• Journal of fish pathology
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• v.23 no.2
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• pp.155-163
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• 2010

The epidemiological study was performed to survey the prevalence of fish pathogens in cultured olive flounder, Paralichthys olivaceus from 2005 to 2007. In this study, the fish pathogens were detected from 1,528 among 2,238 fish samples collected yearly in 5 sites from February, May, August and November. Annual incidences for three years show a yearly increase and there were 60.6% in 2005, 66.7% in 2006 and 72.3% in 2007, respectively. Seasonal prevalence was 63.5% in February, 67.4% in May, 75.1% in August and 64.4% in November for three years. The detection rates of 6 viral pathogens were 35.6% in 2005, 44.6% in 2006 and 24.4% in 2007 and the peak rate was 55.4% at adult size group (above 41cm). Viral nervous necrosis virus (24.7%) has been the most predominant virus in this investigation, while much lower rates were noted in viral haemorrhagic septicemia virus (10.6%) and red sea bream iridovirus (0.9%).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.1
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• pp.18-22
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• 2014

The antibacterial activities of methanol extracts of 19 commercial herbal medicines were measured against the fish pathogens Vibrio ichthyoenteri and Streptococcus iniae, which cause several fish diseases. Rhus javanica showed the strongest antibacterial activity against V. ichthyoenteri and S. iniae. The methanol extract of R. javanica was extracted further using several organic solvents with different polarities. The extract from the ethyl acetate fraction showed strong activity against both fish pathogens. The minimum inhibitory concentration (MIC) of the R. javanica extract was $32{\mu}g/mL$ for V. ichthyoenteri and $128{\mu}g/mL$ for S. iniae. Further purification and isolation of the active compound (s) responsible for these activities and further study of the synergistic effect using combinations of antibiotics against pathogenic bacteria are needed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.3
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• pp.443-450
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• 2020

No established method can be used to select effective antibiotics in antibiotic susceptibility tests for fish bacterial pathogens quickly and accurately. Here, we established the optimal conditions for determining the minimal inhibitory concentration (MIC) of major fish bacterial pathogens (Streptococcus spp., Edwardsiella tarda, Vibrio spp., Aeromonas spp., and Pseudomonas spp.) using the KRAQ1 and CAMPY2 panels. The MIC panel used 18 antibiotics of two types and we conducted experiments to establish the optimal culture medium and temperature for each species. The optimal conditions for incubating Streptococcus spp. were in cation-adjusted Mueller-Hinton broth with TES buffer (CAMHBT) at 28℃, using 5% lysed horse blood (LHB) as recommended by the Clinical Laboratory Standards Institute. For Vibrio spp., the optimal culture conditions were 28℃ in CAMHBT supplemented with 1% NaCl. The optimal conditions for culturing E. tarda, Aeromonas spp., and Pseudomonas spp. were in CAMHBT at 28℃.

• Microbiology and Biotechnology Letters
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• v.44 no.4
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• pp.535-539
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• 2016

The prevalence of pathogenic bacteria such as Streptococcus parauberis (Sp), Streptococcus iniae (Si), and Edwardsiella tarda (Et) in flounder fish farms in Jeju Island and their management by gallium treatment was studied. Sp, Si, and Et were found to exhibit a low rate of cell growth and high biofilm formation. Hence, in the present study, cell growth and biofilm formation were measured spectrophotometrically 72 h after the addition of different concentrations of gallium (2, 4, or 8 mg/ml). In addition, cell death was measured by resazurin and propidium iodide staining assays. The results showed that bacterial cell death increased and biofilm formation decreased with an increasing concentration of gallium. Hence, the present study signifies that the use of gallium against bacterial pathogens could be useful for disease management in flounder farms.

• Journal of fish pathology
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• v.34 no.2
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• pp.255-259
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• 2021

This is the first report describing acute mass mortality occurred in juvenile olive flounder (Paralichthys olivaceus) caused by gas bubble disease (GBD). A total of 610 fish (average weight = 35 g), which were more than half of the fish acclimated at 17℃ in an aquarium, were killed within two days of acclimation. The dead and moribund fish showed excessively opened opercula and mouths, and occasionally, severe exophthalmia. Through microscopic observation, numerous gas emboli were found in the gills of the dead and live fish, while the fish were not infected with any microbial pathogens. The dissolved oxygen (DO) saturation level of the rearing water and seawater nearby the facility reached 145% and 286%, respectively, whereas other water quality parameters (such as salinity, pH, and chemical oxygen demand) were normal. The extreme saturation rate of seawater in the shore nearby seemed to be due to an enormous algal bloom that occurred there. Through molecular identification based on 18S rDNA sequences, the most dominant algal species was most closely related to Ulva californica (99.87% sequence identity) followed by U. prolifera, U. linza, and U. curvata (99.81%). Therefore, it can be concluded that supersaturated seawater due to mass algal bloom caused gas bubble disease in the olive flounder, leading to mass mortality. After technical adjustment, such as increased aeration, lowered water circulation rate, and inlet water filtration using micro-pore carbon filters, the DO level became normal, no further mortality occurred and the status of the fish was stabilized.

