Diseased Fish Research Articles

A NEW STRATEGIES: ANTIBIOTIC CIRCUMSTANCES FOR RATIONAL DRUG USE AGAINST CLINICAL AEROMONAS HYDROPHILA AND BACTERIAL PROPERTIES OF THIS BACTERIA ON DIFFERENT AGARS

Antibiotic resistance of A. hydrophila was once again observed on different agars. Random antibiotics drug treatment of diseases causes development resistance. Thus, we have faced post-antibiotic era in which our ability to challenge bacteria has diminished and the need for new strategies to deal with disease has increased. A. hydrophila ATCC reference strain, which causes the fatal Motil Aeromonas Septicemia (MAS) Disease in fish, was used in the study Colony structure of A. hydrophila formed on MacConkey (MAC), Aeromonas Isolation Base Agar (AIBA), Congo Red Agar (CRA) and Blood Agar (BA) were examined. The antibiotic susceptibility was determined by using the Kirby-Bauer method Mueller–Hinton Agar, MAC, AIBA and CRA agar plates. A. hydrophila was found sensitive to ciprofloxacin, enrofloxacin, gentamicin, sulphamethoxazole/trimethoprim, and resistant to penicillin G and oxacillin. The important difference was obtained as resistant to enrofloxacin on MAC. Multiple antibiotic resistance index (MARI) of A. hydrophila was determined as 0.33 in MHA and 0.5 in MAC. This difference was due to the antibiotic enroflaxin, and its appearance in this study, where a different new approach was tried for the first time, also added originality to the subject. This status may be related to an acquired plasmid. It is important to try to see resistance of A. hydrophila by using different agars while innovations such as the AntibiogramJ program are being tried to be added to antibiotic literature.

Determination Of Freshwater Consumption Fish Diseases Using Artificial Neural Network Methods

Artificial Neural Network (ANN) is a branch of Artificial Intelligence (AI) that uses neuron-based computational methods to identify and solve problems. In this study, we tried to use ANN to identify diseases of freshwater fish commonly consumed by the public, using one of the ANN methods, namely backpropagation. This research produces a website-based system that uses the backpropagation Neural Network method so that it can be used to help freshwater fish breeders or cultivators identify fish diseases that are kept more accurately than conventional methods. In addition, it is hoped that this system can anticipate more severe infections in fish belonging to cultivators. The results of system testing show that regarding the appearance of the system, 38.5% of respondents answered that the design was beautiful, related to the ease of use of the system, 46.2% of respondents answered that the approach was straightforward to use, regarding the performance of the system 53.8% of respondents answered that the system performance was excellent. Regarding the system's benefits, 76.9% of respondents answered that the system was beneficial

Genome-wide association analysis of the resistance to infectious hematopoietic necrosis virus in two rainbow trout aquaculture lines confirms oligogenic architecture with several moderate effect quantitative trait loci

Infectious hematopoietic necrosis (IHN) is a disease of salmonid fish that is caused by the IHN virus (IHNV), which can cause substantial mortality and economic losses in rainbow trout aquaculture and fisheries enhancement hatchery programs. In a previous study on a commercial rainbow trout breeding line that has undergone selection, we found that genetic resistance to IHNV is controlled by the oligogenic inheritance of several moderate and many small effect quantitative trait loci (QTL). Here we used genome wide association analyses in two different commercial aquaculture lines that were naïve to previous exposure to IHNV to determine whether QTL were shared across lines, and to investigate whether there were major effect loci that were still segregating in the naïve lines. A total of 1,859 and 1,768 offspring from two commercial aquaculture strains were phenotyped for resistance to IHNV and genotyped with the rainbow trout Axiom 57K SNP array. Moderate heritability values (0.15–0.25) were estimated. Two statistical methods were used for genome wide association analyses in the two populations. No major QTL were detected despite the naïve status of the two lines. Further, our analyses confirmed an oligogenic architecture for genetic resistance to IHNV in rainbow trout. Overall, 17 QTL with notable effect (≥1.9% of the additive genetic variance) were detected in at least one of the two rainbow trout lines with at least one of the two statistical methods. Five of those QTL were mapped to overlapping or adjacent chromosomal regions in both lines, suggesting that some loci may be shared across commercial lines. Although some of the loci detected in this GWAS merit further investigation to better understand the biological basis of IHNV disease resistance across populations, the overall genetic architecture of IHNV resistance in the two rainbow trout lines suggests that genomic selection may be a more effective strategy for genetic improvement in this trait.

