Search Results (112)

Triplophysa siluroides, a unique species of plateau fish, holds significant economic value. However, its natural population has sharply declined due to overfishing and the construction of water conservancy projects. Investigating the various conditions necessary for its growth is a crucial prerequisite for successful artificial breeding. This study used Edwardsiella tarda as the pathogenic bacterium to determine the median lethal concentration following infection of T. siluroides, as well as to examine changes in tissues, organs, and gene expression. The study found that dead T. siluroides displayed symptoms such as abdominal distension, fluid accumulation, and a reddened anus, and the median lethal concentration of E. tarda for T. siluroides was calculated to be 1.00 × 10⁶ CFU/mL. Following infection with E. tarda, the liver, intestine, gills, spleen, and kidneys exhibited varying degrees of lesions. Transcriptome sequencing identified a total of 54,667 genes. Compared to the blank control group, 192 genes were downregulated and 125 genes were upregulated in T. siluroides infected with E. tarda. In contrast, after infection with the poly(I:C) viral mimic, 225 genes were downregulated and 436 genes were upregulated. This study determined the median lethal concentration of E. tarda for T. siluroides via intraperitoneal injection under laboratory conditions. The results may contribute to disease prevention and control in the breeding of T. siluroides, as well as inform future risk assessments of infection in aquaculture water bodies. Full article

The Nipponia nippon is a critically endangered species, and its breeding efforts are of vital importance for its conservation. Although artificial shell removal is sometimes employed in current breeding programs to increase survival rates, it may also have unknown impacts on chicks’ development. To investigate the influence of artificial shell removal on the gut microbiota composition in Nipponia nippon, metagenomic sequencing and untargeted LC-MS/MS analyses were performed. Samples from the early, mid, and late stages of natural hatching (ZE, ZM, ZL) and artificial shell removal (RE, RM, RL) were compared. Results indicated that the natural hatching groups formed a unique, highly diverse, and stable community by the late stage (ZL). Conversely, artificial peeling caused the microbial community succession to stagnate at an intermediate state. The RL group experienced a sharp decline in alpha diversity and a significant enrichment of opportunistic pathogens, such as Edwardsiella, Clostridium, and Fusobacterium. Functionally, the microbial community in the RL group remained in a stage of expanding basic functions rather than reaching an advanced equilibrium state. Metabolomic analysis confirmed this developmental arrest, revealing abnormal accumulations of organic acids, such as citric acid, and indole derivatives in the RL group. This indicates metabolic dysregulation, stress, and altered microbial–host chemical signaling. Furthermore, the significant biomarker Edwardsiella was strongly correlated with multiple differential metabolites in the RL group. Ultimately, these results indicate that artificial peeling intervention disrupts environmental adaptation and induces metabolic alterations in the intestinal development of the Nipponia nippon chicks. Full article

