In this study, carp edemavirus disease and herpesviral hematopoietic necrosis were examined in carp (Cyprinus carpio) and crucian carp (Carassius auratus) imported from China. From August 2016 to May 2017, 100 carp and 300 crucian carp were examined. There were no clinical symptoms in all the tested fish, and no internal or external parasitic infections were identified except for the detection of Argulus sp. in one leather carp. Carp edema virus disease was examined by PCR in C. carpio, but all were negative. In C. auratus, herpesviral hematopoietic necrosis was tested by PCR and 4 out of 300 were positive. The results of this study are expected to be useful as basic data for conducting risk analysis on the relevant organisms and counterpart countries or for designating new pathogens for quarantine.

실험실에서 순환여과시스템으로 5-6개월 사육하던 넙치 치어에서 아가미의 심한 빈혈을 나타내는 질병이 발생하였다. 현미경관찰에서 아가미에서는 유충이, 입천정에서는 성숙한 성충이 관찰되었다. 성충의 체장은 5.60-9.32 mm이며 방추형 몸의 길이는 3.83-6.32 mm, 부착기는 방추형 몸에서 부터 연결된 isthmus의 끝부분에 꽃자루 모양으로 존재하였고 부착기의 끝에는 8개의 파악기가 있었다. 충의 형태학적 관찰로부터 단생류에 속하는 Neoheterobothirum hirame로 동정하였다. 감염어의 적혈구용적는 평균 10.3±2.8%로 정상 넙치의 31.4±4.2%보다 현저히 낮았다. 병리조직학적으로 N. hirame에 감염 된 넙치는 아가미 새판과 새엽을 흐르는 혈관내의 적혈구가 감소하고 비장의 적수(red pulp) 영역이 감소되고 간세포는 위축이 관찰되었다. 이상의 결과로부터 넙치에 심한 빈혈을 일으킨 원인은 N. hirame인 것을 밝혔다. 이 연구는 순환여과식 사육시스템에서는 사육수의 교환이 적으므로 소독장치가 충분하지 못할 경우 병원체의 증식이 문제가 될 수 있는 예를 보이고 있다.

We found skin flukes in snubnose pompano (Trachinotus blochii) from a public aquarium and attempted clear identification of them to the species level by morphology and molecular analyses. Skin flukes were collected from snubnose pompano showing dyspnea, anorexia and mild hemorrhage on the skin. All the fish samples (n=2) were infected with the flukes on the skin, gill and eyes, covered with excessive mucus. The isolated worms were transferred for making slide specimen and PCR amplification targeting 18S rDNA, 28S rDNA, mitochondrial cytochrome c oxidase subunit 1 (mt cox1) and cytochrome b (Cytb) genes for further analyses. Morphology and measurements data of our slide specimen coincided with those of Neobenedenia girellae. The sequence data of 2 genes (28S rDNA and Cytb) and the phylogenetic trees revealed that our specimen consistently belonged to the N. girellae clade. For 18S rDNA and mt cox1 genes, there was no sequence of either of these 2 Neobenedenia species from the type host available in GenBank. This is the first record of N. girellae in snubnose pompano, but it is still unclear if the snubnose pompano is a natural host for N. girellae or not because N. girellae is known to have an unusual broad host range and the host-switching can occur particularly in captive conditions such as aquarium or aquaculture facilities.

In recent years, global warming is causing dramatic environmental changes and deterioration, such as hypoxia, leading to reduced survival rate and growth performance of farmed aquatic animals. Hence, understanding systemic immuno-physiological changes in fish under environmental stress might be important to maximize aquaculture production. In this study, we investigated physiological changes in rainbow trout exposed to hypoxic stress by monitoring changes in blood chemistry, leukocyte population, and expression levels of related cytokine genes. Hematological and serological factors were evaluated in blood obtained from rainbow trout sampled at a dissolved level of 4.6 mg O₂ L^-1 and 2.1 mg O₂ L^-1. Blood and head kidney tissue obtained at each sampling time point were used to determine erythrocyte size, leukocyte population, and cytokine gene expression. The level of LDH and GPT in fish under progressive hypoxia were significantly increased in plasma. Likewise, the (Granulocyte + Macrophage)/lymphocyte ratio (%) of fish exposed to hypoxia was significantly lower than that in fish in the control group. Such changes might be due to the rapid movement of lymphocytes in fish exposed to acute hypoxia. In this study, significant up-regulation in expression levels of IL-1β and IL-6 gene appeared to be involved in the redistribution of leukocytes in rainbow trout. This is the first study to demonstrate the involvement of cytokines in leukocyte trafficking in fish exposed to hypoxia. It will help us understand systemic physiological changes and mechanisms involved in teleost under hypoxic stress.