Identification of TonB-dependent siderophore receptor inhibitors against Flavobacterium columnare using a structure-based high-throughput virtual screening method.

TonB-dependent siderophore receptors play a critical transport role for Flavobacterium columnare virulence formation and growth, and have become valuable targets for the development of novel antimicrobial agents. Traditional Chinese medicine has demonstrated notable efficacy in the treatment of fish diseases and includes potential antibacterial agents. Herein, we performed molecular docking-based virtual screening to discover novel TonB-dependent siderophore receptor inhibitors from traditional Chinese medicine and provide information for developing novel antibacterial agents. Firstly, we efficiently obtained 11 potential inhibitors with desirable drug-like characteristics from thousands of compounds in the TCM library based on virtual screening and property prediction. The antibacterial activity of Enoxolone, along with its interaction characteristics, were determined via an MIC assay and molecular dynamic simulation. Transcriptional profiling, along with validation experiments, subsequently revealed that an insufficient uptake of iron ions by bacteria upon binding to the TonB-dependent siderophore receptors is the antibacterial mechanism of Enoxolone. Finally, Enoxolone's acceptable toxicity was illustrated through immersion experiments. In summary, we have used virtual screening techniques for the first time in the development of antimicrobial agents in aquaculture. Through this process, we have identified Enoxolone as a promising compound targeting the TonB-dependent siderophore receptor of F. columnare. In addition, our findings will provide new ideas for the advancement of innovative antimicrobial medications in aquaculture.

Expanding the Spectrum of Diseases and Disease Associations Caused by Edwardsiella tarda and Related Species

The genus Edwardsiella, previously residing in the family Enterobacteriaceae and now a member of the family Hafniaceae, is currently composed of five species, although the taxonomy of this genus is still unsettled. The genus can primarily be divided into two pathogenic groups: E. tarda strains are responsible for almost all human infections, and two other species (E. ictaluri, E. piscicida) cause diseases in fish. Human infections predominate in subtropical habitats of the world and in specific geospatial regions with gastrointestinal disease, bloodborne infections, and wound infections, the most common clinical presentations in decreasing order. Gastroenteritis can present in many different forms and mimic other intestinal disturbances. Chronic gastroenteritis is not uncommon. Septicemia is primarily found in persons with comorbid conditions including malignancies and liver disease. Mortality rates range from 9% to 28%. Most human infections are linked to one of several risk factors associated with freshwater or marine environments such as seafood consumption. In contrast, edwardsiellosis in fish is caused by two other species, in particular E. ictaluri. Both E. ictaluri and E. piscicida can cause massive outbreaks of disease in aquaculture systems worldwide, including enteric septicemia in channel catfish and tilapia. Collectively, these species are increasingly being recognized as important pathogens in clinical and veterinary medicine. This article highlights and provides a current perspective on the taxonomy, microbiology, epidemiology, and pathogenicity of this increasingly important group.

