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Background: This study analyzed data from the end-stage renal disease patient registry collected by the Korean Society of Nephrology to explore trends in mortality among dialysis patients from 2001 to 2022. Methods: Mortality was analyzed in two ways: firstly, using the annual mortality rate; and secondly, by assessing survivability after a certain period of time since the initiation of dialysis. Additionally, we categorized the causes of death by disease group annually to observe how the proportions changed. Results: Since 2001, annual mortality for dialysis patients generally declined, except for a rise in 2020 and 2021 among hemodialysis patients. Overall mortality rates for all dialysis patients dropped from 74.2/1,000 person-years in 2001 to 42.3/1,000 person-years in 2022, with a more pronounced decrease in peritoneal dialysis. While survival probability over the 5 years following initiation of dialysis has shown a steady increase, short-term mortality from 2018 to 2020 affected by coronavirus disease 2019 (COVID-19) has shown a yearly increase by age group, with a greater effect in those aged 75 years and older. The leading causes of death for all dialysis patients have changed little, in the order of heart disease, infection, and vascular problems. Conclusion: While annual mortality and survival probability after dialysis initiation have generally improved in dialysis patients, there has been a temporary deterioration during the COVID-19 pandemic, most pronounced in the elderly.
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Prohibitin 1 (PHB1) is ubiquitously expressed in multiple compartments within cells and is involved in the cell cycle, cell signaling, apoptosis, transcriptional regulation, and mitochondrial biogenesis at the cellular level and in the inflammation-associated and immunological functions of B and T lymphocytes. PHB1 is an important protein that performs antioxidant regulation and immune functions inside and outside cells but has not been sufficiently studied in teleost fish. Our study aimed to elucidate the functional properties and gain new insights into the biological processes and immune system of red seabream (Pagrus major), a commercially important fish cultured in South Korea and East Asia. PHB1 mRNA was most abundantly expressed in the head kidney of healthy red seabream, and significant changes in its expression were observed after artificial infection with bacteria and viruses. On analysis, reporter gene was also significantly upregulated by polyinosinic-polycytidylic acid, lipopolysaccharides, and hydrogen peroxide. Consequent to the functional characterization of PHB1 in cells via recombinant protein preparation, the activity of leukocytes was enhanced and the reactive oxygen species-induced stress in red blood cells was reduced. The results reveal the functional characteristics of PHB1 and provide new insights into the biological processes and immune system of P. major, with beneficial implications in the study of stress responses.
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Doenças dos Peixes , Proteínas de Peixes , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Imunidade Inata , Proibitinas , Proteínas Repressoras , Animais , Proteínas de Peixes/genética , Proteínas de Peixes/imunologia , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Proteínas Repressoras/imunologia , Doenças dos Peixes/imunologia , Imunidade Inata/genética , Regulação da Expressão Gênica/imunologia , Perfilação da Expressão Gênica/veterinária , Poli I-C/farmacologia , Filogenia , Dourada/imunologia , Dourada/genética , Infecções por Vírus de DNA/imunologia , Infecções por Vírus de DNA/veterinária , Sequência de Aminoácidos , Alinhamento de Sequência/veterinária , Lipopolissacarídeos/farmacologia , Perciformes/imunologia , Perciformes/genética , Iridoviridae/fisiologia , Vibrio/fisiologiaRESUMO
Ferredoxin (FDX) is a highly conserved iron-sulfur protein that participates in redox reactions and plays an important role as an electron transport protein in biological processes. However, its function in marine fish remains unclear. We identified two ferrodoxin proteins, FDX1 and FDX2, from black scraper (Thamnaconus modestus) to confirm their genetic structures and expression profiles and to investigate their antimicrobial activity properties by fabricating them with antimicrobial peptides based on sequences. The two TmFDXs mRNAs were most abundant in peripheral blood leukocytes of healthy T. modestus. After artificial infection with Vibrio anguillarum, a major pathogen of T. modestus, TmFDX1 mRNA was significantly upregulated in the gills, heart, intestines, kidneys, liver, and spleen, but was consistently downregulated in the brain. The expression levels of TmFDX2 mRNA were significantly upregulated in the heart, intestines, kidneys, liver, and spleen; however, no significant changes in expression were observed in the brain or gills. Based on the 2Fe-2S ferredoxin-type iron-sulfur-binding domain sequence, two peptides (pFDX1 and pFDX2) were synthesized. The bactericidal effect, biofilm formation inhibition, and gDNA-binding activity of these peptides were investigated. These findings highlight the potential as a natural peptide candidate for TmFDXs.
