• Journal of fish pathology
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• v.30 no.1
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• pp.1-9
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• 2017

This study was conducted to monitor the prevalence of viral hemorrhagic septicemia virus (VHSV), nervous necrosis virus (NNV) and marine birnavirus (MABV) in cultured walleye pollock Gadus chalcogrammus by RT-PCR. All of the viruses tested were not detected by one-step PCR in 62 spleen sample sets, except for NNV in one brain sample set (1/55). By two-step PCR, VHSV was detected in 51.6%(32/62) and NNV was detected in 1.6%(1/62) spleen sample set, but MABV was not detected. In the brain sample sets, the detection rate of NNV was 3.6%(2/55). VHSV and NNV were detected for the first time in cultured walleye pollock in this study. However, the titers of viruses in these sample sets are thought to be very low, because most of the positive sample sets were detected by two-step PCR and none of the fish showed any clinical symptoms of each virus. Continuous monitoring, subsequent virus isolation and validation of carrier fish will be necessary.

• Journal of fish pathology
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• v.31 no.2
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• pp.71-79
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• 2018

Wild walleye pollock were caught from Goseong, The East Sea of Korea and examined for the existence of several fish pathogenic viruses; viral hemorrhagic septicemia virus (VHSV), nervous necrosis virus (NNV) and marine birnavirus (MABV). We collected 1,253 wild walleye pollock in total during February 2015 and August 2018. 324 spleen sample sets and 259 brain sample sets were made, and examined for the existence of the viruses mentioned above by reverse transcriptase polymerase chain reaction (RT-PCR). None of the target viruses were detected by one-step PCR. When some of these samples were further examined by two-step PCR, 19.7% (36/183) of spleen sample sets were positive for VHSV, and 4.4% (8/183) of spleen sample sets and 1.2% (3/259) of brain sample sets were positive for NNV. The target sequences of these viruses were clustered with those previously reported in Korea (Genotype IVa of VHSV, RGNNV genotype of NNV) by phylogenetic analysis. The activity of these viruses are not clear because virus isolation was not attempted, but probably very low because all the positive samples were detected by two-step PCR.

• Journal of fish pathology
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• v.10 no.2
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• pp.165-176
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• 1997

Water samples collected from marine fish culture system in Korea were compared for their capability to reduce the infectivity titers of HRV (rhabdovirus olivaceus), FBV(flounder birnavirus) and RVS(retrovirus of salmonid). In addition, interaction between viruses and microorganisms present in the rearing seawater was examined. The titer of HRV and RVS were reduced at $15^{\circ}C$ to less than detectable limits within 3 to 5 days using untreated samples of seawater. No reduction of infectivity was noted in bacteria-free water treated by filtration or autoclaving. Bacteria (Pseudomonas and Vibrio sp.) isolated from the water collected from a flounder culture system showed the inactivation activity of HRV.

• Korean Journal of Veterinary Research
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• v.48 no.3
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• pp.287-293
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• 2008

The cDNA of the aquabirnavirus, GC-1 isolated from rockfish Sebastes schlegeli in Korea, was synthesized using the reverse transcriptase-polymerase chain reaction. The nucleotide and deduced amino acid sequences were determined from cDNA of the VP2-NS-VP3 coding region of genome segment A. The nucleotide sequences of the segment A were 3,086 base pairs (bp) in length and contained large open reading frame (ORF) and terminal sequences. The large ORF was comprised of 2,916 bp nucleotides and composed of 972 deduced amino acid sequences. Pairwise comparisons were made with other aquabirnavirus sequences published previously. The study of genetic relationships between GC-1 and aquabirnaviruses in the large ORF and VP2 coding regions demonstrated that the GC-1 has the nearest genetic relationship with the marine birnaviruses (MABV strains), and the GC-1 and MABV strains can be clustered as the same genogroup. GC-1 can be included in MABV, which is the 7th genogroup of family Aquabirnaviridae.

• Journal of fish pathology
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• v.16 no.3
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• pp.165-173
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• 2003

A stable cell line, BSBS (black seabream spleen), was established from the cells in spleen of black seabream, Acanthopagrus schlegeli, and characterized. Subculture maintained more than 60 passages and mophologically, BSBS cell was epithelioid cell. The cells grew optimally at 20℃ in Leibovitz's L-15 medium supplemented with 10% fetal bovine serum with incubation temperature of 20℃. BSBS cells supported the growth of marine birnavirus (MABV Y-6), chum salmon reovirus (CSV), spring viremia of carp virus (SVCV) and hirame rhabdovirus (HIRRV). Thus, the new cell line may be useful for studying wide range of fish viruses.