Implementation of Naïve Bayes Method Diagnosing Diseases Nile Tilapia

The Nile tilapia, also known as Oreochromis niloticus, was a freshwater fish species first produced in East Africa in 1969. It became a popular aquaculture fish in freshwater ponds across Indonesia. Besides its delicious taste, the Nile tilapia is rich in nutrients essential for human health. However, cultivating Nile tilapia was challenging due to frequent bacterial diseases. These diseases often led to mass fish deaths, causing financial losses, especially for new fish farmers. The rapid spread of diseases emphasized the need for prompt intervention to prevent further losses. Farmers needed adequate knowledge about Nile tilapia diseases, but often struggled to absorb information provided by the government. Hence, the presence of experts or veterinarians was crucial in assisting farmers to address these issues. Farmers of Nile tilapia sought assistance from experts or veterinarians, but this was not easy. It involved substantial costs and time, while quick intervention was necessary to mitigate losses. The solution proposed was the development of an expert system for diagnosing and treating Nile tilapia diseases. Thus, an expert system was built to assist fish farmers in identifying fish diseases and their treatments by implementing the naïve Bayes method. The expert system transferred human knowledge to computers, enabling them to solve problems like experts, thereby making expert knowledge accessible to non-experts. Naïve Bayes was implemented to determine the highest probability based on input symptoms. This research used five test data samples to apply the naïve Bayes method to diagnose Nile tilapia diseases, resulting in an accuracy rate of 80%. Therefore, the implementation of naïve Bayes in diagnosing Nile tilapia diseases is considered reasonably effective.

Seasonal Effects on Health Status and Parasitological Traits of an Invasive Minnow in Iberian Waters.

Biological invasions are of special conservation concern in the Iberian Peninsula and other regions with high levels of endemism. Environmental variability, such as the seasonal fluctuations of Mediterranean streams, is a key factor that affects the spread of aquatic species in novel habitats. Fish parasites have a great potential to reflect such changes in the habitat features of freshwater ecosystems. The aim of this study consisted of seasonally analysing the health status and parasitological traits of non-native fish in Iberian waters. In particular, a strongly invasive population of Languedoc minnow Phoxinus septimaniae (leuciscid species native to south-east France) was assessed in Tordera Stream (north-eastern Iberian Peninsula, Mediterranean conditions). Fish were sampled in April, July, and October 2023 by electrofishing. Health status (external/internal organs) was significantly better in autumn (HAI = 28.8) than spring (HAI = 35.6). Life-cycle complexity was higher in spring (LCI = 1.98), whereas parasite abundance and Shannon diversity were significantly lower in autumn (TA = 19.6 and H' = 2.15, respectively). In October (more 'benign' environmental conditions in Iberian streams), minnows could display elevated foraging activity, with fish increasing their health condition and level of parasite resistance/tolerance. Overall results showed a particular seasonal profile of health and parasite infra-communities that allow this minnow species to thrive under highly fluctuating habitat conditions. This information could help environmental managers to control non-native fish in Mediterranean streams.

Isolation, Characterization, and Pathogenicity of an Aeromonas veronii Strain Causing Disease in Rhinogobio ventralis

Rhinogobio ventralis is a rare fish found in the Yangtze River in China and has significant ecological and economic value. In this study, a bacterial strain (RV-JZ01) was isolated from the livers of diseased R. ventralis. This isolate was identified as Aeromonas veronii based on its morphology, biochemical features and 16S rDNA phylogenetic analysis. The artificial infection of healthy R. ventralis (16 ± 2 cm) with RV-JZ01 resulted in the manifestation of clinical symptoms, in accordance with those of naturally infected fish. The 50% lethal dose (LD50) of RV-JZ01 for R. ventralis was 6.3 × 106 CFU/mL. Histopathological examination revealed various pathological changes in the diseased fish, including intestinal villus swelling and rupture, hepatocyte vacuolization, renal tubular cell nuclear enlargement and pyknosis, and myocardial fiber fracture and atrophy. RV-JZ01 infection significantly reduced the gut flora diversity of R. ventralis, with the relative abundances of Firmicutes and Fusobacteria increasing, and those of the Proteobacteria and Bacteroidetes decreasing. The abundance of Lactobacillus and Streptococcus dramatically increased, and the abundance of Clostridium and Escherichia reduced in the intestinal microbiota of R. ventralis infected with RV-JZ01. Antibiotic sensitivity testing revealed that RV-JZ01 was highly susceptible to 12 antimicrobials, including erythromycin, cefalexin, norfloxacin, furazolidone, sulfonamides, enrofloxacin, doxycycline, piperacillin, florfenicol, gentamicin, and lincomycin. These results contribute to the understanding of pathological alterations in R. ventralis following A. veronii infection, offering valuable data to support the implementation of disease treatment.

