• Ocean and Polar Research
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• 제23권3호
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• pp.285-290
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• 2001

The strength of juvenile black rockfish, Sebastes schlegeli, raised in different hatcheries for wild stock enhancement was evaluated in terms of resistance to an anesthetizing agent, tricaine methane-sulfonate (MS-222), and exposure to drying. The working dosage of MS-222 varied significantly with fish size and hatchery population. Smaller fish were less resistant to the chemical than larger ones. MS-222 effects also differed with fish growth history. The fish cultured in embanked populations showed stronger resistance, earlier recovery, and lower mortality, compared to those cultured in land-based tanks or collected from wild stocks. Similar results were seen in juveniles challenged to dry exposure. These results suggest that an embanked population of black rockfish is more resistant to anesthetic stress, expressed as anesthesia recovery and mortality, and that this population is healthier than others.

• 한국어류학회지
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• 제29권1호
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• pp.75-79
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• 2017

본 연구에서는 2014년 제주도에 위치한 양식장에서 해수로 사육 중인 무지개송어에서 만성질병으로 인해 약 10%의 누적 폐사가 발생하였다. 병어는 복부가 팽만되어 있었고 위가 심하게 팽창되어 있었다. 질병 검사 결과, 기생충, 세균, 바이러스는 검출되지 않았으나 팽창된 위에서 다수의 Candida sp.가 분리되었다. Candida sp.를 사용하여 감염 실험을 실시한 결과, 대부분 개체에서 폐사가 발생하지 않았고 위 팽창 증상이 관찰되지 않아 Candida sp.는 본 질병의 원인 병원체가 아닌 것으로 사료되었다. 본 연구에서는 국내에서 처음으로 해수 사육 무지개송어에서 위팽창증후군이 발생하는 것을 확인하였다.

• 한국수산과학회지
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• 제54권5호
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• pp.596-616
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• 2021

A global increase in fish consumption has led to a rapid expansion of aquaculture production, which has been linked to enhancing the spread of infectious diseases. Viral diseases can cause high mortality in many cultured fish species, posing a serious threat to the aquaculture industry. Infectious hematopoietic necrosis virus (IHNV) is one of the primary threats to aquacultured salmonid species, causing huge economic losses. Since the first report in cultured sockeye salmon Oncorhynchus nerka during the 1950s in North America, IHNV has spread to other regions, including Europe, Asia, South America, and Africa by transportation of infected fish and eggs, causing disease and increasing mortality in a wide variety of salmonid species. Here, we review existing information relevant to IHNV: its phylogenetic characteristics, origin, infection history, virulence determinants, susceptible hosts, vectors, and vaccine development. This review also addresses a possible cross-species transmission of IHNV to a new host, olive flounder Paralichthys olivaceus, a cultured fish of economic importance in East Asian countries.

• 한국어병학회지
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• 제34권1호
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• pp.1-7
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• 2021

Red sea bream iridovirus (RSIV), belonging to the genus Megalocytivirus, is the predominant cause of mortality in marine fishes in Korea, including rock bream (Oplegnathus fasciatus). Rockfish (Sebastes schlegelii) are the host fish for RSIV, exhibiting no clinical signs or mortality. Cohabitation challenges, which mimicked natural transmission conditions, were performed to evaluate viral transmission between rock bream and rockfish, and to determine the pathogenicity and viral loads. In cohabitation challenge, artificially RSIV-infected rock bream were the viral donor, and healthy rockfish were the recipient. The results showed that although the donor rock bream had 95-100 % cumulative mortality (>10⁸ viral genome copies/mg of spleen 7-14 days after viral infection), the recipient rockfish did not die, even when the viral genome copies in the spleen were >10⁵ copies/mg. These results indicated asymptomatic infections. Notably, in a reverse-cohabitation challenge (artificially RSIV-infected rockfish as the viral donor and healthy rock bream as the recipient), RSIV horizontally infected from subclinical rockfish to rock bream (10⁷ viral genome copies/mg of spleen 21 days after cohabitation) with 10-20% cumulative mortality. These results suggest that an asymptomatic, infected rockfish can naturally transmit the RSIV without being sacrificed.