Background: Edwardsiella piscicida is a significant intracellular pathogen of channel catfish (Ictalurus punctatus) and a major threat to U.S. aquaculture. A recently developed recombinant attenuated vaccine strain (χ16016) uses arabinose-regulated murA expression to trigger delayed cell wall lysis in vivo, ensuring biological containment while conferring strong protection against virulent challenge. Although its efficacy has been demonstrated, the host immune programs underlying protection remain incompletely defined. Methods: We used RNA sequencing to characterize tissue-specific transcriptomic responses in the intestines and kidneys of channel catfish at 7 days post-vaccination. Fish were vaccinated with χ16016 by either bath immersion or intracoelomic (IC) injection, and differentially expressed genes and enriched immune pathways were analyzed to determine how the vaccine delivery route shapes systemic and mucosal immune responses. Results: Across comparisons, 19,101 differentially expressed genes revealed pronounced route- and tissue-dependent immune remodeling. As aquaculture vaccination strategies increasingly prioritize scalability and practical deployment, understanding how the delivery route shapes immune outcomes is critical. Here, IC vaccination induced broader systemic transcriptional changes, particularly in the intestine, whereas bath immunization elicited a more focused yet coordinated mucosal response. Overall, intestinal tissue exhibited greater transcriptional responsiveness than kidney tissue, underscoring its central role in early vaccine-induced immunity. Functional enrichment analyses identified the activation of innate recognition pathways, MAPK and calcium signaling cascades, complement components, antigen processing machinery, and cell adhesion networks. Notably, bath immunization enriched the intestinal immune network for IgA production pathway, which represents an orthology-based mapping of conserved mucosal immune components, alongside the upregulation of IL-6, CXCL12–CXCR4, integrins (α4β7), MHC class II, complement C3, and polymeric immunoglobulin receptor (pIgR). Given that catfish rely primarily on IgM in mucosal immunity, these findings indicate the induction of IgM-mediated mucosal defense rather than classical mammalian IgA responses. Concurrent complement and scavenger receptor signatures suggest a transition toward efficient opsonophagocytic clearance with controlled inflammation at this subacute stage. Conclusions: This study provides the first systems-level view of host transcriptomic responses to a regulated-lysis E. piscicida vaccine in channel catfish. The findings demonstrate that immersion vaccination, although transcriptionally less expansive than injection, effectively activates coordinated mucosal innate and adaptive immune programs, supporting its practical use as a scalable vaccination strategy for aquaculture. Full article

This study evaluated the potential of pomegranate (Punica granatum) juice byproducts (PJB) as a functional dietary additive for juvenile red seabream (Pagrus major). Four experimental diets were formulated to contain various levels of PJB (0, 2.5, 5.0, and 10.0 g/kg) and fed to fish with an initial body weight of 7.0 ± 0.01 g for 8 weeks. Growth performance, feed utilization, digestive enzyme activity, whole-body composition, plasma biochemical parameters, antioxidant responses, immune parameters, and resistance to Edwardsiella tarda infection were evaluated. Fish fed the diet containing 2.5 g/kg PJB exhibited significantly higher final body weight, weight gain, and specific growth rate compared with the control group and those with higher PJB doses, whereas feed intake, feed efficiency, and protein efficiency ratio were not significantly affected by dietary treatment. Intestinal trypsin and lipase activities were significantly elevated in the PJB2.5 group, whereas amylase activity remained unchanged. Whole-body proximate composition and plasma biochemical parameters, including aspartate aminotransferase, alanine aminotransferase, total cholesterol, glucose, and total protein, were not significantly influenced by dietary PJB supplementation. Dietary inclusion of PJB at 2.5 g/kg also significantly enhanced plasma antioxidant enzyme activities, as evidenced by increased superoxide dismutase and glutathione levels, while catalase activity was elevated in fish fed the PJB2.5 and PJB5 diets. Innate immune responses were also stimulated, with significantly higher serum lysozyme activity and interleukin-1 levels observed in fish fed the PJB2.5 diet. Following experimental challenge with E. tarda, fish fed diets containing 2.5 and 5.0 g/kg PJB exhibited significantly higher cumulative survival than the control group. In conclusion, dietary supplementation with PJB at 2.5 g/kg improved growth performance, digestive capacity, antioxidant status, innate immune responses, and disease resistance in juvenile P. major without adverse physiological effects. Full article

The impacts of dietary xylooligosaccharide (XOS) were explored on growth, blood biochemistry, immune response, and resilience of olive flounder (Paralichthys olivaceus) against Edwardsiella tarda. Three replicate groups of fish (47.2 ± 0.41 g) were fed four diets incorporating various doses of XOS [0% (control), 1%, 2%, and 3%] to apparent satiety for eight weeks. Dietary inclusion of XOS improved growth performance and increased hepatosomatic and viscerosomatic indices. Serum alanine aminotransferase activity decreased with XOS supplementation, indicating improved liver status. Key innate immune parameters, including serum lysozyme, antiprotease, and alternative complement (ACH50) activities, were enhanced in XOS-fed fish. Skin mucus protein content also increased, whereas serum myeloperoxidase and glutathione peroxidase activities, as well as skin mucus antiprotease and protease activities, remained unchanged. XOS supplementation modulated serum bacteriostatic activity against non-pathogenic Escherichia coli and altered skin mucus lectin-binding patterns. Validation of the enhanced immune competence was confirmed by the enhancement of fish survival rate after exposure to E. tarda. Overall, the results demonstrate that dietary XOS, particularly at 3% inclusion, is effective in enhancing innate immunity and disease tolerance in olive flounder. Full article