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Sequência de Aminoácidos , Peptídeos Antimicrobianos , Ferredoxinas , Doenças dos Peixes , Proteínas de Peixes , Vibrioses , Vibrio , Animais , Proteínas de Peixes/genética , Proteínas de Peixes/química , Proteínas de Peixes/imunologia , Doenças dos Peixes/imunologia , Vibrio/fisiologia , Peptídeos Antimicrobianos/química , Peptídeos Antimicrobianos/farmacologia , Peptídeos Antimicrobianos/genética , Ferredoxinas/genética , Ferredoxinas/química , Vibrioses/veterinária , Vibrioses/imunologia , Imunidade Inata/genética , Alinhamento de Sequência/veterinária , Perfilação da Expressão Gênica/veterinária , Filogenia , Regulação da Expressão Gênica/efeitos dos fármacos , Perciformes/imunologia , Perciformes/genéticaRESUMO
Red sea bream iridovirus (RSIV) is a highly contagious viral infection that affects various fish species and poses a significant threat to the global aquaculture industry. Thus, accurate and timely diagnosis is paramount for sustainable management of fish health. This study rigorously evaluated the diagnostic efficacy of various polymerase chain reaction (PCR) assays, focusing on those recommended by the World Organization for Animal Health (WOAH) and the assays newly proposed by WOAH's Aquatic Animals Health Standards Commission. Specifically, this study assessed conventional PCR, nested PCR, modified 1-F/1-R, and real-time PCR assays using a 95% limit of detection (LoD95%), as well as diagnostic sensitivity (DSe) and specificity (DSp) tests across different RSIV severity grades (G0-G4). In previous studies, the LoD95% for the 1-F/1-R and 4-F/4-R conventional assays were 225.81 and 328.7 copies/reaction, respectively. The modified 1-F/1-R exhibited a lower LoD95% of 51.32 copies/reaction. Notably, the nested PCR had an LoD95% of 11.23 copies/reaction, and the real-time PCR assay had an LoD95% of 12.02 copies/reaction. The DSe varied across RSIV severity grades, especially in the lower G0-G2 grades. The nested PCR and modified 1-F/1-R assays displayed the highest DSe, making them particularly useful for early-stage screening and detection of asymptomatic carriers. In addition, the PCR assays did not cross-react with any other aquatic pathogens except RSIV. Our findings significantly advanced the diagnostic capabilities of RSIVD by suggesting that nested PCR and modified 1-F/1-R assays are particularly promising for early detection. We propose their inclusion in future WOAH guidelines for a more comprehensive diagnostic framework.
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Doenças dos Peixes , Iridovirus , Dourada , Viroses , Animais , Iridovirus/genética , Reação em Cadeia da Polimerase em Tempo Real/veterináriaRESUMO
BACKGROUND: Salinomycin, an antibiotic, have potential as a veterinary drug for fish due to its anti-parasitic activity against several fish parasites. Thus the residual levels of salinomycin in muscles of two significant aquaculture species in Korea, olive flounder and black rockfish, were analyzed using HPLC-MS-MS. RESULTS: The proper method to analyze the residual salinomycin in fish muscles using LC-MS-MS was settled and the method was validated according to CODEX guidelines. The residues in three distinct groups for two fish species were analyzed using the matrix match calibration curves at points of five different times following oral administration. After oral administration, salinomycin rapidly breaks down in both olive flounder and black rockfish. After 7th days, the average residue in all groups of two fish spp. decreased below limit of quantitation (LOQ). CONCLUSION: Due to low residue levels in fish muscles, salinomycin may therefore be a treatment that is safe for both fish and humans. This result could contribute to establishment of MRL (minimal residual limit) for approval of salinomycin for use in aquaculture.