Virulent and Multi-drug-Resistant Edwardsiella tarda Infection in Oscar Fish: Unveiling the Threat of Mass Mortality and AMR Dissemination.

The Oscar fish (Astronotus ocellatus) is among the most commonly domesticated and exported ornamental fish species from Kerala. The ornamental fish industry faces a significant challenge with the emergence of diseases caused by multi-drug-resistant bacteria. In the present study, six isolates were resolved from the diseased Oscar fish showing haemorrhages, necrosis, and loss of pigmentation. After phenotypic and genotypic characterization, the bacteria were identified as Edwardsiella tarda, Klebsiella pneumoniae, Enterococcus faecalis, Escherichia coli, Brevibacillus borstelensis, and Staphylococcus hominis. Experimental challenge studies in healthy Oscar fish showed that E. tarda caused 100% mortality within 240h with 6.99 × 106CFU/fish as LD50 and histopathology revealed the typical signs of infection. The pathogen was re-recovered from the moribund fish thereby confirming Koch's postulates. E. tarda was confirmed through the positive amplification of tarda-specific gene and virulence genes viz., etfD and escB were also detected using PCR. Antibiotic susceptibility tests using disc diffusion displayed that the pathogen is multi-drug-resistant towards antibiotics belonging to aminoglycosides, tetracyclines, and quinolones categories with a MAR index of 0.32, which implicated the antibiotic pressure in the farm. Plasmid curing studies showed a paradigm shift in the resistance pattern with MAR index of 0.04, highlighting the resistance genes are plasmid-borne except for the chromosome-borne tetracycline resistance gene (tetA). This study is the first of its kind in detecting mass mortality caused by E. tarda in Oscar fish. Vigilant surveillance and strategic actions are crucial for the precise detection of pathogens and AMR in aquaculture.

Blunt snout bream (Megalobrama amblycephala) circARHGEF15 enhances antibacterial immunity against Aeromonas hydrophila infection via ceRNA regulatory axis

Circular RNAs (circRNAs) can be used as therapeutic targets for various human diseases through competitive endogenous RNA (ceRNA). Earlier research in our laboratory has revealed that circRNAs could serve as ceRNA to sponge microRNAs (miRNAs) and regulate the innate immune response of blunt snout bream (Megalobrama amblycephala) after Aeromonas hydrophila infection, but the specific regulation is still uncertain. In this research, by means of overexpression/RNAi, qPCR, and luciferase assay etc., we discovered a circRNA termed circARHGEF15, which was upregulated following A. hydrophila challenge and positively regulated antibacterial immunity in the host. Moreover, we observed that miR-214 can restore the promotion of inflammatory factors due to circARHGEF15 overexpression. Further, our data indicated that circARHGEF15 may function as a ceRNA of miR-214 in the immune reaction generated by A. hydrophila, reduce the inhibition of miR-214 on hepcidin, and promote the expression of downstream proinflammatory factors such as il-1β, il-6, il-8, and tnf-α. In summary, the results of this study suggest that M. amblycephala circARHGEF15 acts a significant function in the modulation of antibacterial response to A. hydrophila infection, and lays the foundation for rapid diagnosis, effective control, and treatment of fish diseases from the perspective of circRNAs in the future.

Pathogen identification and epidemic factor analysis of yellow catfish, Pelteobagrus fulvidraco, red lower jaw disease