Antimicrobial resistance in bacteria associated with aquaculture, such as Edwardsiella spp., represents an emerging challenge because of their relevance to fish health and their potential impact on animal, environmental, and human health. In this study, we primarily investigated the antimicrobial susceptibility profiles of Edwardsiella anguillarum isolated from farmed Nile tilapia (Oreochromis niloticus) in Brazil. Based on our findings, herein, we propose provisional local epidemiological cut-off values (pECVs) using the normalized resistance interpretation method, with data for Edwardsiella tarda included as an exploratory context. Fifty isolates (31 E. anguillarum and 19 E. tarda) collected between 2017 and 2025 were tested against 28 antibacterial agents using the disk diffusion method. Based on the pECVs, isolates were classified as wild type (WT) or non-WT (NWT), and the multiple antibiotic resistance (MAR) index was calculated. Most E. anguillarum isolates remained susceptible to several classes, although NWT and multidrug-resistant profiles were detected with a MAR index of 0.68, suggesting selective pressure in intensive tilapia farming systems. These findings support the use of local, species-specific pECVs for resistance surveillance in aquaculture, highlighting the importance of continuous antimicrobial resistance monitoring in aquaculture from a One Health perspective. Full article

While striped catfish (Pangasianodon hypophthalmus) is an economically important aquaculture species, its genomic resources remain limited. To date, linkage maps, QTL (quantitative trait loci) analyses, and the identification of candidate genes associated with disease resistance traits are very limited. Therefore, the present study aimed to construct a high-density linkage map and identify candidate genes for this species. Our analysis was conducted on a pedigree population consisting of 560 individuals (490 offspring and 70 parents for 40 families), whose genomes were analyzed using a genotyping-by-sequencing platform. After stringent filtering, 9882 high-quality SNPs were retained for linkage analysis. Linkage analysis placed 8786 markers onto 30 linkage groups (LGs), with an average density of 0.43 SNPs per cM. Recombination rates varied across the 30 linkage groups (LGs), averaging of 3.6 cM/Mb in males, 6.7 cM/Mb in females, and 5.1 cM/Mb when sex-averaged. Using the linkage map, our QTL analysis identified three significant QTLs for disease resistance to Edwardsiella ictaluri, the causative agent of Bacillary Necrosis of Pangasius (BNP). The QTLs were located on LG1, LG9 and LG29, and their peak markers explained 17.03% of the phenotypic variance. An LD-based interval of approximately ±25 kb surrounding the QTL peak was identified as the putative candidate region. However, subsequent genome-wide association analysis did not identify significant SNP effects within these regions, suggesting that the QTLs may represent polygenic or small-effect loci that are detectable only in linkage-based analyses. In summary, this study presents the first high-density SNP-based linkage map for striped catfish and reports significant QTL and associated candidate genes related to disease resistance and growth traits. These findings provide valuable insights into the genetic architecture of economically important traits in P. hypophthalmus. Nevertheless, further validation in independent populations is required before incorporating these markers into selective breeding programs. Full article

