• Journal of fish pathology
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• v.20 no.2
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• pp.99-108
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• 2007

Vibrio harveyi, one of the major causal agent of vibriosis, affects a diverse range of marine vertebrates and invertebrates over a wide geographical area. The organism is synonymous with Vibrio carchariae, which is also known as a fish pathogen. The aims of this study were to investigate the characteristics of the pathogenic non-luminous V. harveyi and the luminous V. harveyi. And V. harveyi isolates were examined the pathogenicity to the black rockfish, Sebastes schlegeli. Both strains of V. harveyi showed haemolytic activity, and the survival rate of non-luminous V. harveyi FR 2 was higher than other strains in the skin, gut mucus and fresh serum of olive flounder, Paralichthys olivaceus and black rockfish, Sebastes schlegeli, respectively. The virulence of non-luminous V. harveyi FR 2 was higher than that of luminous V. harveyi VIB 391 in the intraperitoneally infected black rockfish. In conclusion, the present study revealed that the pathogenicity of V. harveyi FR 2 isolated from marine fish was higher than that of V. harveyi VIB 391 isolated from shrimp for black rockfish. It was suggested that the pathogenicity of V. harveyi on the black rockfish was related with bacterial luminescense.

• Journal of fish pathology
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• v.27 no.1
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• pp.47-56
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• 2014

Propolis is a beehive product with a very complex chemical composition, widely used in folk medicine because of its several therapeutic activities. This study was conducted to measure the efficacy of propolis on non-specific defense reactions, specific immune response, and protection levels against pathogen challenge with Streptococcus iniae. in vitro and in vivo. In vitro, the phagocytic activity and NBT assay of peripheral blood leukocytes (PBL) were evaluated in a various propolis extractsconcentrations (0, 10, 50, 100, 150, 250 and $500{\mu}g/ml$). The optimal concentration showing activation of propolis extracts was determined to $100{\mu}g/ml$. In vivo, they were divided into four groups (PBS, propoli extractss, vaccine, propolis extracts + vaccine) in vivo. Fish were received i.p. injection of either PBS or propolis extracts, and in the presence or absence of formalin inactivated S. iniae ($1{\times}10^8$ CFU/fish), respectively. The level of haematocrit is not affected among experimental groups. The phagocytic activity and the NBT reduction activities of head kidney phagocyte were markedly (p<0.05)augmented in the propolis extracts groups than in the PBS-control group, respectively. The level of serum lysozyme activity was significantly (p<0.05) increased in the propolis extracts treated groups than in the PBS-control group. The agglutinin titer was significantly (p<0.05) enhanced in the vaccine+propolis extracts group than in the vaccine group, but there was no difference between PBS-control and propolis treated group. The results of the present study suggest that propolis extracts seems to be a promising compounds of non-specific immune stimulator, also being able to use a good adjuvant.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.3
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• pp.432-442
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• 2020

Diagnostic monitoring in Korean rockfish cages was performed to survey the prevalence of pathogens in cultured Korean rockfish Sebastes schlegeli from May 2013 to July 2016. A total of 1,945 fish samples collected from the western (Cheonsu Bay and Heuksando), southern (Tongyeong and Namhae), and eastern coasts (Pohang) of Korea were tested for parasites, viruses, and bacteria. In this study, 1,264 and 334 fishes were infected with Microcotyle sebastis and Clavinema mariae, respectively. The prevalence rates of C. clavinema in fishes from Cheonsu Bay, Heuksando, and Tongyeong were 35.3%, 3.9% and 1.9%, respectively. No C. clavinema infection was detected in cultured rockfish from Namhae and Pohang. Furthermore, bacteria including Photobacterium damselae (8.9%), Photobacterium piscicola (2.3%), Photobacterium spp. (8.9%), Aeromonas salmonicida (1.8%), Aeromonas spp. (0.9%), Vibrio scophthalmi (1.5%), Vibrio spp. (3.3%), Streptococcus iniae (1.2%), and others (8.0%) were detected in 373 of 1,364 fishes. No virus was detected in any fish investigated in this study.