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Doenças dos Peixes , Linguado , Perciformes , Policetídeos de Poliéter , Piranos , Humanos , Animais , Doenças dos Peixes/tratamento farmacológico , Doenças dos Peixes/parasitologia , Peixes , Músculos/parasitologia , Administração OralRESUMO
This study detected two potential pathogens, Vibro parahaemolyticus, which causes acute hepatopancreatic necrosis disease (AHPND), and white spot syndrome virus (WSSV), in fishing bait in South Korea. However, their infectious nature was not confirmed, possibly due to the degradation caused by freezing/thawing or prolonged storage under frozen conditions. While infectivity was not confirmed in this study, there is still a significant risk of exposure to these aquatic products. Furthermore, fishing bait and feed should be handled with caution as they are directly exposed to water, increasing the risk of disease transmission. In Australia, cases of WSSV infection caused by imported shrimp intended for human consumption have occurred, highlighting the need for preventive measures. While freezing/thawing is a method for inactivating pathogens, there are still regulatory and realistic issues to be addressed.
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Aquaculture, a crucial sector of the global food industry, faces a myriad of issues due to parasitic invasions. One such parasite, Microcotyle sebastis, which afflicts Korean rockfish in South Korea, has a significant economic impact. The impending danger of resistance to traditional anthelmintics necessitates the exploration of new antiparasitic candidates. Although the efficacy of salinomycin against aquatic parasites such as ciliates and sporozoans is known, its influence on monogeneans has yet to be studied. Therefore, this study investigated the efficacy and safety of salinomycin for the treatment of M. sebastis infections, presenting the first exploration of salinomycin's therapeutic potential against monogeneans. In vitro examinations revealed a minimum effective concentration of salinomycin of 5 mg/kg, which led to necrosis of the haptor upon dislodging from the gill filaments. The one-time oral administration of the drug at concentrations of 5 mg/kg and 10 mg/kg showed a significant dose-dependent reduction in parasite counts, with no apparent behavioral side effects in Korean rockfish. Biochemical analyses monitored the liver, heart, and kidney enzymes, specifically aspartate transaminase (AST), alanine transaminase (ALT), blood urea nitrogen (BUN), and creatine kinase-myocardial band (CK-MB). At both 20 °C and 13 °C, no significant differences were observed in the levels of AST and ALT. However, at 20 °C, alterations in BUN levels were evident on Day 14, a deviation not observed at 13 °C. The CK-MB analysis revealed elevated enzyme levels at both temperatures when compared to the control group, reflecting the similar changes observed in terrestrial animals administered salinomycin. The biochemical data suggest that the oral administration of salinomycin is potentially more favorable at 13 °C than at 20 °C. Although our findings warrant further comprehensive studies, including on the long-term and potential effects on nontarget species and water quality, they also suggest that salinomycin could be considered as an alternative or adjunctive treatment if resistance to the currently used praziquantel against M. sebastis is confirmed.
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Flavobacterium psychrophilum is the causative agent of bacterial cold-water disease in salmonids and rainbow trout fry syndrome. This pathogen has attained a global presence and can spread both horizontally and vertically. However, it was not documented in Korea before September 2018. In this study, the objectives were to characterize Flavobacterium psychrophilum strain FPRT1, isolated from diseased rainbow trout genotypically and phenotypically. We also conducted various investigations to better understand its impact and assess potential control measures. We acquired fifty rainbow trout (approximately 70 g in weight) and transferred them to a laboratory aquarium. During the initial acclimation period, we observed mortality and examined affected fish for clinical signs. We isolated the bacterium from the spleen of infected rainbow trout using tryptone yeast extract salts agar supplemented with glucose, naming this FPRT1. Antibiotic susceptibility testing was carried out, and from the result, we selected enrofloxacin to administer to the trout orally to reduce mortality. To evaluate pathogenicity, we exposed the trout to FPRT1 at different water temperatures (8, 15, and 22 °C). Genomic analysis was conducted to identify the serotype and relatedness of FPRT1 to European strains. Affected fish displayed clinical signs, such as ulcerative lesions in the mandible, anemia with pale gills, exophthalmia, and increased mucus secretion. Internal symptoms included pale liver and enlarged spleen. FPRT1 was susceptible to erythromycin, enrofloxacin, florfenicol, oxytetracycline, and gentamicin, but resistant to oxolinic acid and sulfamethoxazole/trimethoprim. Oral administration of enrofloxacin resulted in a decrease in mortality from 28% to 6%. Pathogenicity tests revealed varying mortality rates due to FPRT1 at different temperatures. The highest rates were observed at 8 °C (ranging from 43% to 100%) for both intraperitoneal and intramuscular injections, and lower rates occurred at 22 °C (ranging from 0% to 30%), with intramuscular injections displaying higher susceptibility. Genomic analysis identified FPRT1 as serotype 2 and indicated its close genetic relationship with European strains based on the core genome and dispensable genome. The substantial genomic similarity between our strain and European strains suggests the possibility of bacterial spread through the importation of fertilized eggs from Europe. In conclusion, this study highlights the introduction of the previously undocumented pathogen (F. psychrophilum) into Korean rainbow trout populations. The detection of this pathogen and its pathogenicity assessment is not only important for understanding its impact on local aquaculture but also for establishing surveillance and control measures to prevent further transmission and outbreaks in the region.