• Fisheries and Aquatic Sciences
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• v.4 no.2
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• pp.88-92
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• 2001

To examine effects of cadmium on the respiratory burst of kidney phagocytes and antioxidant defense in liver, juvenile red seabream Pagrus major were fed a cadmium-incorporated diet $(1g\;CdC1_2/kg\;diet)$. The respiratory burst activity measured by chemiluminescence (CL) was significantly reduced by oral intake of cadmium. Lipid peroxidation in liver expressed as thiobarbituric acid reactive substances (TBARS) was significantly higher in the fish fed a cadmium-incorporated diet than that of the fish fed a control diet both on Day 3 and Day 9. Liver Glutathione S-transferase (GST) activitiy was significantly increased both on Day 3 and Day 9 by feeding a cadmium-incorporated diet, when compared with the controls. From the present results, it can be concluded that oral intake of cadmium in red seabream is associated with marked reduction of respiratory burst capacity of kidney phagocytes which can elevate susceptibility of fish against infecting pathogens. Cadmium administration also elicits significant increment of lipid peroxidation in liver, and fish try to detoxify cadmium by increasing GST activity.

• Journal of fish pathology
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• v.35 no.2
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• pp.231-239
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• 2022

In this study, imported ornamental goldfish (Oranda and black moor) with high mortality was investigated with histopathological analysis. Fishes showed clinical symptoms characterized by gill necrosis and cumulative mortality ranging from 60% to 90% within a month after import from Thailand and China in 2021. CyHV-2 was detected in gill, kidney, spleen and liver of goldfishes. Histopathological analysis revealed epithelial necrosis, intranuclear inclusion bodies associated with viral symptoms in epithelial cell, macrophage infiltration and vacuolation in secondary lamella. In addition, disseminated granuloma formation was observed in various organs such as kidney, heart and mesenchymal membranes. These lesions refer to coinfections with CyHV-2 and other pathogens that cause chronic inflammation, which leads to mortality. Therefore, early disease monitoring needs to reduce the mortality when ornamental goldfish is imported.

• Korean Journal of Veterinary Research
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• v.39 no.2
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• pp.365-369
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• 1999

A study on quinolone antibacterial, norfloxacin, was performed to apply for the control of bacterial diseases in eel (Anguilla japonica). Norfloxacin was proved excellent in antibacterial activity and sensitivity against fish bacterial pathogens when compared with the existing antibacterials and antibiotics. And any side effect was not observed during the period of indicated use. An outline of minimal inhibitory concentration was $0.03{\sim}0.1{\mu}g/ml$, $TLm_{48h}$ value was 3,500mg/l. The residual time of the day in fish body was less than 17 days and any pathological changes were not observed. The study has revealed that norfloxacin can be applied to treat some fish bacterial disease by the dosage of 100g/day/ton of fish body weight for about 3 days perorally. Further, norfloxacin may be used for the control of bacterial pathogens in eel.

• Journal of fish pathology
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• v.25 no.3
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• pp.165-172
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• 2012

Vibrio alginolyticus (V. alginolyticus), which is one of bacterial pathogens evoking severe infection in fish and shellfish as well as in human has been found at high frequency around all coast areas in Korea. Both V. alginolyticus and V. alginolyticus specific bacteriophage were isolated from sea water and various fishes from fish farms on west coast in Korea. In a morphological study based on electron microscope, the purified phage appeared to be composed of hexagon head of 60 nm and short tail of 20 nm. In the denatured SDS-PAGE analysis, the structural proteins of the phage were found to be 7 different protein fractions ranging from 37.8 to 198 kda. The kind of nucleic acid of the phage was ascertained to a double stranded DNA.

• Journal of fish pathology
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• v.22 no.3
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• pp.283-291
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• 2009

This study was conducted to evaluate the effects of a commercial extruded pellet (EP) and raw fish moist pellet (MP) diet on disease prevalence and serum chemistry of olive flounder Paralichthys olivaceus grown in two commercial-scale aquaculture farms from July to December in 2008. The contents of serum GOT, GPT and glucose in fish fed EP diet (EP group) were higher than those of fish fed the MP diet (MP group). There were no distinct differences in survival rates and mean detection rates of fish pathogens among fish group fed the experimental diets. However, the mean detection rate of fish pathogens in MP group was higher than that of EP group from July to October which are high water temperature season. The dominant pathogens isolated in EP group were Dactylogyrus sp., E. tarda and red sea bream iridovirus (RSIV). On the other hand, Trichodina sp., Streptococcus spp., viral nervous necrosis virus (VNNV) were dominant in MP group.