Hypoxia is a serious problem in the marine ecosystem causing a decline in aquatic resources. MicroRNAs (miRNAs) regulate the expression of genes through binding to the corresponding sequences of their target mRNAs. Especially, miRNAs in the cytoplasm can be secreted into body fluids, which called circulating miRNAs, and the availability of circulating miRNAs as biomarkers for hypoxia has been demonstrated in mammals. However, there has been no report on the hypoxia-mediated changes in the circulating miRNAs in fish. miR-210 is known as the representative hypoxia-responsive circulating miRNA in mammals. To know whether fish miR-210 also respond to hypoxia, we analyzed the change of circulating miR-210 quantity in the serum of olive flounder (Paralichthys olivaceus) in response to hypoxia. The expression of hypoxia related genes, hypoxia inducible factor 1α (HIF-1α) and the heat shock protein 90α (HSP90α) was also analyzed. Similar to the reports from mammals, miR-210-5p and miR-210-3p were significantly increased in the serum of olive flounder in response to hypoxia, suggesting that circulating miR-210 levels in the serum can be used as a noninvasive prognostic biomarker for fish suffered hypoxia. The target genes of miR-210 were related to various biological processes, which explains the major regulatory role of miR-210 in response to hypoxia. The expression of HIF-1α and HSP90α in the tissues was also up-regulated by hypoxia. Considering the critical role of HIF-1α in miR-210 expression and HSP90 in miRNAs function, the present up-regulation of HIF-1α and HSP90α might be related to the increase of circulatory miR-210, and the interaction mechanism among HIF-1α, HSP90α, and hypoxia-responsive microRNAs in fish should be further studied.

Doxycycline is a semi-synthetic broad-spectrum antibiotic, and it has been used to get rid of bacteria in animals and humans. The use of antibiotics has greatly contributed to the aquaculture production although its misuse sometimes presents public health problems. This study was performed to investigate the toxic effects of doxycycline on whiteleg shrimp (Litopenaeus vannamei) administered for possible infection treatments. The shrimp were allocated into four groups and doxycycline was fed three times a day for 7 days at 0, 20, 50 and 100 mg/kg to each group. After 24 hr following the 7-day treatment, hemolymph and hepatopancreas were used for blood and biochemical analysis: Total hemocyte counts, Total protein, Total cholesterol, Gluscose, Glutamic pyruvic transaminase, Glutamic oxaloacetic transaminase, Glutathione peroxidase, Superoxide dismutase, Glutathione-s-transferases, Total antioxidant capacity colorimetric and Acid phosphatase. In addition, histopathological examination was performed on the hepatopancreas and muscle. It was observed that body weight gain was significantly retarded in 100 mg/kg doxycycline group. Doxycycline was found to induce biochemical or functional disorders at 100 mg/kg as observed many of the blood and biochemical parameters were significantly reduced. In conclusion, it was judged that there will be no major toxicity problems with doxycycline when used for shrimp aquaculture at regular doses.

본 연구에서는 점액포자충에 의한 넙치의 여윔증 치료 후보물질을 탐색하기 위하여, Coxi-stop, Coxiclin 및 BLEAN80 등의 제품을 사용하여 in vitro 및 in vivo 실험을 실시하였다. 톨트라주릴이 주성분인 Coxi-stop의 경우, BF-2 cell을 사용한 in vitro 실험에서 점액포자충의 활성을 감소시키는 결과를 보였고, cell lysis와 같은 세포 독성 현상이 나타나지 않았다. In vivo 실험에서 Coxi-stop을 사용하여 약욕한 실험군은 대조군에 비하여 누적폐사율이 낮게 나타났으며, 이것은 톨트라주릴이 어류 기생충성 질병에 치료 효과가 있다는 기존의 보고와 유사한 결과이다. 본 연구에서는 톨트라주릴이 넙치의 여윔증 치료제로서 가능성이 있는 후보 물질이라는 것을 제시한다.

Fish culture is constantly threatened by various infectious diseases which are largely transmitted by water. Plasma technology is being used to sterilize polluted water in many industries. In this study, two bacterial pathogens Aeromonas salmonicida and Streptococcus iniae, and a virus (viral hemorrhagic septicemia virus, VHSV) were subjected to plasma water that was produced by a corona discharge system. Growth of A. salmonicida was greatly inhibited from 10^5.61 CFU/ml in positive control to 10^3.51 CFU/ml in treated group by only 60 sec contact with plasma water. Similarly, S. iniae was inhibited from 10^5.85 CFU/ml to 10^3.40 CFU/ml. VHSV titer also decreased from 10^4.1 TCID₅₀/ml to 10^1.45 TCID₅₀/ml by the same treatment. Activation of water by the plasma was confirmed by the existence of ozone in the plasma water. These results suggest that plasma water could efficiently disinfect fish pathogens, possibly by the action of reactive oxygen species contained in the plasma water.