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Parasitic infections pose significant challenges in aquaculture, and the increasing resistance to conventional anthelmintics necessitates the exploration of alternative treatments. Levamisole hydrochloride (HCl) has demonstrated efficacy against monogenean infections in various fish species; however, research focused on Microcotyle sebastis infections in Korean rockfish (Sebastes schlegelii) remains limited. Therefore, this study aimed to evaluate the efficacy of levamisole HCl against M. sebastis infections in Korean rockfish with the goal of optimizing anthelmintic usage in aquaculture. In this study, we first assessed the susceptibility of M. sebastis to levamisole HCl in vitro. Subsequently, in vivo evaluations were conducted to assess the drug's efficacy, safety, and to identify optimal administration methods. In vitro experiments revealed concentration-dependent sensitivity of M. sebastis to levamisole HCl, with a minimum effective concentration (MEC) of 100 mg/L. In vivo experiments employed oral administration, intraperitoneal injection, and immersion treatments based on the MEC. Oral administration proved to be a safe method, yielding efficacy rates of 27.3% and 41.6% for 100 mg/kg and 200 mg/kg doses, respectively, in contrast to the immersion and injection methods, which induced symptoms of abnormal swimming, vomiting, and death. Biochemical analyses conducted to assess the safety of levamisole HCl revealed a transient, statistically significant elevation in the levels of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) on day three post-administration at 20 °C. Following this, no substantial differences were observed. However, at 13 °C, the enzyme levels remained relatively consistent, emphasizing the role of water temperature conditions in influencing the action of levamisole HCl. Our research findings substantiate the efficacy of levamisole HCl against M. sebastis in Korean rockfish, underscoring its potential for safe oral administration. These results provide valuable insights for developing parasite control strategies involving levamisole HCl in Korean rockfish populations while minimizing adverse impacts on fish health and the environment. However, this study bears limitations due to its controlled setting and narrow focus. Future research should expand on these findings by testing levamisole HCl in diverse environments, exploring different administration protocols, and examining wider temperature ranges.
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In this study, the starry flounder L1 cell adhesion molecule (L1CAM) sequence was obtained using next-generation sequencing, and the integrity of the sequence was verified by cloning and sequencing. First, the amino acid sequence was predicted using the cDNA sequence, and the gene was then identified through multiple sequence alignment analysis with related sequences and phylogenetic analysis. Thus, homogeneity was confirmed. The expression level of PsL1CAM (Platichthys stellatus L1CAM) mRNA in healthy starry flounder was detected in all tissues used in the experiment, and tissue- and gene-specific expression levels were confirmed. In addition, as a result of mRNA expression analysis after artificial infection with viral hemorrhagic septicemia virus (VHSV) and Streptococcus parauberis PH0710, significant expression changes and characteristics were confirmed following infection with VHSV and S. parauberis PH0710. After artificial infection with VHSV, the expression level of PsL1CAM mRNA was significantly upregulated in almost all major tissues of the starry flounder, whereas it was significantly downregulated in mucosal-associated lymphoid tissues, such as the gills and intestine. Infection with S. parauberis PH0710 significantly upregulated the expression of PsL1CAM mRNA in almost all major tissues of the starry flounder, whereas it was significantly downregulated in the heart after infection. Our results indicate that PsL1CAM may be involved in the host immune response to starry flounders.