Background/Objectives: Edwardsiella tarda is a rare Gram-negative pathogen that uncommonly infects humans. Neonatal infections are extremely rare but often severe, with a high incidence of central nervous system (CNS) complications. Case presentation: We report a term neonate born via spontaneous vaginal delivery who developed systemic signs of infection within 18 h of life. Blood and cerebrospinal fluid (CSF) cultures grew Edwardsiella tarda. CSF analysis revealed severe meningoencephalitis. Maternal stool culture was also positive for E. tarda, suggesting vertical transmission. Despite initial systemic antibiotic therapy with ampicillin, gentamicin, and ceftriaxone, neuroimaging revealed progressive multifocal brain abscesses. The infant underwent a series of neurosurgical procedures, including bilateral drainage of abscesses, Rickham reservoir placement and ventriculoperitoneal shunting. A revised antibiotic regimen, including systemic meropenem and trimethoprim-sulfamethoxazole plus intrathecal gentamicin, was administered. At six months, the infant showed mild motor delay with lower limb hypertonia and was under close neurosurgical and developmental follow-up. Methods: We conducted a literature review of 12 published neonatal E. tarda infections, including our case. Results: Most infected infants presented within 72 h of life and exhibited CNS involvement. Mortality was 25%, and 44% of survivors experienced long-term neurologic sequelae. Conclusions: Edwardsiella tarda infection in neonates is rare but potentially devastating. Early suspicion, culture confirmation, aggressive antibiotic therapy, and multidisciplinary care, including neurosurgical management, are essential for improving outcomes. Full article

Pseudomonas extremorientalis PEY1, isolated from the intestinal contents of marine fish, was evaluated for the production and properties of antibacterial proteins active against Edwardsiella tarda, a major pathogen in aquaculture. Antibacterial production was maximized in a minimal medium supplemented with 1% yeast extract and 1% galactose under stationary cultivation at 25 °C and pH 7.0. Growth and bioactivity assays were conducted under varying carbon and nitrogen sources, temperatures, and pH levels. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed a distinct ~37 kDa protein band corresponding to antibacterial activity, exhibiting an inhibition zone of 2.4 ± 0.1 cm against E. tarda. The activity was completely abolished by papain digestion but remained detectable after exposure to 55 °C and pH 8, indicating that the active compound is a moderately heat-stable, proteinaceous antibacterial molecule. LC–MS/MS analysis identified the protein as a putative disulfide reductase with ~40% sequence coverage. The antibacterial factor exhibited strong physicochemical stability, retaining activity in the presence of surfactants and metal ions. Collectively, these findings demonstrate that P. extremorientalis PEY1 produces a thermostable, papain-sensitive antibacterial protein with selective activity against E. tarda, highlighting its potential as a promising natural biocontrol or postbiotic candidate for sustainable aquaculture. Full article

This study aims to investigate the differences in microbial community structure between fast-growing (FG) and slow-growing (SG) short-finned eels, Anguilla bicolor pacifica, using high-throughput 16S rDNA sequencing, and to evaluate the potential probiotic properties of Bacillus tropicus isolated from eel intestinal microbiota to enhance growth performance. High-throughput 16S rDNA sequencing revealed no significant differences in the α-diversity between FG and SG eels. Bacterial genera such as Cetobacterium, Clostridium, and Bacteroides were predominant in both groups, with Edwardsiella, Aeromonas, and Fusobacterium being more abundant in SG eels, suggesting a higher presence of potential pathogens. The analysis of the relative abundance of gut microorganisms revealed that SG eels harbored higher levels of potentially pathogenic bacteria, including Edwardsiella tarda and Aeromonas jandaei. In contrast, FG eels exhibited a greater abundance of the potential probiotic B. tropicus. Six strains of bacteria with relative abundance were isolated from the FG group, displaying superior digestive enzyme activity, including protease, lipase, amylase, cellulase, xylanase, and phytase, particularly strain FG2. Phylogenetic analysis confirmed that FG2 was closely related to B. tropicus. A virulence assessment confirmed the non-pathogenic nature of B. tropicus FG2, supporting its probiotic potential. Furthermore, feeding eels a diet supplemented with B. tropicus FG2 significantly enhanced growth performance, as evidenced by increased final weight percentages of weight gain and total production per tank (p < 0.05), while the proximate composition of the dorsal muscle showed an increase in lipid content (p < 0.05). These findings highlight B. tropicus FG2 as a promising probiotic for aquaculture applications. Full article

