• Parasites, Hosts and Diseases
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• v.59 no.1
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• pp.89-95
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• 2021

Microcotyle sebastis is a gill monogenean ectoparasite that causes serious problems in the mariculture of the Korean rockfish, Sebastes schlegelii. In this study, we isolated the parasite from fish farms along the coasts of Tongyeong, South Korea in 2016, and characterized its infection, morphology and molecular phylogeny. The prevalence of M. sebastis infection during the study period ranged from 46.7% to 96.7%, and the mean intensity was 2.3 to 31.4 ind./fish, indicating that the fish was constantly exposed to parasitic infections throughout the year. Morphological observations under light and scanning electron microscopes of the M. sebastis isolates in this study showed the typical characteristics of the anterior prohaptor and posterior opisthaptor of monogenean parasites. In phylogenetic trees reconstructed using the nuclear 28S ribosomal RNA gene and the mitochondrial cytochrome c oxidase I gene (cox1), they consistently clustered together with their congeneric species, and showed the closest phylogenetic relationships to M. caudata and M. kasago in the cox1 tree.

• Parasites, Hosts and Diseases
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• v.58 no.3
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• pp.333-338
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• 2020

A small survey was performed to investigate the recent infection status of Clonorchis sinensis and other zoonotic trematode metacercariae in freshwater fish from a local market of Yen Bai city, Yen Bai province, northern Vietnam. A total of 118 fish in 7 species were examined by the artificial digestion method on March 2016. The metacercariae of 4 species of zoonotic trematodes, i.e., C. sinensis, Haplorchis pumilio, Haplorchis taichui, and Centrocestus formosanus, were detected. The metacercariae of C. sinensis were found in 62 (69.7%) out of 89 fish (5 species), and their intensity of infection was very high, 81.2 per fish infected. Prevalences of 3 intestinal flukes, H. pumilio, H. taichui and C. formosanus, were 75.0%, 47.6%, and 31.7% in positive fish species, respectively, with the metacercarial intensities of 15.5, 10.3, and 2.2 per fish infected. From the above results, it has been confirmed that various species of freshwater fish continue to play the role of the infection source of C. sinensis and other zoonotic trematodes in Yen Bai city, Yen Bai province, northern Vietnam. It is of particular note that the prevalence and intensity of C. sinensis metacercariae are much higher than those reported in previous studies in fish in northern Vietnam.

• Parasites, Hosts and Diseases
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• v.46 no.4
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• pp.247-251
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• 2008

This study investigated freshwater fish for their current infection status with metacercariae of Clonorchis sinensis in Korea. Twenty-one species of freshwater fish (n = 677) were collected from 34 regions nationwidely from February 2007 to June 2008. They were individually examined by digestion technique. Eight species of freshwater fish from 17 different regions were recognized positive for the metacercariae of C. sinensis. The positive rates (range of metacercariae number per fish) of fish by the species were as follows: 48% (1-1,142) in Pseudorasbora parva, 60% (1-412) in Pungtungia herzi, 15.7% (1-23) in Pseudogobio esocinus, 29% (1-7) in Acheilognathus intermedia, 21% (1-4) in Odontobutis interrupta, 33% (1-6) in Zacco temmincki, 3.6% (1-4) in Zacco platypus, and 26.3% (1) in Hemibarbus labeo. The two species, P. parva and P. herzi, are able to be the index fish for estimation of C. sinensis transmission in a certain locality. Still several species of freshwater fish are briskly transmitting C. sinensis infection in many riverside areas of southern Korea.

• Korean Journal of Ichthyology
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• v.28 no.3
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• pp.141-146
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• 2016

Experimental infection of rainbow trout Oncorhynchus mykiss with viral hemorrhagic septicemia virus (VHSV, genotype IVa) from olive flounder Paralichtys olivaceus was examined. The cumulative mortalities of three different lot of rainbow trout fry challenged with VHSV ($10^{6.3-7.3}TCID_{50}$/fish) were less than 15%. No difference of virulence was observed in experimental infection using 5 in vivo passaged VHSV and original VHSV. No mortality was observed in seawater-reared rainbow trout (adult) challenged with VHSV ($10^{5.3-6.3}TCID_{50}$/fish) and virus was not detected in the fish. We thus concluded that VHSV from olive flounder has low virulence to rainbow trout fry, but not pathogenic to seawater-rainbow trout (adult).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.628-636
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• 2020

Streptococcosis in the olive flounder Paralichthys olivaceus can be caused by Streptococcus parauberis. We compared three routes of administration for experimental injections of the S. parauberis 19FBSPa0003 strain in the olive flounder. Pathological changes were observed during the experimental infection. Inflammation of the serous membrane in the liver, intestine, spleen and heart was the major pathological change found in the infected olive flounder. No mortality was observed in fish that received intraperitoneal (IP) injection at less than 1×10⁴ colony-forming unit (CFU)/fish. The lethal dose 50 for olive flounder, given an intravenous (IV) injection, was 7.94×10⁴ CFU/fish. Fish with a higher concentration of IV injected S. parauberis (1×10⁸ CFU/fish) died within a maximum of two days. However, serious necrosis and bacterial proliferation in ellipsoidal cells of the spleen and heart tissues were found in moribund or dead fish, 1-2 days after IV injection. Similar histopathological signs were observed in olive flounder inoculated by subcutaneous (SC) infected and naturally infected. In addition, SC was also strongly associated with bacteria concentration and cumulative mortality rate. Based on these results, SC is the recommended method for artificial infection by S. parauberis in the olive flounder.