• Korean Journal of Veterinary Research
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• v.38 no.2
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• pp.371-378
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• 1998

Five strains of gram-negative and yellow-pigmented bacteria were recently isolated from diseased freshwater fishes in Korea. All isolates were confirmed as a known fish pathogen of columnaris disease, Cytophaga columnaris based on their colonial and cellular morphology, and on physiological, biochemical and antigenic characteristics. Although the isolates were from different fish species, their characteristics of them were very similar to those of the reference strains of C columnaris (NCMB $2248^T$ and EK 28). Also, profiles of OMPs of Korean isolates were similar to those of the reference strain, C columnaris NCMB $2248^T$ when analyzed by SDS-PAGE.

• Journal of fish pathology
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• v.22 no.3
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• pp.239-251
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• 2009

The effects of microbiological properties and pathogenicity of Photobacterium damselae subsp. damselae were investigated under different culture conditions, temperature, pH, NaCl and iron concentration on culture media. Favorable conditions for bacterial growth were between 15-30${^{\circ}C}$, pH 5-9, 0-4% NaCl concentration and iron contents of over 10 mM, whereas the bacterial growth was inhibited under iron chelator existence. When P. damselae was cultured in iron-limited tryptic soy broth, total protein concentration of extracellular products, cytotoxic ability of ECPs on cell line, bacterial viability in flounder serum, phospholipase and siderophore activities of ECPs were significantly increased. On the other hand, the activities of P. damselae cultured under iron-added conditions were decreased. In this study, the iron-limited conditions were similar to the host in which iron concentration is low. During infection caused by P. damselae, the conditions could be related to the pathogenesis of the pathogen.

• Journal of fish pathology
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• v.28 no.1
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• pp.1-7
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• 2015

In 2009 outbreaks of an emerging disease in shrimp farms were first reported in China. The disease was known as early mortality syndrome (EMS), or acute hepatopancreatic necrosis disease (AHPND). Since 2009, the disease has been spread to Vietnam, Malaysia, Thailand and Mexico. The causative agent of the disease was identified as Vibrio parahaemolyticus. It is a common seawater inhabitant bacterium, and the pathogen can sometimes contaminate seafood. The disease has caused mass mortality of cultivated shrimp, and huge economic losses in the countries named above. In order to prevent the introduction and establishment of AHPND, emergency measures, such as strengthening of import conditions and even import bans, were put in place by many other countries. In Korea, on the other hand, there are large quantities of shrimp imports from countries, such as Thailand and Vietnam. Transportation of live and fresh dead shrimp is highly likely, and could be a transmission pathway if the shrimp are sourced from populations in AHPND endemic areas. It is important to recognize that importing countries may provisionally adopt sanitary or phytosanitary measures on the basis of available pertinent information, including that from the relevant international organizations, as well as from sanitary or phytosanitary measures applied by other countries based on "Agreement on Application of Sanitary and Phytosanitary Measures". It is pertinent that Korea also takes proper emergent measures to keep out diseases and provide safe seafood.

• Journal of Aquaculture
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• v.10 no.2
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• pp.171-178
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• 1997

Infectious pancreatic necrosis virus (IPNY) is an economically important fish pathogen since it causes the high-mortality disease in early stage of hatchery-reared fishes. In order to develop a rapid, sensitive and highly specific detection method for IPNV, reverse transcription-polymerase chain reaction (RT-PCR) was carried out using the oligonucleotide primers selected from the sequence of VP2, a major capsid polypertide of IPNV. As little as 40ng of purified IPNV dsRNA was detected by RT-PCR amplification, but no amplification products were obtained when nucleic acid genomes from other fish pathogens such as IHNV were used as RT-PCR templates. in situ RT-PCR methods are useful for the rapid and sensitive identification of IPNV.