The aim of this study was to acquire endospore-former(s) for aquatic animal feed based on the probiotic potential in vitro, including the anti-pathogen spectrum, gastrointestinal fluid tolerance, antioxidant activity, enzyme-producing ability, and basic safety assessment. The strain Bacillus velezensis FJAT-57093 was found to exhibit the strongest antibacterial ability against Aeromonas hydrophila in the agar well diffusion inhibition assays from 111 Bacillus-like strains. Moreover, the results showed that the compounds of the strain FJAT-57093 enriched by acid precipitation might be the main antibacterial metabolites. The strain FJAT-57093 also exhibited antibacterial effects against the aquatic pathogens Photobacterium damselae, Edwardsiella tarda, Vibrio parahaemolyticus, and Vibrio vulnificus. The safety assessment revealed that the strain FJAT-57093 was non-hemolytic and susceptible to ten antibiotics. The putative virulence and antibiotic resistance genes predicted were predominantly intrinsic to the FJAT-57093 genome. Furthermore, the strain FJAT-57093 demonstrated a tolerance of acid and bile salt under the simulated gastrointestinal tract conditions, extracellular enzyme-producing abilities, as well as an auto-aggregation rate of 45.88% at 24 h and co-aggregation rates with the aforementioned five aquatic pathogens, ranging from 14.87% to 58.55%. Additionally, its extracellular metabolites displayed strong antioxidant activities, with ABTS⁺ and DPPH radical scavenging rates of up to 99.82% and 42.74%, respectively. In summary, the strain B. velezensis FJAT-57093 was found to possess strong antibacterial activities against multiple aquatic pathogens and desirable in vitro probiotic properties. Full article

The European catfish (Silurus glanis, Linnaeus 1758), commonly known as the wels catfish, is one of the largest freshwater fish in Europe and an ecologically and economically important species in both natural ecosystems and aquaculture. Its broad native distribution, together with the rapid growth of farming practices, increases concerns about pathogen dissemination and their potential impact on biodiversity, animal health, and potential risks to human healthcare. This review is based on a structured literature search following PRISMA recommendations for narrative reviews and summarizes current knowledge on the main pathogen groups affecting S. glanis—viruses (ranaviruses, alloherpesviruses), bacteria (Aeromonas spp., Edwardsiella spp.), protozoan and metazoan parasites (Ichthyophthirius multifiliis, Thaparocleidus spp., Eustrongylides spp., Contracaecum larvae), and oomycetes (Saprolegnia spp., Branchiomyces spp.). Within the One Health approach, particular attention is given to zoonotic pathogens such as Aeromonas spp., Edwardsiella tarda, and helminths like Eustrongylides and Contracaecum, which may cause risks to human health through contaminated water or consumption of raw or undercooked fish. The review integrates findings from field surveys, regional case studies such as those from the Danube basin, and data from the authors’ doctoral research. Because the wels catfish is increasingly cultivated and serves as an apex predator in natural habitats, its effective disease management is critical for both aquaculture and wild populations, and also for the food chains at all. Strengthened surveillance, health monitoring, and biosecurity measures are essential preventing the introduction and spread of pathogens into new hosts and habitats. Through the underlining of major catfish pathogen groups, this review highlights key challenges within the One Health approach and underscores the need for integrated health monitoring, biosecurity, and environmental management strategies. Full article