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In recent years, studies have highlighted the significant impact of probiotic treatment on the central nervous system (brain) and stress regulation through the microbiota-gut-brain axis, yet there have been limited knowledge on this axis in fish. Therefore, this study aimed to enhance the current understanding of the mechanisms underlying probiotic effects on neurotransmission and stress alleviation in fish through transcriptomic profiling. In this study, olive flounders (Paralichthys olivaceus) were subjected to two trial setups: a 1-month lab-scale trial and a 6-month field-scale trial, with and without the probiotic strain Lactococcus lactis WFLU12. RNA-Seq analysis was performed using liver samples collected from fish at one-month post-feeding (mpf) in both trials. Additionally, fish growth was monitored monthly, and serological parameters were measured at one mpf in the field-scale experiment. The results of the lab-scale trial showed that probiotic administration significantly upregulated genes related to neurotransmission, such as htr3a, mao, ddc, ntsr1, and gfra2. These findings highlight the impact of probiotics on modulating neurotransmission via the microbiota-gut-brain axis. In the field-scale experiment, fish growth was significantly promoted and the sera levels of AST, LDH, and cortisol were significantly higher in the control group compared to the probiotics group. Furthermore, genes involved in stress responses (e.g. hsp70, hsp90B1, hspE1, prdx1, and gss) and transcriptional regulators (e.g. fos, dusp1, and dusp2) exhibited significant upregulation in the control group compared to the probiotics group, indicating that probiotic administration can alleviate stress levels in fish. Overall, this study provides valuable insights into the mechanisms underlying the beneficial effects of probiotics in fish, specifically regarding their impact on neurotransmission and stress alleviation.
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Linguado , Probióticos , Animais , Transcriptoma , Probióticos/farmacologia , Perfilação da Expressão Gênica/veterinária , Transmissão SinápticaRESUMO
Streptococcus parauberis is the dominant etiological agent of streptococcosis, the most devastating bacterial disease in the olive flounder farming industry in South Korea. In this study, the distribution of serotypes, antimicrobial susceptibility, and presence of antimicrobial resistance genes (ARGs) in S. parauberis isolates obtained between 1999 and 2021 was thoroughly investigated to gain insight into the dynamics of their presence and the relationship between serotypes and antimicrobial resistance. Disk diffusion testing of 103 isolates against 10 antimicrobial agents was performed, and epidemiological cut-off values generated through normalized resistance interpretation analysis were used to classify wild-type (WT) and non-wild-type (NWT) populations. Principal component analysis and hierarchical clustering were implemented to achieve an understanding on the relationship between serotypes and antimicrobial resistance patterns. PCR-based serotyping showed that serotype Ia (67.1%) was the most prevalent in South Korea, followed by serotypes Ib/Ic (25.2%) and II (7.7%). The highest proportion of isolates was assigned to NWT against amoxicillin (80.6%), followed by oxytetracycline (77.7%) and erythromycin (48.5%). The time-scale data showed that recently obtained serotypes Ib/Ic and II isolates tended to be categorized as NWT populations resistant to more antibiotics, possibly due to microbial adaptation to antibiotic pressure. ARGs responsible for resistance to oxytetracycline and erythromycin were found only in NWT populations in serotype Ia [tet(S) and erm(B), respectively], and serotype II [tet(M) and mef(J)-msr(I), respectively]. We also found that the mef-msr gene pair in S. parauberis serotype II might be involved in low-level resistance to erythromycin. IMPORTANCE This study presents serotype distribution and antimicrobial susceptibility data along with the antimicrobial resistance genes (ARGs) of Streptococcus parauberis, which is an important bacterial fish pathogen worldwide. In particular, almost all oxytetracycline and erythromycin non-wild-type (NWT) populations harbored tet(S) or tet(M), and erm(B) or mef(J)-msr(I), respectively. Interestingly, these ARGs were distributed in a highly serotype-dependent manner, resulting in a clear correlation between the antibiogram and serotype distribution. Moreover, recent isolates belonging to serotypes Ib/Ic and II tended to be more frequently categorized as NWT against antimicrobials, including amoxicillin and cefalexin compared to old isolates, while a dramatic decrease in erythromycin and clindamycin NWT frequencies was observed in recent serotype Ia isolates, which lacked erm(B). These variations might be attributed to shifts in the antibiotics employed in South Korean aquaculture over time. The overall findings would provide important background knowledge for understanding the epidemiology of S. parauberis infection in aquaculture.