• 한국어병학회지
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• 제36권2호
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• pp.213-228
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• 2023

We evaluated the transcriptional response of interferon (IFN)-related genes in rock bream iridovirus (RBIV)-infected rock bream under high-, low-, or no-mortality conditions induced by different stocking water temperatures. Under the high susceptibility condition (group A, water temperature 26℃, 100% mortality), only the Mx gene was expressed early, with prolonged expression, and with heavy viral loads of approximately 10⁶~10⁷ major capsid protein gene copies/μL from 4 to 10 days post infection (dpi). However, IRF1, IRF3, IRF8, STAT1, ISG15, PKR, Viperin, GVIN1, IFI44, and ISG56 were activated at later time points (8 dpi) and then quickly decreased (10 dpi). For the low susceptibility condition, the water temperature was set at 23℃ for 7 days (group B) and then reduced to 17℃. Group B exhibited a 28% mortality rate, in which persistent and effective antiviral responses were observed for long periods of time. In particular, at 20 and 22 dpi, when virus replication was peaked at approximately 10⁷/μL, the expressions of most of the IFN-related genes (IRF1, IRF3, IRF8, Mx, STAT1, ISG15, PKR, Viperin, GVIN1, IFI44, and ISG56) were significantly higher in group B than in the control group. Moreover, prolonged and higher levels of IRF3 (at least 30 dpi), IRF8 (at least 30 dpi), ISG15 (at least 30 dpi), PKR (at least 28 dpi), Viperin (at least 30 dpi), and IFI44 (at least 30 dpi) were also observed in the recovery stage of infection. Under the no-susceptibility condition at 17℃ (0% mortality), significantly elevated levels of IRF3, Mx, ISG15, and PKR were observed mostly until 20 dpi. The findings indicate that RBIV infection can induce an efficient IFN-mediated antiviral immune response in low- and no-susceptibility conditions. The findings could be valuable for effective control of viral pathogens in fish.

• Journal of Microbiology and Biotechnology
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• 제25권10호
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• pp.1761-1767
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• 2015

Sevenband grouper, Epinephelus septemfasciatus, is becoming an important aquaculture species in Korea. However, viral nervous necrosis disease is a large problem causing mass mortality in sevenband grouper aquaculture. Recombinant protein vaccines are one of the best methods to reduce these economic losses. However, the cell-based expression method mainly produces inclusion bodies and requires additional procedures. In this study, we expressed a recombinant viral coat protein of sevenband grouper nervous necrosis virus (NNV) using a cell-free protein synthesis system. The purified recombinant NNV coat protein (rNNV-CP) was injected into sevenband grouper at different doses followed by a NNV challenge. Nonimmunized fish in the first trial (20 μg/fish) began to die 5 days post-challenge and reached 70% cumulative mortality. In contrast, immunized fish also starting dying 5 days postchallenge but lower cumulative mortality (10%) was observed. Cumulative morality in the second trial with different doses (20, 4, and 0.8 μg/fish) was 10%, 40%, and 50%, respectively. These results suggest that rNNV-CP can effectively immunize sevenband grouper depending on the dose administered. This study provides a new approach to develop a recombinant vaccine against NNV infection for sevenband grouper.

• 한국어병학회지
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• 제21권1호
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• pp.13-20
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• 2008

본 연구에서는 RSIV의 수온에 따른 병원성을 규명하기 위한 연구의 일환으로 수온별로 RSIV를 인위적으로 감염시킨 돌돔의 누적폐사를 관찰하고, 다른 온도에서 사육된 돌돔의 온도 스트레스 단백질인 HSP이 관여하는지를 확인하고자, 돌돔의 HSP 유전자의 염기서열 일부를 밝혔다. 각온도별 감염실험에서 17°C와 20°C의 경우 폐사가 발생하지 않았으나, 25°C 및 27°C 수조에서는 각각 90%와 80%의 누적 폐사율을 보였다. 돌돔에서 확인된 HSP 유전자의 일부는 넙치에서 확인된 HSP70와 97%의 homology를 나타내 돌돔의 HSP70으로 판단되었다.

