samples; in comparison, only 6 samples collected by using the transport system were positive. We also observed that the transport system supported the growth of the normal mucus bacterial flora. Particularly predominant among these were motile aeromonads and Pseudomonas fluorescens. In studies of mixed culture growth, two representatives of both of the latter genera of bacteria outgrew A. salmonicida - in some cases, to the total exclusion of the pathogen itself.

Journal of Aquatic Animal Health↗
USGS1997

Recurrent amoebic gill infestation in rainbow trout cultured in a semiclosed water recirculation system

Five lots of commercially purchased juvenile rainbow trout Oncorhynchus mykiss (17–44 g) stocked in a continuous-production water recirculation system became infested with gill amoebae. The amoebae were introduced into the recirculation system, as evidenced by their presence on gills of fish held in quarantine tanks. Based on their morphology, as seen in histological sections and by electron microscopy, the amoebae appeared to be more closely related to the family Cochliopodiidae than to other taxa of free-living amoebae. Attempts to culture the amoebae in different media, at different temperatures of incubation, and in fish cell culture were not successful. Initial treatment of the recirculation system with formalin at 167 parts per million (ppm) for 1 h eliminated amoebae from the gills. Subsequent treatments of the entire system with formalin at 50–167 ppm reduced the intensity of further infestations.

Journal of Aquatic Animal Health↗
USGS1996

Nature of Aeromonas salmonicida carriage on asymptomatic rainbow trout maintained in a culture system with recirculating water and fluidized sand biofilters

An asymptomatic carrier population of rainbow trout Oncorhynchus mykiss was examined for Aeromonas salmonicida by primary dilution counts on Coomassie Brilliant Blue agar and also by streaking on bacteriological media after a 24–48-h pre-enrichment in tryptic soy broth. The pathogen was detected by primary dilution plate counts in 1 spleen, 15 gill, and 19 mucus samples of the 100 trout examined. Aerornonas samonicida was detected only after 48-h preenrichment in the one spleen that had already tested positive via primary dilution counts. The pathogen was not detected in kidney, liver, and intestinal samples. The occurrence of the pathogen in mucus and gills suggests a predominantly external nature of asymptomatic carriage of A. salmonicida within this population of fish. Repeated examination of fluidized biofilters and tank water showed that A. salmonicida did not become established in the recirculation system.

Journal of Aquatic Animal Health↗
USGS1994

Observations on the occurrence of bacterial gill disease and amoeba gill infestation in rainbow trout cultured in a water recirculation system

Spontaneous outbreaks of bacterial gill disease (BGD) occurred in 17-44-g rainbow trout Oncorhynchus mykiss after they were placed in a water recirculation system. In each of five groups stocked from September 1991 through July 1992, BGD occurred within 6–8 d after stocking. In each instance, BGD was followed by a secondary amoeba infestation. The spontaneous BGD outbreaks did not occur among previously stocked groups that had recovered from earlier BGD disease outbreaks. Examination of gill tissue by Gram stain and indirect fluorescent antibody technique showed increased numbers of filamentous bacteria associated with BGD after the rainbow trout were stocked into the system. Bacterial numbers decreased after a 1-h treatment with chloramine-T at concentrations of 9–15 mg/L but increased within 2 d after treatment. Although the chloramine-T treatments controlled mortality related to BGD, the amoeba infestation persisted. Histological examination of gills showed some focal hyperplasia before the rainbow trout were placed into the recirculation system, but hyperplasia became more extensive and lamellar fusion and mild telangiectasis developed within a week after placement in the system. The density at which the fingerling rainbow trout were stocked and the suspended solids present in tank water may have contributed to the BGD outbreaks. Exposure of juvenile rainbow trout to tank water from the recirculation system before they were placed into the system did not afford them protection against BGD after stocking.

Journal of Aquatic Animal Health↗
USGS1991

Hatchery efficacy trials with chloramine-T for control of bacterial kidney disease

Three hatchery trials were carried out to determine the efficacy of chloramine-T for the control of bacterial gill disease in rainbow trout Oncorhynchus mykiss , ranging in weight from 2.5 to 54 g. In each trial, we used a single flow-through treatment of 8.5 mg chloramine-T/L. The single treatment provided effective control in all three trials; however, results were best when treatment was begun in the early stages of an outbreak. A second or third treatment may be required if an outbreak is in an advanced stage or if fish are under stress.

Journal of Aquatic Animal Health↗
USGS1989

Developments in the control of bacterial kidney disease of salmonid fishes

Bacterial kidney disease of salmonid fishes, caused by Renibactenum salrnoninarum, was first reported more than 50 yr ago; nevertheless, large gaps persist in our knowledge of the infection - particularly in methods for its control. In the 1950's, principal control measures consisted of prophylactic or therapeutic feeding of sulfonamides, which were later supplanted by the antibiotic erythromycin. Chemotherapy has effected some reduction of mortality, but benefits are typically transient and mortality usually resumes after the drug is withdrawn. Some studies have indicated that diet composition affects the prevalence and severity of the disease. Although tests of chemotherapeutants and diet modification have continued, research emphasis has shifted partly toward prevention of the disease by breaking the infection cycle. It is now generally accepted that R. salrnoninarum can be transmitted both vertically and horizontally. Experimental evidence indicates that immersion of newly fertilized eggs in iodophor or erythromycin does not prevent vertical transmission. However, the injection of female salmon with erythromycin before they spawn shows promise as a practical means of interrupting vertical transmission. The results of attempts to prevent infection of juvenile salmonids by vaccination against bacterial kidney disease have been disappointing, thus underscoring a basic need for a better understanding of protective mechanisms in salmonids. The recent development of more sensitive and quantitative detection methods should aid in evaluating the efficacy of current and future control strategies.

Diseases of Aquatic Organisms↗