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Infestations of parasites, particularly those caused by copepods and monogeneans, are a major hindrance to aquaculture and have a big negative economic impact. Sebastes schlegelii, a farmed Korean rockfish, is particularly prone to copepods and monogeneans. This study comprehended how parasitic copepods and rockfish from a farm in Tongyeong-si, Gyeongsangnam-do, Korea, are related to the monogenean trematode Microcotyle sebastis. Our research revealed that monogeneans predominated, with a rate of 98.4% and an average infection intensity of 7 per infected fish. With an average infection intensity of 4 per sick fish, the infection rate for parasitic copepods was equally considerable, coming in at 91.7%. The high co-infection rate of both parasite families, at 90.8%, is noteworthy. Furthermore, Lepeophtheirus elegans and Peniculus truncatus, 2 parasitic copepod species, were discovered to have M. sebastis eggs attached to their bodies. This demonstrates a connection between parasitic copepod infestations in farmed Korean rockfish and the monogenean trematode M. sebastis. These discoveries highlight the necessity for creating more potent parasite control methods for the aquaculture sector and shed light on the intricate relationships between various parasite species.
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Copépodes , Parasitos , Perciformes , Trematódeos , Animais , Pesqueiros , República da Coreia/epidemiologiaRESUMO
The oomycete Aphanomyces invadans causes epizootic ulcerative syndrome (EUS), a World Organization for Animal Health (WOAH)-listed disease that has seriously impacted a wide range of fish worldwide. Currently, only three conventional polymerase chain reaction (PCR) assays are recommended for the detection of A. invadans. The robust quantitative PCR (qPCR) assay has recently become more important due to its highly accurate nature and the applicability of qPCR-based environmental DNA (eDNA) detection in the monitoring of pathogens in aquatic environments. Therefore, in this study, we developed a novel TaqMan probe-based qPCR method to sensitively and quantitatively detect A. invadans. The assay limit of detection was determined using 10-fold serial dilutions of linearized A. invadans plasmid. Assay sensitivity was assessed in the presence of interfering substances and compared to three WOAH-listed primers using the mycelia and zoospores of A. invadans with and without fish muscle tissue. The assay specificity was also theoretically and experimentally assessed against other oomycetes, fish muscle tissue, and water samples. The assay's repeatability and reproducibility were determined. In this study, the limit of detection of the developed assay was 7.24 copies of A. invadans genomic DNA per reaction (95% confidence interval (CI): 2.75 to 19.05 copies/reaction). The assay showed the same sensitivity in the presence of other substances. Compared to the WOAH-recommended PCR assays, this assay had 10-times higher sensitivity for all tested samples. There were no cross-reactions with other closely related oomycetes, fish muscle, or water samples, indicating that the assay was highly specific for A. invadans. The repeatability and reproducibility tests showed little variation, ranging from 0.1-0.9% and 0.04-1.1%, respectively, indicating the high consistency, repeatability, and reliability of the developed assay. This highly rapid, sensitive, specific, and consistent EUS qPCR assay would be of importance in transboundary disease management and the monitoring of pathogens in aquatic environments.