• 한국어병학회지
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• 제32권1호
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• pp.29-35
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• 2019

2015년부터 2017년까지 우리나라 넙치 양식장에서 발생하는 폐사피해를 표본조사를 통해 모니터링 하였다. 표본어가는 전국의 수산질병관리원과 지속적으로 거래하고 있으며 현장방문을 통해 설문이 가능한 양식어가 중 층화구조분석을 통해 선정 하였다. 수산질병관리사 조사요원의 직접적인 현장방문을 통한 설문 조사를 수행하여 객관적으로 양식현황 및 폐사 현황을 파악하였다. 조사기간 중 24.78%/2015년, 30.19%/2016년 그리고 21.59%/2017년의 누적 폐사율을 나타내었고, 감염성 질병에 의한 폐사는 스쿠티카증(2015-2017년 평균 누적 폐사율: 56.7%)과 바이러스성출혈성 패혈증 감염(추정)(2015-2017년 평균 누적 폐사율: 8.9%)에 의한 피해가 높은 것으로 나타났으며, 제주에서는 여윔증(2016-2017년 평균 누적 폐사율: 10.3%)에 의한 피해가 높게 나타났다.

• 한국어병학회지
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• 제34권1호
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• pp.99-104
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• 2021

In this study, we investigated safety and efficacy of a low temperature immunization protocol with NNV in red spotted grouper, Epinephelus akaara and long tooth grouper, Epinephelus bruneus and seven band grouper, Hyporthodus septemfasciatus. Further, growth rate between immunized and naïve fish was evaluated during the experiment to check side effect of immunization. Three grouper species were immunized by immersion method with live NNV at 10^5.0 TCID₅₀/mL at 16.5℃ for 30 min and reared for 120 days at natural sea water temperature. To evaluate growth rate, total length and wet weight was measured 7 times after immunization. Immunized three grouper species were challenged by intramuscular inoculation with NNV at 10^4.2 TCID₅₀/100 µL/fish. Immunization at low temperature with live NNV did not show any clinical symptoms of infection, mortality and inhibition of growth. After challenge, cumulative mortality of naïve seven band grouper, red spotted grouper, long tooth grouper were 45, 10, 20 %, respectively. However no mortality was observed at immunized groupers. Thus, it was demonstrated that immunization at low temperature with live NNV are able to protect three different species of groupers without inhibition of growth.

• 한국수산과학회지
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• 제45권6호
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• pp.606-611
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• 2012

This study examined the effects of dietary glycoprotein extracted from Porphyra yezoensi on growth performance and resistance against the pathogenic bacteria Edwardsiella tarda in olive flounder. A porphyra-originated glycoprotein (P) was extracted using sequential processes of water and ethanol treatment. P extracts were added to a fish-meal-based diet at concentrations of 0.0, 0.5, and 1.0% (designated as Con, $P_{0.5}$, and $P_{1.0}$, respectively). Fish were fed one of the three experimental diets for 10 weeks. All fish groups exhibited over 96.7% survival during the experimental period. Results indicated that the fish fed diets containing P showed an increase in growth performance, including enhanced weight gain, specific growth rate, and feed efficiency. An increase in insulin-like growth factor (IGF-1) was observed in the fish fed the $P_{1.0}$ diet, as compared to those fed Con. At the end of the 10-week feeding trial, all fish were infected with E. tarda, and accumulated mortality was monitored for 8 days. Fish fed the Con diet exhibited increasing mortality from day 3 to the end of the challenge test, whereas the mortality of P-fed fish ceased at day 5. We suggest that supplementation with P-originated glycoprotein in aquafeed may increase growth performance and resistance against pathogenic bacteria in olive flounder juveniles.