• Journal of fish pathology
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• v.19 no.3
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• pp.207-214
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• 2006

Diagnostic monitoring in fish farms with land-based tanks and net cases was conducted in eastern, western, southern and Jeju island of Korea for the summer period from 2000 to 2006. Total 3,518-fish samples of marine and freshwater fishes in 25 fish species were tested for pathogens. Fish species tested were olive flounder (Paralichthys olivaceus), fleshy prawn (Fenneropenaeus chinensis Osbeck), black rockfish (Sebastes schlegeli), rock bream (Oplegnathus fasciatus), red sea bream (Pagrus major), black seabream (Acanthopagrus schlegeli), sea bass (Lateolabrax japinicus), gray mullet (Mugil cephalus), rainbow trout (Onchorhynchus mykiss) and others. The infection rates by bacterial pathogens in the years of 2000, 2001, 2002, 2003, 2004, 2005 and 2006 were 22.4%, 34.5%, 14.1%, 15.3%, 17.7%, 13.5% and 5%, respectively. The infection rates by parasitic pathogens were 20%, 33.8%, 12.4%, 14.1%, 9.2%, 10.5% and 10.7%, respectively. The infection rates by viral pathogens were 22.4%, 13.5%, 10.3%, 5.4%, 9.7%, 10.2% and 15.8%, respectively. The infection rates by mixed pathogens were 10.3%, 0%, 44.9%, 50.9%, 31.9%, 38.4% and 39.6%, respectively. The rates of mixed infections were very low until 2001. The rates were higher than those of singer infections from 2002 to 2006. During the diagnostic monitoring from 2000 to 2006, the main bacterial pathogens were Vibrio (41.2%) and Streptococcus (28.8%). The infection rate by protozoa (85.7%) mainly including Scuticociliates and Trichodina was highest. The infection rate by viral necrosis virus (VNNV, 42.2%) was the highest of the viral pathogens.

• Journal of fish pathology
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• v.11 no.2
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• pp.97-104
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• 1998

Since 1989, mass mortality has repeatly occurred in cage-cultured sevenband grouper, Epinephelus septemfasciatus along the southern coast of Korea in the summer season and usually reached over 80% within a few months. Diseased fish showed the clinical signs of anorexia, dark coloration, loss of eqilibrium, spinal swimming behaviour, vertebral deformity and inflation of swim bladder. Histopathologically, necrosis and/or vacuolation of the nerve cells in the brain and retina were observed. We previously reported that the causative agent was filtrable. The causative agent was not culturable in various fish cells; RTG-2, CHSE-214, BF-2, EPC and FHM. However, electron microscopic observation revealed unenveloped icosahedral viral particles with about 30 nm in diameter in the cytoplasm of nerve cells of the brain. The characteristics of the virus was tested by an artificial infection with the filtrate of the homogenate of diseased fish. The pathogenicity of the virus was retained after treatment with ether or heat ($50^{\circ}C$, 30 min) but partly lost by pH 3 or 11 treatment. These results suggest that the causative agent are similar to the fish nodavirus. In order to compare the causative agent with a fish nodavirus, Striped Jack Nervous Necrosis Virus (SJNNV), a polymerase chain reaction (PCR) was performed with primers specific to SJNNV. As a result, about 430 by PCR products were detected from the brain and the eye of both naturally and artificially infected sevenband grouper. All these results represent that the mass mortality in the cultured sevenband grouper is caused by the infection of a nodavirus similar to SJNNV and this is the first report of a fish nodavirus from the cultured sevenband grouper in Korea.

• Journal of fish pathology
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• v.11 no.1
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• pp.23-27
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• 1998

This research was carried out to know the trend in annual occurrence of bacterial disease. The diseased fish were collected from 147 flounder farms of Cheju Island from January, 1991 to December, 1997. Two types of diseases, that is "simple infection" and "mixed infection", were recognized. The simple infections were Vibriosis, Edwardsiellosis Streptococcal infection and Columnaris disease. The mixed infections were caused by a pair of pathogens mentioned above. During the whole period of this study, the highest number of annual occurrence of simple infection was 243 (26.8% of the total) in 1997 and the lowest one was 82 (9.1 %) in 1991. Monthly occurrence of simple infection was the highest number at 132 (14.6% of the total) in August and the lowest one was at 38 (4.2%) in January. Monthly occurrence of the mixed infected disease showed common pattern except November and December. The highest number of annual occurrence of the simple infected disease was 437 (48.2% of the total) in Vibriosis and the lowest one was 22 (2.4%) in Columnaris disease. The highest number of annual occurrence of the simple infected disease was 178 (53.1% of the total) in Vibriosis+Columnaris disease and the lowest one was 28 (8.4%) in Edwardsiellosis+Streptococcal infection.