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Aphanomyces , Doenças dos Peixes , Oomicetos , Animais , Aphanomyces/genética , Reprodutibilidade dos Testes , Peixes , Água , Doenças dos Peixes/diagnósticoRESUMO
Climate change is one of the most important threats to farmed abalone worldwide. Although abalone is more susceptible to vibriosis at higher water temperatures, the molecular mode of action underlying this has not been fully elucidated. Therefore, this study aimed to address the high susceptibility of Halitotis discus hannai to V. harveyi infection using abalone hemocytes exposed to low and high temperatures. Abalone hemocytes were divided into four groups, 20C, 20 V, 25C, and 25 V, depending on co-culture with (V)/without (C) V. harveyi (MOI = 12.8) and incubation temperature (20 °C or 25 °C). After 3 h of incubation, hemocyte viability and phagocytic activity were measured, and RNA sequencing was performed using Illumina Novaseq. The expression of several virulence-related genes in V. harveyi was analyzed using real-time PCR. The viability of hemocytes was significantly decreased in the 25 V group compared to cells in the other groups, whereas phagocytic activity at 25 °C was significantly higher than at 20 °C. Although a number of immune-associated genes were commonly upregulated in abalone hemocyte exposed to V. harveyi, regardless of temperature, pathways and genes regarding pro-inflammatory responses (interleukin-17 and tumor necrosis factor) and apoptosis were significantly overexpressed in the 25 V group compared to the 25C group. Notably, in the apoptosis pathway, genes encoding executor caspases (casp3 and casp7) and pro-apoptotic factor, bax were significantly up-regulated only in the 25 V group, while the apoptosis inhibitor, bcl2L1 was significantly up-regulated only in the 20 V group compared to the control group at the respective temperatures. The co-culture of V. harveyi with abalone hemocytes at 25 °C up-regulated several virulence-related genes involved in quorum sensing (luxS), antioxidant activity (katA, katB, and sodC), motility (flgI), and adherence/invasion (ompU) compared to those at 20 °C. Therefore, our results showed that H. discus hannai hemocytes exposed to V. harveyi at 25 °C were highly stressed by vigorously activated inflammatory responses and that the bacterial pathogen overexpressed several virulence-related genes at the high temperature tested. The transcriptomic profile of both abalone hemocytes and V. harveyi in the present study provide insight into differential host-pathogen interactions depending on the temperature conditions and the molecular backgrounds related to increased abalone vulnerability upon global warming.
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Gastrópodes , Vibrioses , Vibrio , Animais , Temperatura , Vibrio/fisiologia , Gastrópodes/genéticaRESUMO
Red sea bream iridovirus (RSIV) causes significant economic losses in aquaculture. Here, we analyzed the pathogenicity, viral shedding, and transmission dynamics of RSIV in rock bream (Oplegnathus fasciatus) by employing immersion infection and cohabitation challenge models. Rock bream challenged by immersion exposure exhibited 100% mortality within 35 days post RSIV exposure, indicating that the viral shedding in seawater peaked after mortality. At 25 °C, a positive correlation between the viral loads within infected rock bream and virus shedding into the seawater was observed. Specific RSIV lesions were observed in the spleen and kidney of the infected rock bream, and the viral load in the spleen had the highest correlation with the histopathological grade. A cohabitation challenge mimicking the natural transmission conditions was performed to assess the virus transmission and determine the pathogenicity and viral load. The RSIV-infected rock breams (donors) were cohabited with uninfected rock bream, red sea bream (Pagrus major), and flathead grey mullet (Mugil cephalus) (recipients) at both 25 °C and 15 °C. In the cohabitation challenge group maintained at 15 °C, no mortality was observed across all experimental groups. However, RSIV was detected in both seawater and the recipient fish. Our results provide preliminary data for further epidemiological analyses and aid in the development of preventive measures and management of RSIVD in aquaculture.
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Red sea bream iridovirus (RSIV) causes significant economic losses in the aquaculture industry. We analyzed the pathogenicity of RSIV in flathead grey mullets (Mugil cephalus), the correlation of histopathological lesions, and interspecies horizontal transmission, through immersion infection and cohabitation challenges. Flathead grey mullets, which were challenged by immersion infection, exhibited mortality at 14 and 24 days after RSIV exposure. Viral shedding in seawater peaked 2-3 days before or after the observed mortality. Specific lesions of RSIV were observed in the spleen and kidney, and the correlation between histopathological grade and viral load was the highest in the spleen. In a cohabitation challenge, flathead grey mullets were the donors, and healthy rock bream, red sea bream, and flathead grey mullets were the recipients. Viral shedding in seawater was the highest in flathead grey mullet and rock bream at 25 °C, with 106.0 RSIV copies L/g at 14 dpi. No mortality was observed in any group challenged at 15 °C, and no RSIV was detected in seawater after 30 dpi. The virus shed from RSIV-infected flathead grey mullets caused horizontal transmission through seawater. These findings suggest that rapid decision-making is warranted when managing disease in fish farms.