This study investigated the effects of dietary supplementation with Hylocereus polyrhizus juice by-product extract (HJBE) on growth performance, digestive enzyme activity, antioxidant status, immune response, and disease resistance against Edwardsiella tarda in juvenile Pagrus major. The HJBE, prepared from juice-processing residues, contained measurable levels of bioactive compounds, including vitamin C, total phenolics, and flavonoids, and exhibited noticeable antioxidant activity. Five experimental diets containing 0 (control), 0.5, 1.0, 2.0, and 3.0 g/kg HJBE were fed to juvenile red seabream (initial weight of 7.0 ± 0.01 g) for eight weeks. Fish fed the diet containing 1.0 g/kg HJBE (HJBE1) showed significantly higher final weight, weight gain, specific growth rate, feed efficiency, and protein efficiency ratio compared with other groups. Trypsin activity in intestine was also significantly enhanced in the HJBE1 group, suggesting improved feed utilization. Whole-body composition and hematological indices did not differ among treatments. Plasma antioxidant parameters showed a dose-dependent trend, with catalase and glutathione levels lower at inclusion levels of 0.5–1.0 g/kg. Serum lysozyme activity and immunoglobulin M concentrations were significantly higher in fish fed HJBE1 compared to the controls, corresponding to improved survival after E. tarda challenge. These findings suggest that even moderate levels of bioactive compounds in HJBE can beneficially influence antioxidant homeostasis, immune defense, and growth performance. In conclusion, dietary inclusion of 1.0 g/kg HJBE effectively improved growth, digestive physiology, antioxidant balance, and disease resistance in juvenile P. major. Full article

Background: The extensive use of antibiotics in aquaculture has raised serious concerns, emphasizing the need for sustainable and natural alternatives. This study evaluated the potential of red dragon fruit (Hylocereus polyrhizus) juice by-products (RJB) as a functional feed additive for juvenile red seabream (Pagrus major). Materials and Methods: The bioactive composition and antioxidant capacity of RJB were analyzed, and five experimental diets containing 0, 0.2, 0.4, 0.8, and 1% RJB were fed to fish for 56 days. Results: Growth performance, feed utilization, body composition, antioxidant enzyme activities, and lysozyme activity were evaluated. RJB contained substantial levels of phenolic and flavonoid compounds and exhibited strong radical-scavenging activity. Dietary inclusion of up to 1% RJB did not significantly affect growth, feed efficiency, or plasma biochemistry. However, fish fed the 1% RJB diet showed increased catalase and glutathione levels, significantly enhanced lysozyme activity, and improved survival following Edwardsiella tarda infection. Conclusion: These results demonstrate that RJB can be safely incorporated into marine fish diets to enhance antioxidant capacity and innate immune defense. The valorization of fruit-processing by-products such as RJB offers a promising strategy for developing antibiotic-free and sustainable aquaculture practices. Full article

The Yangtze sturgeon (Acipenser dabryanus) is designated as critically endangered in the IUCN Red List and is a first-class protected species in China. During the summer of 2024, it suffered lethal disease outbreaks. Comprehensive pathological and microbiological analyses were conducted to clarify the etiology. Clinically, infected sturgeon exhibited systemic manifestations including cutaneous ulcers, hemorrhagic septicemia, and diffuse necrosis in liver, kidney and heart tissues. Histopathologically, infected sturgeon showed liver hepatocyte vacuolation/necrosis, renal glomerular atrophy, and cardiac epicardial thickening with lymphocyte/eosinophil infiltration; Gram staining revealed co-localized Gram-positive/negative bacteria in lesions, and TEM identified diverse bacterial morphotypes. Through isolation and molecular identification, four bacterial pathogens were characterized: Streptococcus iniae, Klebsiella pneumoniae, Edwardsiella tarda, and Bacillus cereus. Bacterial load detection revealed the presence of these pathogens in lesion tissues. Antimicrobial susceptibility testing indicated multidrug resistance to florfenicol, tetracycline, and ampicillin (commonly used antibiotics in aquaculture), while high sensitivity to ceftazidime, ceftriaxone, and ciprofloxacin was observed. Thus, we infer that sustained high-temperature stress triggered bacterial co-infection is closely related to this large-scale death incident. This is the first evidence of polymicrobial infection in the Yangtze sturgeon, emphasizing the significance of shifting from a single-pathogen perspective to a multi-pathogen framework, and highlighting the urgency of implementing ecological prevention strategies for this species. Full article