• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.585-595
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• 2021

Even though most of aquatic animal pathogens are considered opportunistic and many pose a low direct risk to personnel, all personnel working with aquatic pathogens and facilities using these organisms must comply with the regulation to prevent the release of the pathogen into the environment and causing disease in aquatic animals. First of all, in order to establish a biosafety system for aquatic pathogen, the list of microorganisms that can infect aquatic animals and humans should be drawn up according to the microorganisms encountered within national boundaries. Second, risk assessment guideline for diseases of livestock and aquatic environment is desperately needed. Third, microorganisms should be classified into risk group based on their potential impact on human and aquatic environment. Fourth, facilities handling aquatic pathogens should ensure that these pathogens are securely contained and safely handled for experimental or commercial development purposes. In conclusion, classification is based on the pathogenicity, mode of transmission and host range of the aquatic microorganisms, availability of effective preventative measures and treatments. Furthermore, risk group of aquatic pathogens should be correlated with physical containment facility requirements according to domestic characteristics.

• Journal of fish pathology
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• v.33 no.1
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• pp.97-101
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• 2020

Although aquaculture production rates grown over the years, aquatic animal diseases occur every year which causes substantial economic losses. When an aquatic animal is infected with an aquatic animal pathogen it is either incinerated or buried according to the aquatic life disease control act. Although these methods prevent the spread of disease, it is not environment friendly. Here, we developed an aquatic animal rendering equipment for disposal of fish waste which is environment-friendly and efficient. Also, fertilizer components of fish waste were evaluated value for recycling. The mobile rendering equipment was designed for field operation and/or high temperature and pressure system, oil and water separator, and shredding drying apparatus. During the experiment (July-2016 to November-2016), a total of 53,824 kg fish waste was collected, and 29,216 kg compost of rendering by-product was made. Also, compost made from viral (Viral hemorrhagic septicemia virus) infected fish did not reflect any detectable pathogen. The concentration of nitrogen, phosphorus, and organic matter in the fish waste compost were 2.17%, 26.98%, and 92.44%, respectively. The results suggest that fish waste used in this study was decomposed efficiently as per the official standard for fertilizer product. This equipment can be useful for efficient inactivation of the aquatic animal pathogenic agents and recycling of the fish waste in an environment-friendly manner.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.450-455
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• 2018

We examined correlations of the density of fish farms with the distributions of indicator bacteria (Escherichia coli, fecal streptococci) and a bacterial fish pathogen (Streptococcus parauberis) off the coastline of Jeju Island. Seawater samples were collected at four coastal sites on the Island [Aewol (control), Gujwa, Pyoseon and Daejeong] in June, August and October 2016. The indicator bacteria were generally more frequently isolated from samples taken in August when water temperatures and human activities on nearby beaches were highest. Although fish farms were least common at Daejeong, the numbers of isolated fecal indicator bacteria were highest in the seawater and effluent water collected from this site. Hence, fish farms were not likely major contributors of indicator bacteria at Daejeong. We found discrepancies between the isolated bacterial counts and the predicted bacterial copy numbers deduced from our qPCR results, indicating that this pathogen may exist in a viable but non-culturable (VBNC) state in seawater. Thus, livestock wastewater and chemical fertilizer loading off Jeju Island may negatively impact seawater quality more than the effluent released from fish farms does.

• Korean Journal of Veterinary Research
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• v.57 no.1
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• pp.67-69
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• 2017

In the present study, Aeromonas (A.) hydrophila was isolated from a captive-bred adult freshwater stingray (Potamotrygon motoro) reared at a commercial aquarium in Korea. The stingray had bites on its fins, hemorrhages on the ventral part, and congested internal organs. A bacterium was isolated from kidney and subsequently identified as A. hydrophila. Based on phylogenetic analysis results, the isolate in the present study (SNUAh-LA1) was most closely related to A. hydrophila AH10 (China) and A. hydrophila AKR1 (Korea). It is most likely that the pathogen infection resulted from Potamotrygon motoro cohabiting with ricefish (Oryzias latipes).

• ALGAE
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• v.32 no.2
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• pp.155-160
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• 2017

Red rot disease has caused a major decline in Pyropia (Nori) crop production in Korea, Japan, and China. To date, only Pythium porphyrae (Pythiales, Oomycetes) has been reported as the pathogen causing red rot disease in Pyropia yezoensis (Rhodophyta, Bangiales). Recently, Pythium chondricola was isolated from the infected blades of Py. yezoensis during molecular analyses using the mitochondrial cox1 region. In this study, we evaluated the pathogenicity of P. chondricola as an algal pathogen of Py. yezoensis. Moreover, a new cox2 marker was developed with high specificity for Pythium species. Subsequent to re-inoculation, P. chondricola successfully infected Py. yezoensis blades, with the infected regions containing symptoms of red rot disease. A novel cox2 marker successfully isolated the cox2 region of Pythium species from the infected blades of Py. yezoensis collected from Pyropia aquaculture farms. cox2 sequences showed 100% identity with that of P. chondricola (KJ595354) and 98% similarity with that of P. porphyrae (KJ595377). The results of the pathogenicity test and molecular analysis confirm that P. chondricola is a new algal pathogen causing red rot disease in Pyropia species. Moreover, it could also suggest the presence of cryptic biodiversity among Korean Pythium species.