• Journal of Microbiology and Biotechnology
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• v.33 no.11
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• pp.1412-1419
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• 2023

Retroviral integration into ancient vertebrate genomes left traces that can shed light on the early history of viruses. In this study, we explored the early evolution of retroviruses by isolating nine Spuma endogenous retroviruses (ERVs) and one Epsilon ERV from the genomes of Agnatha and Chondrichthyes. Phylogenetic analysis of protein sequences revealed a striking pattern of co-evolution between jawless fish ERV and their host, while shark ERV underwent ancient cross-class viral transmission with jawless fish, ray-finned fish, and amphibians. Nucleotide sequence analysis showed that jawless fish ERV emerged in the Palaeozoic period, relatively later than ray-finned fish ERV. Moreover, codon analysis suggested that the jawless fish ERV employed an infection strategy that mimics the host codon. The genealogical diversity of ERVs in the jawless fish genome highlights the importance of studying different viral species. Overall, our findings provide valuable insights into the evolution of retroviruses and their interactions with their hosts.

• Journal of fish pathology
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• v.5 no.1
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• pp.1-7
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• 1992

CHSE(Chinook Salmon Embryo)-214 fish cell lines was cultured in Eagle's minimal medium (MEM) supplemented with 10% fetal bovine serum and 2mM-glutamin. Optimum growth temperature of CHSE-214 cell line was $20^{\circ}C$. Infectious pancreatic necrosis virus(IPNV) was successfuly multiplied and showed the cytopathic effect in CHSE-214 cell line. Infection symptom of IPNV was observed with inverted phase contrast microscopy. At 6h-12hrs post-infection, the cells infected with IPNV were similer to normal cells. At 18-24hrs post-infection, the cells were somewhat round form and a little swollen form than normal cells. At 30hs post-infection, the cells were becoming more abnormal cells. At 48-68 post-infection, the infected cells were lysed and showed the severe cytopathic effect.

• Journal of Microbiology and Biotechnology
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• v.29 no.8
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• pp.1324-1334
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• 2019

Fish mycobacteriosis is a common bacterial disease in many species of freshwater and marine fish and has caused severe loss of fish production. Mycobacterium marinum has been the most prevalent pathogen observed in several outbreaks of mycobacteriosis of farmed sturgeons in China. However, the immune responses and pathology of sturgeons in mycobacterial infection are rarely studied. Therefore, we used the Illumina RNA-seq method to analyze the transcriptome profile of Acipenser schrenckii challenged with Mycobacterium marinum. To begin, 168,220 non-redundant contigs were acquired from the infection and control groups, and among these, 33,225 contigs have acquired annotations. A total of 4,043 differently expressed (DE) contigs between the two groups were identified, and among these, 2479 were up-regulated and 1564 were down-regulated in the infected fish. A total of 1,340 DE contigs with acquired annotations in KEGG were enriched for 124 pathways including the TNF signaling pathway, and the Toll-like receptor signaling pathway. The roles of DE genes involved in significant pathways and other processes were discussed. The 2,209 DE contigs that have yet to acquire proper annotation may represent candidate genes associated with infection in sturgeons and are expected to serve as immunogenetic resources for further study. To our best knowledge, this is the first transcriptome study on sturgeons under bacterial infection.

• Journal of fish pathology
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• v.3 no.2
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• pp.51-60
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• 1990

Parasites of freshwater fishes in Cheju-do were studied from May 1989 to April 1990, and incidence of infection in 16 fish species was reported. Protozoan parasites (Trichodina sp., Chilodonella sp., Ichthyophthirius sp., Vorticella sp., Myxidium sp., Myxobolus sp., Henneguya sp:, Ichthyobodo sp., and Trychophrya sp.), water mold (Saproregnia sp.), two monogenes (Dactylogyrus sp. and Gyrodactylogyrus sp.), Trematods, Cestods, Nematods, Acanthocephalas, parasitic copepods(Lernaea sp. and Pseudergasilus sp.) and a Hirudinea were recognized as freshwater fish parasites in Cheju-do. Trichodina sp. showed the highest infection rate (18.3%). Fifty seven individual fishes out of 311 were infected by this parasite. Nematods showed the second highest infection rate (13.5%). Dactylogyrus sp., Acanthocephalas, and Trematods showed the third (4.8%), fourth (4.2%), and fifth (2.6%) infection rate respectively. Of the 16 fish species Cryptocentrus filifer (Gobiidae) showed the highest infection rate. Nineteen fish out of 28 have Trichodina sp., and 14 fish out of 28 have Nematods. Those infection rates were 67.9% and 50.0% respectively. No parasites were collected from the fishes of Gwangryung vally, Dosoon-chun, Gangjeong-chun, and Hyodon-chun.

• Parasites, Hosts and Diseases
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• v.27 no.1
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• pp.41-46
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• 1989

This study was performed to observe the infection rate and infection intensity of fresh water fish such as pale chub (Z. platypus) and dark chub (Z. temminckii) with the metacercariae of C. armatus. The fish were caught in several rivers and streams from June to September, 1988 and examined by artificial digestion technique. Total 370 fish were caught at 19 rivers. The metacercarial (C. armatus) infection rate and average burden in Z. Platypus were 86.8% and 224, and those in Z. tsmminckii were 78.5% and 131. The infection rate and burden per fish were 73.4% and 32 in the fish caught from the Han river, and 88.0% and 44 from the Youngsan river. All fish caught from the Keum and the Tamjin river were infected and their mean metacercarial density was 45 and 59 respectively. The infection rate and density in fish caught from the Seomjin and Nagdong rivers were 100% and 119, and 81.0% and 348 respectively. From this study, it is confirmed that C. armatus is widely distributed along 5 major rivers in Korea.