• Parasites, Hosts and Diseases
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• v.56 no.5
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• pp.501-507
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• 2018

We described here the morphological characteristics for the species identification and fish hosts of Isoparorchis sp. (Digenea: Isoparorchiidae) in the Republic of Korea (Korea). Total 1,371 freshwater fishes collected in Yangcheon (Stream) in Sancheong-gun, Gyeongsangnam-do were examined by the artificial digestion methods to survey the infection status of digenetic trematode metacercariae for 4 years (2013-2016). Adult and larval worms of Isoparorchis sp. were detected in 38 (8.4%) out of 451 fish in 4 species, i.e., Pungtungia herzi, Acheilognathus koreensis, Squalidus japonicus coreanus and Odontobutis platycephala, examined. The infection density was 1.1 worm per fish infected. They were mainly found in the subcutaneous tissues and abdominal cavities. Nodules with worms in the subcutaneous tissues were revealed as the blue ink-colored bulges. Adults leaf-like, $21.6{\times}9.84mm$ in average size. The ratio of body length to body width was 2.20: 1. Oral sucker subterminal, $1.03{\times}1.22mm$. Pharynx muscular, $0.55{\times}0.54mm$. Esophagus very short. Ceca convoluted, terminated near the posterior end. Ventral sucker anterior 1/3.75, $1.99{\times}2.10mm$. The ratio of ventral sucker to oral sucker was 1.74: 1. Testes round to elliptical, both sides of ventral sucker, $1.43{\times}1.33mm$. Vitellaria highly dendritic, posterior 1/3 level. Eggs operculated, embryonated, $52{\times}32{\mu}m$ in size. By the present study, 4 fish species aforementioned are to be listed as the fish hosts of Isoparorchis sp. in Korea and additionally the morphological characteristics are to be described for the species identification.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.3
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• pp.323-329
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• 2016

The effects of dietary antioxidant [saltwort (SW), leek (LK), and dandelion (DD)] supplementation on the growth, body composition, serum chemistry, and challenge test results of juvenile rockfish, Sebastes schlegelii, were determined. In an experiment, 320 fish were randomly distributed into eight, 50-L flow-through tanks (40 fish per tank). Four experimental diets were prepared: the control diet (Con) with synthetic antioxidant: and diets with SW, LK, or DD from natural sources. Each diet was randomly assigned to duplicate tanks of fish, which were hand-fed to satiation twice daily for 8 weeks. After the 8-week feeding trial, 20 fish from each tank were artificially infected with Streptococcus iniae and monitored for 6 days. The dietary additives did not affect survival, weight gain, specific growth rate, feed efficiency (FE), protein efficiency ratio (PER), or plasma chemistry. However, the cumulative mortality of fish fed the SW, LK and DD diets was lower than that of fish fed the control diet beginning 4 days after infection. In conclusion, dietary supplementation with SW, LK, and DD did not affect the growth, FE, PER, or plasma chemistry of rockfish. However, dietary inclusion of SW, LK, and DD lowered the mortality of rockfish following infection with S. iniae.

• Journal of fish pathology
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• v.6 no.2
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• pp.205-218
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• 1993

On the development of hirame(Paratichtys olivaceus) culture, outbreak of scuticociliata infection was reported to cause severe damage in Japan. To establish effective measures for isolation and cultivation of this ciliate, we tried to culture this pathogenic ciliate using medium for bacteria and fish cell lines in vitro. Scuticociliata from the brain tissues of infected fish was aseptically inoculated to CHSE-214 cells cultured in MEM-10 without antibiotic. Scuticociliata grew well and the number of ciliate reached $10^6\;cells/ml$ at temperatures of $15^{\circ}C$ to $20^{\circ}C$ for 10d. The number of ciliate cultured in the cell lines is 10 times higher than the numbers cultured in the liquid medium alone. This ciliata could be cloned by dilution method. Scuticociliata isolated could grow well on 42 different cell lines that were established from marine fish, warm freshwater fish, and salmonids. This ciliate could be preserved in liquid nitrogen for more than 6 months. Subsequently, we observed the optimal temperature and salinity for growth, and tested the sensitivities of this organism to formaldehyde, flagyl(Metronidazole), Ekuteshin(Combination compound of sulfamonometoxin and ormethoprim), and ozonixation. Optimal temperature for growth was $25^{\circ}C$ and salinity was 1.0 to 1.5%. Washed scuticociliata was killed by formaldehyde at the concentration of 50ppm for 10min, but was not completely killed even at a high concentration of 400ppm for 20min in MEM-5. Flagyl and Ekuteshin can inhibit the growth of scuticociliata at the concentration of 1,000 and $100{\mu}g/ml$ in MEM-10, respectively. More than 99% of this scuticociliata could be killed by ozonization at a dose equivalent to $1.0mg/\ell$ oxidant for 30sec in sea water. Isolated scuticociliata showed the pathogenicity to the cultured hirame by artificial infection(I. P. injection, $10^5\;cells$/fish). The number of scuticociliata in the water could be counted by most probable number(MPN) method using tissue culture, and the minimum detectable number was $1.8\;cells/\ell$. The number in the reservoir tank for water supply to the culture tank was 110 cells/l. After cleaning by elimination of the sediments from of the reservoir tank and disinfected with formaldehyde, number of scuticociliata decreased and was counted less than $1.8\;cells/\ell$ and infection rate of cultured hirame was decreased.