• Journal of fish pathology
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• v.37 no.1
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• pp.49-60
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• 2024

A viable but non-culturable (VBNC) state is a survival strategy adopted by bacteria when faced with unfavorable environmental conditions, rendering them unable to grow on nutrient agar while maintaining low metabolic activity. This study explored the impact of temperature and nutrient availability on inducing VBNC state in Edwardsiella piscicida, the most important bacterial fish pathogen, and assessed its pathogenicity at VBNC state. E. piscicida was suspended in filtered sterile seawater and exposed to three different temperatures (4, 10, and 25℃) to induce the VBNC state. Subsequently, the induced VBNC cells were subjected to resuscitation by either raising the temperature to 28℃ or inoculating them in brain heart infusion broth supplemented with 1% NaCl. A propidium monoazide (PMA)-qPCR method was also developed to selectively quantify live (VBNC or culturable) E. piscicida cells. The results showed that the bacteria entered the VBNC state after approximately 1 month at 4℃ and 25℃, and 2 months at 10℃. The VBNC E. piscicida cells were successfully revived within 3 days in a nutrient-rich environment at 28℃, highlighting the significance of temperature and nutrition in inducing and resuscitating the VBNC state. In pathogenicity tests, resuscitated E. piscicida cells exhibited high pathogenicity in olive flounder comparable to cultured bacteria, while VBNC cells showed no signs of infection, suggesting they are unlikely to resuscitate in fish. In conclusion, this study contributes to our understanding of fish pathogen ecology by investigating the characteristics of the VBNC state under varying temperature and nutrition conditions.

• Fisheries and Aquatic Sciences
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• v.19 no.4
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• pp.18.1-18.10
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• 2016

In this study, to clarify the function of $PoPLC-{\beta}1$, in response to stress challenge, we examined the $PoPLC-{\beta}1$ expression pattern in response to external stress (pathogen-associated molecular pathogen challenge and environmental challenge including temperature and salinity). $PoPLC-{\beta}1$ expression analysis of tissue from olive flounder showed that the messenger RNA (mRNA) was predominantly expressed in the brain, heart, eye, liver, spleen, and stomach. We also tested the mRNA expression of the $PoPLC-{\beta}1$ in the spleen and kidney of olive flounder by RT-PCR and real-time PCR following stimulation with lipopolysaccharide (LPS), concanavalin A (ConA), or polyinosinic:polycytidylic acid (PolyI:C) and compared with the inflammatory cytokines IL-1b and IL-6 in the stimulated flounder tissues. Each of the spleen and kidney and mRNA transcripts of $PoPLC-{\beta}1$ were increased 30- and 10-fold than normal tissue at 1-6 h post injection (HPI) with PolyI:C when the expression of $PoPLC-{\beta}1$ transcript was similar to LPS and ConA. We also tested the expression of $PoPLC-{\beta}1$ in response to temperature and salinity stress. The expression of $PoPLC-{\beta}1$ also was affected by temperature and salinity stress. Our results provide clear evidence that the olive flounder $PLC-{\beta}1$ signal pathways may play a critical role in immune function at the cellular level and in inflammation reactions. In addition, $PLC-{\beta}1$ appears to act as an oxidative-stress suppressor to prevent cell damage in fish.

• ALGAE
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• v.30 no.3
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• pp.217-222
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• 2015

Pythium species (Pythiales, Oomycetes) are well known as the algal pathogen that causes red rot disease in Pyropia / Porphyra species (Bangiales, Rhodophyta). Accurate species identification of the pathogen is important to finding a scientific solution for the disease and to clarify the host-parasite relationship. In Korea, only Pythium porphyrae has been reported from Pyropia species, with identifications based on culture and genetic analysis of the nuclear internal transcribed spacer (ITS) region. Recent fungal DNA barcoding studies have shown the low taxonomic resolution of the ITS region and suggested the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene as an alternative molecular marker to identify Pythium species. In this study, we applied an analysis of both the ITS and cox1 regions to clarify the taxonomic relationships of Korean Pythium species. From the results, the two closely related Pythium species (P. chondricola and P. porphyrae) showed the same ITS sequence, while the cox1 marker successfully discriminated P. chondricola from P. porphyrae. This is the first report of the presence of P. chondricola from the infected blade of Pyropia yezoensis in Asia. This finding of the algal pathogen provides important information for identifying and determining the distribution of Pythium species. Further studies are also needed to confirm whether P. chondricola and P. porphyrae are coexisting as algal pathogens of Pyropia species in Korea.

• Mycobiology
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• v.44 no.2
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• pp.85-92
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• 2016

Mycoherbicides are exclusive biotechnology products which offer a non-chemical solution to control noxious weeds on the land as well as aquatic in systems, viz a viz saving environment from hazardous impact of synthetic chemicals. The present paper highlights the mycobiota associated with Eichhornia crassipes infesting Harike wetland area of Punjab and evaluation of their pathogenic potential for futuristic application as a mycoherbicide. Of the 20 isolates tested by leaf detached assay and whole plant bioassays, only one isolate (#8 BJSSL) caused 100% damage to E. crassipes. Further, the culture filtrate of this isolate also exhibited a similar damage to the leaves in an in vitro detached leaf assay. The potential isolate was identified as Phaeoacremonium italicum using classical and modern molecular methods. This is the first report of P. italicum as a pathogen of E. crassipes and of its potential use as a biological control agent for the management of water hyacinth.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.654-658
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• 2012

Vibrio alginolyticus, a marine fish and shellfish pathogen, has been found at a high frequency around the coastal areas of Korea. Vibrio alginolyticus was purified from various diseased fish, and a V. alginolyticus-specific bacteriophage was isolated from seawater obtained from fish farms located on the west coast of Korea. In a bacterial lysis experiment using the phage and antibiotics, tetracycline, $10^3$ cfu/ml of V. alginolyticus were completely lysed by both the phage and the antibiotic, suggesting that the purified phage in the study could be utilized as an alternative to antibiotics in the control of fish and shellfish diseases caused by V. alginolyticus.