• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.1021-1028
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• 2012

In this study, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the rapid, sensitive, and inexpensive detection of nervous necrosis virus (NNV) in olive flounder, Paralichthys olivaceus, in Korea. A set of six specific primers was designed to target the RNA 2 gene encoding the coat protein of Korean NNV strains. The RT-LAMP reaction successfully detected NNV after 30 min at $65^{\circ}C$. When the sensitivities among RT-LAMP, RT-PCR, and nested RTPCR were compared, the RT-LAMP was shown to be able to detect the RNA template at $2.58{\times}10^{-2}\;TCID_{50}/ml$, whereas the RT-PCR and nested RT-PCR were only able to detect the RNA template at $2.58{\times}10^2\;TCID_{50}/ml$ and $2.58TCID_{50}/ml$, respectively. Thus, the sensitivity of the RT-LAMP assay was higher than those of the RT-PCR assays. In the specificity test of the RT-LAMP, 2 genotypes of NNVs (SJNNV and RGNNV) were positive; however, no other fish viruses were positive with the primers, indicating that the RT-LAMP assay is only specific to NNV. A total of 102 olive flounder were collected from hatcheries between 2009 and 2011. The occurrence of NNV in olive flounder was determined to be 53.9% (55/102) by the RT-LAMP. On the other hand, the prevalence based on the nested RT-PCR and RT-PCR results was 33.8% (34/102) and 20.6% (21/102), respectively. This result indicates that the RT-LAMP assay developed in this study is suitable for early field diagnosis of NNV with high sensitivity.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1157-1170
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• 2023

Ascites is a condition in which body fluids are abnormally accumulated in the fish's abdominal cavity, and is an important indicator of the health of flounder. Ascites can occur in the process of infection with bacteria, viruses, parasites, etc., which causes abdominal distension, sluggish growth, and weight loss. In this paper, we tried to find the correlation with other symptoms or diseases that affect ascites symptoms in flounder. As experimental data, ascites symptoms were divided into three states: no ascites, ascites transparent, and ascites opaque, and disease diagnosis data of cultured flounder collected for 7 years were used. After performing an appropriate preprocessing process for the random forest machine learning method, other symptoms and disease factors related to ascites were extracted, and it was confirmed that the proposed model could present the main factors related to ascites.

• Journal of fish pathology
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• v.27 no.2
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• pp.91-97
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• 2014

Since the "Aquatic life disease control act" was established in 2009, we have monitored OIE notifiable and legally designated diseases which are associated with white shrimp Litopenaeus vannamei but are as yet outbreak in South Korea. We had monitored only two viral diseases of YHD and IMN, but further added IHHN, TS and WTD in an attempt to reinforce monitoring as a countermeasure against the increasing possibility of imported diseases led by continuous growth in global fisheries trade. We also increased the number of monitoring areas, and shrimp farms. In 2013, we examined a total of 2,650 white shrimp from 29 hatcheries and farms to check whether they were infected with any of the 5 diseases (YHD, IMN, IHHN, TS, WTD). The result showed that none of the samples contained the viruses. To regulation of the exotic diseases from landing in our country and to strengthen prevention, management and control of the diseases on a national level, we must continue the surveillance monitoring of the diseases.

• Journal of fish pathology
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• v.35 no.1
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• pp.27-40
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• 2022

Yellow head virus (YHV), Infectious hypodermal and hematopoietic necrosis (IHHNV), Taura syndrome virus (TSV), and Infectious myositis virus (IMNV) cause serious mortality to Penaeidae shrimp in the aquaculture. In this study, YHV, IHHNV, TSV, and IMNV were surveyed from imported frozen shrimps between 2019 and 2020 via molecular diagnostic assay. Among 10 shrimp groups, YHV (n=1) and IHHNV (n=4) were detected by RT-PCR and PCR, respectively. From the phylogenetic analysis based on the partial ORF 1b region of YHV, YHV was classified into YHV genotype 3 (YHV3). And IHHNVs (n=2) detected from Litopenaeus vannamei belong to infectious IHHNV type 2. Although IHHNVs (n=2) identified from Penaeus monodon showed PCR positive results (MG 831F/R primer set), the sequences of ORF 2 and 3 were not amplified, suggesting that those samples might possess type A IHHNV related sequence of P. monodon. Furthermore, in the challenge test, even though PCR-detected isolates (YHV3/type A IHHNV related sequence or infectious IHHNV type 2) were not induced mortality to L. vannamei, viral genes were amplified suggesting that the viruses in the frozen shrimp could be non-pathogenic particles which are not enough to induce mortality.

• Journal of fish pathology
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• v.24 no.2
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• pp.65-73
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• 2011

In analysis of DNA viruses from the contaminated shellfish using PCR, preparation method of template DNA is an important factor to get enough copy number of viruses. In this study, we evaluated the efficiency of PCR template of Megalocytivirus (sT50mg-D) DNA obtained from 50 mg digestive gland homogenate of oyster using commercial method, and compared with that obtained from 5 g of the same tissues (T5g-D) after PEG precipitation procedures of virus. Both templates DNA suspended in the same volume of distilled water showed positive results by primary PCR with 35 cycles, and the presence of Megalocytivirus was confirmed in oysters collected from cultured farms in Korea. Moreover, PCR with sT50mg-D allowed us to discriminate the contaminated oyster individually, that can not be done in PCR with T5g-D prepared from the mixture of three different individual oyster to get 5 g digestive gland homogenate. In quantitative analysis with real time PCR, Megalocytivirus concentrations in 50 ${\mu}l$ templates prepared using 0.5~50 mg of one positive sample were appeared in the range 6.14E+00~1.2E+02/${\mu}l$. We were not able to get positive result using template DNA contained less than 6.14E+00 copies. Consequently, 2-step PCR performed with DNA extracts from oyster homogenate of small amount (sT50mg-D) i) was enough to detect the contaminated Megalocytivirus in shellfish, ii) allowed us to do the analysis for individual shellfish rather than mixture of several shellfish and iii) showed the presence of Megalocytivirus in oyster from Korea.