A survey was conducted to investigate viral infections in 184 whiteleg shrimp (Litopenaeus vannamei) collected from nine farms and one wholesale fish vendor during 2018 and 2019. Gill and abdominal muscle of shrimp were tested for the presence of five viruses, viz. infectious hypodermal and haematopoietic necrosis virus, taura syndrome virus, infectious myonecrosis virus, yellow head virus genotype 1, and covert mortality nodavirus by reverse transcription-polymerase chain reaction (RT-PCR) and PCR. These viruses were not detected in any of 184 samples, screened under the study.

This study was performed for screening yellow head virus(YHV) complex in 252 including 235 white leg shrimps (Litopenaeus vannamei) and 17 oriental shrimp (Fenneropenaeus chinensis) collected from 18 farms located in southwestern province of Korea. The virus complex was detected by nested reverse-transcriptase polymerase chain reaction (RT-PCR) assay. In the assay, amplicons were resulted in RNAs exracted from 38 shrimps (21 white leg shrimps and 17 oriental shrimps) obtained from 7 farms. In phylogenetic analysis using sequences of ORF1b gene, all 38 sequences obtained in this study formed an independent lineage with YHV-8 genotype firstly isolated in China, belonged to an YHV-8 clade.

In the study, we investigated the effect of Taurine-F^TM, which is a commercially available fishery nutritional supplements complex, on anti-hepatotoxicity stressed with thioacetamide (TAA) and innate immune responses in olive flounder. To investigate the change in liver toxicity, firstly, TAA (30 ppm/100 g of fish) was intraperitoneally (i.p.) administered 12 hr after the intramuscular (i.m.) injection of Taurine-F^TM (0.02 ml/100 g of fish)(Taurine/TAA). Secondly, Taurine-F^TM was i.m. injected 24 hr after the administration of TAA (TAA/Taurine). Finally, TAA was administered simultaneously with Taurine-F^TM (TAA+Taurine). All blood samples were collected 24 hr after injection. GOT level in group Taurine/TAA appeared similar to the control, whereas group TAA/Taurine and TAA+Taurine showed significantly increased (p<0.05) levels compared to the control. In GPT level, group Taurine/TAA and TAA/Taurine showed elevated levels compared to the control, whereas no significant difference was observed between group TAA+Taurine and the control. Serum ACH₅₀ activity was significantly (p<0.05) augmented 24 hr after Taurine-F^TM injection compared to the control group, whereas no significant increase was observed 48 hr after Taurine-F^TM injection. On the other hand, serum lysozyme activity elevated in an acute stressed condition appeared significantly down-regulated 24 and 48 hr after Taurine-F^TM injection compared to the control. In conclusion, i.m. injected Taurine-F^TM augmented flounder serum complement activity and decreased a possible handling stress resulting in reducing a serum lysozyme activity and recovering hepatotoxicity. Thus, it is assumed that i.m. injection of Taurine-F^TM mixed with antibiotics or available vaccines could be utilized as an anti-hepatotoxic recipe in fish culture industry.

Fish bacterial diseases have spread and caused serious problem for cultured marine fish in Korea. The important bacterial disease affecting mariculture such as olive flounder (Paralichthys olivaceus) are caused by Edwardsiella tarda, Vibrio scophthalmi and Streptococcus parauberis. For the bacterial disease protection in aquaculture industry, the water treatment is needed in aquaculture system. During the last decades atmospheric pressure non-thermal plasma in contact with liquids have received a lot of attention of environmental and medical application. In this study, we determined the disinfectant effect in seawater and three major fish bacterial disease pathogens by using low frequency plasma treatment. Three fish bacteria (E. tarda, V. schophthalmi, S. parauberis) were not detected within 16 min, 150 min and 270 min of 20 L, 500 L and 1 ton seawater post low frequency plasma treatment, respectively. Three major fish bacterial disease pathogens were not detected within 2 min after the low frequency plasma treatment, suggesting that the low frequency plasma possess disinfectant effectiveness.

Although aquaculture production rates grown over the years, aquatic animal diseases occur every year which causes substantial economic losses. When an aquatic animal is infected with an aquatic animal pathogen it is either incinerated or buried according to the aquatic life disease control act. Although these methods prevent the spread of disease, it is not environment friendly. Here, we developed an aquatic animal rendering equipment for disposal of fish waste which is environment-friendly and efficient. Also, fertilizer components of fish waste were evaluated value for recycling. The mobile rendering equipment was designed for field operation and/or high temperature and pressure system, oil and water separator, and shredding drying apparatus. During the experiment (July-2016 to November-2016), a total of 53,824 kg fish waste was collected, and 29,216 kg compost of rendering by-product was made. Also, compost made from viral (Viral hemorrhagic septicemia virus) infected fish did not reflect any detectable pathogen. The concentration of nitrogen, phosphorus, and organic matter in the fish waste compost were 2.17%, 26.98%, and 92.44%, respectively. The results suggest that fish waste used in this study was decomposed efficiently as per the official standard for fertilizer product. This equipment can be useful for efficient inactivation of the aquatic animal pathogenic agents and recycling of the fish waste in an environment-friendly manner.