• Korean Journal of Organic Agriculture
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• v.19 no.spc
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• pp.39-42
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• 2011

This experiment was conducted to evaluate the effect of two different organic acid products as antibiotic replacement in olive flounder paralichthys olivaceus. Fish averaging $3.5{\pm}0.05$ g($mean{\pm}SD$) were fed one of the ten semi-purified diets : Diet 1 ; Control, Diet 2 ; add antibiotics - 50mg OTC/kg body weight/day(OTC), Diet 3 ; Add organic acid bland A(OABA) - 4g/kg diet, Diet 4 ; add organic acid bland B(OABB) - 4g/kg diet for 10 weeks. Total gut microflora counts were significantly higher in the control group compared to the OTC and organic acid groups(P<0.05). Fish fed OABA, OABB and OTC had lower gut Vibrio counts compared to the control, but were not significantly different. Results from the challenge study indicate that mortality in the different treatment groups (50%) was significantly lower than those observed for the control group (100%). There were no differences in mortality between the OTC and organic acid groups. Overall findings from this study indicate that the organic acid blends A and B were as effective as oxytetracycline, an antibiotic, in regulating total gut bacterial numbers, Vibrio counts and providing protection against a pathogen such as Edwardsiella tarda.

• Journal of fish pathology
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• v.34 no.1
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• pp.31-38
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• 2021

The objective of this study was to determine comparative biochemical characteristics and RAPD (random amplified polymorphic DNA) profiles of 18 strains of Edwardsiella tarda isolated from cultured olive flounder (Paralichthys olivaceus) and eel (Anguilla spp) that showed diseases between 1996 and 2010 in Korea. In terms of biochemical properties, they showed four patterns with differences in citrate degradation and production of H₂S and indole. All strains were identified as E. tarda. Characteristics of isolates were not classified according to their host. As a result of PCR with E. tarda-specific primer, EDtT, the same band of about 270 bp was detected in all 18 isolates. However, no specific band was detected in type strains of E. tarda or Edwardsiella ictaluri. As a result of RAPD PCR performed with primer No. 5 and No. 6 of a Ready-To-Go-RAPD kit, the band profile showed clear differences among isolates of olive flounder, isolates of eel, and E. tarda and E. ictaluri type strains. It was possible to organize their characteristics according to the origin of host with possibility to develop tools for pathogen monitoring.

• Fisheries and Aquatic Sciences
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• v.25 no.6
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• pp.320-326
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• 2022

Most of the emerging diseases that threaten humans are caused by RNA viruses which are extremely mutable during evolution. The fish RNA virus, viral hemorrhagic septicemia virus (VHSV) can infect a broad range of aquatic animal hosts, but the transmissibility of VHSV to mammals has not been thoroughly investigated. Therefore, our study aimed to investigate the potential adverse effects of VHSV in mammals. Briefly, the survival of VHSV was determined using only minimum essential media (MEM-2) and mammalian SNU-1411 and hepa-1c1c7s cells at 15℃ and 37℃. Mice (Mus musculus, 27.3 ± 1.9 g) were intravenously injected with VHSV (2.37E+05 TCID₅₀·mice^-1) in triplicate. Clinical signs and survival rates were examined at 14 days post-challenge, and infection was confirmed in the surviving mice. The 50% tissue culture infective dose (TCID₅₀) and polymerase chain reaction analysis were used to determine viral titers and the infection rate, respectively. The titer of VHSV suspended in MEM-2 at 15℃ was reduced by only one log after 8 days, whereas the virus maintained at 37℃ was inactivated 8 days post-inoculation (dpi). There were no recognizable cytopathic effects in either SNU-1411 or hepa-1c1c7s cells inoculated with VHSV at 15℃ and 37℃. VHSV in those cell lines at 37℃ was rapidly decreased and eventually inactivated at 12 dpi, whereas virus at 15℃ remained at low concentrations without replication. In vivo experiment showed that there were no signs of disease, mortality, or infection in VHSV-infected mice. The results of this study indicate that it is highly unlikely that VHSV can infect mammals including humans.