• Journal of fish pathology
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• v.30 no.2
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• pp.149-154
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• 2017

Mouse monoclonal antibodies (MAbs) were produced by using viral hemorrhagic septicemia virus (VHSV, genotype IVa) as an immunogen, isolated from diseased olive flounder (Paralichthys olivaceus). Four hybridoma clones secreting MAbs against VHSV were established. The MAbs were recognized the nucleoprotein (MAb 4), phosphoprotein (MAb 1) and matrix protein (MAbs 2 and 3) of VHSV by western blot analysis. Among them, the MAbs 1 and 4 strongly reacted with the VHSV-infected FHM cells, but not normal FHM cells. In enzyme linked immunosorbent assay, the four MAbs reacted with the VHSV, but not different six fish viruses (infectious hematopoietic necrosis virus, hirame rhabdovirus, spring viraemia of carp virus, infectious pancreatic necrosis virus, marine birnavirus and nervous necrosis virus). These results indicate that the MAbs are useful for diagnosis of VHSV infection.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.328-331
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• 2018

We developed and subsequently characterized mouse monoclonal antibodies (MAbs) against nervous necrosis virus (NNV, RGNNV genotype). We established six hybridoma clones secreting MAbs against NNV antigen: 2B1, 2B11, 2C12, 13C1-1, 13C1-2 and 14D11. All six MAbs belonged to the IgG2a isotype with a kappa light chain and their reactivity recognized against the 41 kDa coat protein of NNV by Western blot analysis. The affinity constants of the six MAbs were measured by enzyme-linked immunosorbent assay (ELISA). All six MAbs reacted with two NNV isolates (SgNag05 and Gemunodo06), while no reactivity was observed with five know fish viruses, namely marine birnavirus, infectious pancreatic necrosis virus, viral hemorrhagic septicemia virus, hirame rhabdovirus, and infectious hematopoietic necrosis virus. Moreover, high ELISA optical density (OD) values (0.87-1.42) were observed in the brain tissues of NNV-infected sevenband grouper, while low OD values (less than 0.12) were recorded in the brain tissues of uninfected fish. These results suggest that these six MAbs are highly competent and useful for the detection of NNV with the RGNNV genotype.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.474-482
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• 2019

Disease monitoring in wild aquatic animals is necessary to obtain information about disease occurrence, disease agents, and the transmission of diseases between wild and cultured species. In this study, we monitored viral diseases in wild marine fish and crustacea caught by trawl in Korea in April and October 2018. We monitored the viral diseases in 977 fish from 39 different species and 287 crustacea from 14 different species. In fish, we collected kidney and spleen to detect viral hemorrhagic septicemia virus (VHSV), red sea bream iridovirus (RSIV), marine birnavirus (MABV), hirame rhabdovirus (HRV), and lymphocystis disease virus (LCDV). In crustacea, we monitored white spot syndrome virus (WSSV), infectious hypodermal and hematopoietic necrosis virus (IHHNV), taura syndrome virus (TSV), infectious myonecrosis virus (IMNV), yellowhead disease virus (YHDV), and white tail disease virus (WTDV) using pleopods, pereiopods, gills, muscle, and hepatopancreases. Although none of the viral diseases tested in this study were detected in the samples, these results will help disease control between aquaculture species and wild aquatic animals.

• Journal of fish pathology
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• v.32 no.2
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• pp.59-67
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• 2019

We developed and subsequently characterized mouse antibodies (MAbs) against viral hemorrhagic septicemia virus (VHSV, genotype IVa), the causative agent of VHS. Five hybridoma clones secreting MAbs against VHSV were established. The MAbs recognized the glycoprotein (MAbs 2C10, 18H4, 23H6, and 30B7) and nucleocapsid protein (15E10) of VHSV by western blot analysis. All five MAbs reacted with VHSV-infected cells and tissue homogenates of VHSV-infected olive flounder (Paralichthys olivaceus) by western blot analysis. Whereas, no reactivity was observed in normal cells and tissue homogenates of normal olive flounder. Moreover, these MAbs reacted with VHSV, but did not react with other fish viruses (infectious hematopoietic necrosis virus, hirame rhabdovirus, spring viraemia of carp virus, infectious pancreatic necrosis virus, marine birnavirus, and nervous necrosis virus) by enzyme linked immunosorbent assay (ELISA). These results indicate that the MAbs are specific to VHSV and can be of value in VHSV detection.

• Korean Journal of Ichthyology
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• v.29 no.1
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• pp.62-68
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• 2017

The Alaska pollock (Gadus chalcogrammus) belongs to the family Gadidae; it is a cold water fish, and has been developed as a novel aquaculture species in Korea. In this study, we describe ongoing surveillance for aquatic animal pathogens based on growth stages. We investigated bacterial flora in rearing water, and monitored pathogens; we also analyzed histopathological traits of abnormal fish. In rearing water, the total bacterial counts were $2.1{\times}10^3cfu/mL$ and Vibrio spp. (52%) were predominant in the larvae stage. In the juvenile and adult stages, the total bacterial counts were $3.4{\times}10^3$ and $3.2{\times}10^2cfu/mL$, respectively (with Pseudomonas sp. as the predominant species; 90% and 52%). This result revealed that the bacterial flora in rearing water changed depending on the feeding types. No virulent-bacteria or problematic viruses (VHSV, viral hemorrhagic septicemia virus; NNV, nervous necrosis virus; MBV, marine birnavirus) were detected from outwardly healthy fish using either culture or PCR assay. Some juveniles (less than 5%) had gas bubbles on the gill lamellae, degeneration of the corneal epithelium, and choroid gland degeneration, suggesting that these symptoms were caused by external injury and secondary infection by opportunistic bacteria. Disease management is important to cope with disease emergence in the novel aquaculture species Alaska pollock.