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Red sea bream iridovirus (RSIV) is an important aquatic virus that causes high mortality in marine fish. RSIV infection mainly spreads through horizontal transmission via seawater, and its early detection could help prevent disease outbreaks. Although quantitative PCR (qPCR) is a sensitive and rapid method for detecting RSIV, it cannot differentiate between infectious and inactive viruses. Here, we aimed to develop a viability qPCR assay based on propidium monoazide (PMAxx), which is a photoactive dye that penetrates damaged viral particles and binds to viral DNA to prevent qPCR amplification, to distinguish between infectious and inactive viruses effectively. Our results demonstrated that PMAxx at 75 µM effectively inhibited the amplification of heat-inactivated RSIV in viability qPCR, allowing the discrimination of inactive and infectious RSIV. Furthermore, the PMAxx-based viability qPCR assay selectively detected the infectious RSIV in seawater more efficiently than the conventional qPCR and cell culture methods. The reported viability qPCR method will help prevent the overestimation of red sea bream iridoviral disease caused by RSIV. Furthermore, this non-invasive method will aid in establishing a disease prediction system and in epidemiological analysis using seawater.
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Doenças dos Peixes , Iridovirus , Dourada , Animais , Iridovirus/genética , Dourada/genética , Propídio , Reação em Cadeia da PolimeraseRESUMO
Red sea bream iridoviral disease (RSIVD) causes serious economic losses in the aquaculture industry. In this paper, we evaluated RSIV kinetics in rock bream under various rearing water temperatures and different RSIV inoculation concentrations. High viral copy numbers (approximately 103.7-106.7 RSIV genome copies/L/g) were observed during the period of active fish mortality after RSIV infection at all concentrations in the tanks (25 °C and 20 °C). In the group injected with 104 RSIV genome copies/fish, RSIV was not detected at 21-30 days post-infection (dpi) in the rearing seawater. In rock bream infected at 15 °C and subjected to increasing water temperature (1 °C/d until 25 °C) 3 days later, the virus replication rate and number of viral copies shed into the rearing seawater increased. With the decrease in temperature (1 °C/d) from 25 to 15 °C after the infection, the virus replicated rapidly and was released at high loads on the initial 3-5 dpi, whereas the number of viral copies in the fish and seawater decreased after 14 dpi. These results indicate that the number of viral copies shed into the rearing seawater varies depending on the RSIV infection level in rock bream.
RESUMO
Interleukin-1 beta (IL-1ß) is transcribed by monocytes, macrophages, and dendritic cells in response to activation of toll-like receptors (TLRs) by pathogen-associated molecular patterns (PAMPs) or cytokine signalling and causes a rapid inflammatory response to infection. IL-8, also known as chemokine C-X-C motif ligand (CXCL)-8, is regulated by IL-1ß and affects the chemotaxis of macrophages and neutrophils upon pathogen infection. In healthy red sea bream, rsbIL-1ß is most highly distributed in the liver, and rsbIL-8 is most highly distributed in the head kidney. In response to RSIV infection, rsbIL-1ß and rsbIL-8 mRNA are significantly upregulated in the kidney and spleen. This may be because the primary infection targets of RSIV are the kidney and spleen. In the gills, both genes were significantly upregulated at 7 days after RSIV infection and may be accompanied by a cytokine storm. In the liver, both genes were significantly downregulated at most observation points, which may be because the immune cells such as macrophages and dendritic cells expressing rsbIL-1ß or rsbIL-8 migrated to other tissues because the degree of RSIV infection was relatively low. Using a GFP fusion protein, it was confirmed that rsbIL-1ß and rsbIL-8 were localized to the cytoplasm of Pagrus major fin (PMF) cells. RsbIL-1ß overexpression induced the expression of interferon gamma (IFN-γ), myxovirus-resistance protein (Mx) 1, IL-8, IL-10, TNF-α, and MyD88, while rsbIL-8 overexpression induced the expression of IFN-γ, Mx1, rsbIL-1ß and TNF-α. In addition, overexpression of both genes significantly reduced the genome copies of RSIV and significantly reduced the viral titers. Therefore, rsbIL-1ß and rsbIL-8 in red sea bream play an antiviral role against RSIV through their normal signalling.