• Journal of fish pathology
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• v.24 no.2
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• pp.161-166
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• 2011

The metacercariae of Clinostomum complanatum (Rudolphi, 1814) were isolated in the whole body muscle of wild freshwater fish, spotted barbel gudgeon (Squalidus multimaculatus Rosoya et Jeon) from the local river in Yeongdeok, Gyeongsangbuk-do, Korea. The infected fish with bumpy body surface by "yellow grub" showed erratic swimming behavior and some fish were died. The isolated excysted metacercariae were tongue shaped and 2.85~5.89 mm ${\times}$ 0.8~1.99 mm in size. 1~98 metacercariae were isolated in individual fish and mean infection intensity was 25. All examined adult spotted barbel gudgeon sizing 7 cm in body length were infected. This is the first report of disease outbreak and mortality caused by C. complanatum infection in wild freshwater fish in Korea.

• Parasites, Hosts and Diseases
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• v.35 no.3
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• pp.165-170
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• 1997

The present study was performed to analyze the infection status of trematode metacercariae in fishes caught from Chunamchosuchi (pond) located in Uichang-gun. Kyongsangnam-do. A total of 130 freshwater fish of 5 species was collected by a fish net and fish traps from November, 1995 to May, 1996. They were examined under a stereomicroscope after artificial digestion with pepsin-HCI solution. A total of 8 species or metacercaria, i. e. Clonorchis sinensis, Echinochnsnw japonicas, Cvathocotwle orientalis, Diplostomun sp.. Metorchis orientalis. Holostephcnw nipponicw, Exorchis oviformis and unidentified echinostome, was detected from them. The metacercariae of C. sinenesis were found in 8/20 (40.0%) Accnthorhodeus Qsmwsi, 20/20 (100%) Cutter breuiccudc, 31/45 (68.9) Cultriculus eigenmanni and 21/25 (84.0%) Pseunorasborc pronga, and the average number of metacercariae detected in each fish species were 1.9, 31.7. I5.3, and 73.0. From the above results, it was confirmed that fresh-water fishes from Chunamchosuchi (pond) were highly infected with metacercariae of avian trematode, i.e. C. orientolis, H. nipponicus. M. oui,entnlis, E. jcponicw and Diplostonum sp., and 4 species of fish. P. parvc, C. breuiccudn, C. eigenmnnni and A. asmussi, were infected with metacaecariae of C. sinensis.

• Journal of fish pathology
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• v.36 no.2
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• pp.311-321
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• 2023

The efficacy of the alginate microsphere (Alginate MS) oral vaccine against Miamiensis avidus in olive flounder (Paralichthys olivaceus) was confirmed through challenge infections by both immersion and injection routes. In trial 1, the formalin-inactivated M. avidus coated with alginate, designated as 'IMa+Alginate MS' group, and the IMa group were administered with vaccines mixed with feed, with a total antigen dose of 3.75 × 10⁶ cells/fish. When challenged with immersion infection at five weeks post vaccination, the relative percent survival (RPS) in the IMa+Alginate MS group was 50% (immersed in 50% seawater) and 37.5% (immersed in 100% seawater). The group that received only IMa showed a low survival rate. In trial 2, the antigen was fed mixed with feed at a total dose of 2.38 × 10⁶ cells/fish for 5 days. Two weeks after oral vaccination, fish were intraperitoneally injected for infection. The RPS in the IMa+Alginate MS group was 30.8%, while the IMa-only group showed no vaccine efficacy. At five weeks post vaccination, when subjected to challenge infection by immersion in 50% seawater, the IMa+Alginate MS group recorded a RPS of 42.9%, whereas the IMa group had a RPS of 14.3%. The results of this study indicate that coating M. avidus antigen with alginate can provide higher protection in olive flounder compared to administering the antigen alone.

• Journal of fish pathology
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• v.1 no.1
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• pp.51-57
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• 1988

Pleistophora disease is well known as microsporidiosis at eel cultural farms in Korea in recent years. Major objects of this study were to undertake the induction of Pleistophora infection experimentally and to carry out histopathological investigation from December 1984 to June 1986. Experimental infection of Pleistophora spores into young eels was carried out by oral and immersed administration. Both methods induced the same symptom successfully as that in naturally occurring diseased fish. Remarkable whitish lesions developed mainly on the body surface around the abdomen when orally administrated. On the other hand, they were scattered over the whole body when administrated through immersion. Histopathological investigation revealed that some cysts in the muscle were observed 21 days after administration. Spores were developed within the cyst. Each sporont has undergone several nuclear divisions to form a pair of multinucleate cells (Sporoblasts) enclosed within a common coat (Pansporoblast). All stages were surrounded by cyst. The cysts were destroyed and mature spores were scattered in the muscle.