Since 2020, another type of epidemic disease, ‘red lower jaw disease’ (RLJD), has broken out in yellow catfish Pelteobagrus fulvidraco every spring in China, causing large-scale deaths and significant economic losses. This new disease has the characteristics of strong infectivity, high mortality and a single host. To prevent and control RLJD, epidemiological investigation, transmission electron microscopy (TEM), virome sequencing, Koch's rule verification and epidemic factor investigation were studied in this article. The clinical symptoms of diseased yellow catfish were pale gill filaments, hyperaemia and swelling of the spleen and kidney. TEM results revealed that a large number of 35–40 nm spherical virus particles without envelope structure were found in the cytoplasm of spleen cells. The liver, spleen and kidney of the diseased fish had serious lesions. After virome sequencing, the calicivirus reads in the unique virus reads accounted for 99.5% of the unique virus reads in the diseased fish, which provided a relevant reference value for identifying the pathogen of RLJD. The full-length sequence of yellow catfish calicivirus (YCCV) obtained at 7405 bp, including the RNA-helicase domain, RdRp-1 domain and d1iqqa domain. At the same time, both PCR and TaqMan fluorescence quantitative PCR detection method of YCCV were established. Through the artificial infection test, YCCV was verified as the pathogen for RLJD. It was also found that YCCV mainly harmed the fish within 1 year, whereas the fish above 2 years had good resistance. The water temperature of the RLJD outbreak was mainly concentrated at 18 °C–24 °C. In the current study, after YCCV was verified as the pathogen of RLJD, epidemic factors including fish age and water temperature were studied, to the best of our knowledge, for the first time to provide a relevant theoretical basis for the pathogenic mechanism and prevention and control measures of yellow catfish RLJD.

Exploring the underlying mechanisms of enteritis impact on golden pompano (Trachinotus ovatus) through multi-omics analysis

Enteritis posed a significant health challenge to golden pompano (Trachinotus ovatus) populations. In this research, a comprehensive multi-omics strategy was implemented to elucidate the pathogenesis of enteritis by comparing both healthy and affected golden pompano. Histologically, enteritis was characterized by villi adhesion and increased clustering after inflammation. Analysis of the intestinal microbiota revealed a significant increase (P < 0.05) in the abundance of specific bacterial strains, including Photobacterium and Salinivibrio, in diseased fish compared to the healthy group. Metabolomic analysis identified 5479 altered metabolites, with significant impacts on terpenoid and polyketide metabolism, as well as lipid metabolism (P < 0.05). Additionally, the concentrations of several compounds such as calcitetrol, vitamin D2, arachidonic acid, and linoleic acid were significantly reduced in the intestines of diseased fish post-enteritis (P < 0.05), with the detection of harmful substances such as Efonidipine. In transcriptomic profiling, enteritis induced 68 upregulated and 73 downregulated genes, predominantly affecting steroid hormone receptor activity (P < 0.05). KEGG pathway enrichment analysis highlighted upregulation of SQLE and CYP51 in steroidogenesis, while the HSV-1 associated MHC1 gene exhibited significant downregulation. Integration of multi-omics results suggested a potential pathogenic mechanism: enteritis may have resulted from concurrent infection of harmful bacteria, specifically Photobacterium and Salinivibrio, along with HSV-1. Efonidipine production within the intestinal tract may have blocked certain calcium ion channels, leading to downregulation of MHC1 gene expression and reduced extracellular immune recognition. Upregulation of SQLE and CYP51 genes stimulated steroid hormone synthesis within cells, which, upon binding to G protein-coupled receptors, influenced calcium ion transport, inhibited immune activation reactions, and further reduced intracellular synthesis of anti-inflammatory substances like arachidonic acid. Ultimately, this cascade led to inflammation progression, weakened intestinal peristalsis, and villi adhesion. This study utilized multi-level omics detection to investigate the pathological symptoms of enteritis and proposed a plausible pathogenic mechanism, providing innovative insights into enteritis verification and treatment in offshore cage culture of golden pompano.

Database construction and comparative genomics analysis of genes involved in nutritional metabolic diseases in fish

Nutritional metabolic diseases in fish frequently arise in the setting of intensive aquaculture. The etiology and pathogenesis of these conditions involve energy metabolic disorders influenced by both internal genetic factors and external environmental conditions. The exploration of genes associated with nutritional and metabolic disorder has sparked considerable interest within both the aquaculture scientific community and the industry. High-throughput sequencing technology offers researchers extensive genetic information. Effectively mining, analyzing, and securely storing this data is crucial, especially for advancing disease prevention and treatment strategies. Presently, the exploration and application of gene databases concerning nutritional and metabolic disorders in fish are at a nascent stag. Therefore, this study focused on the model organism zebrafish and five primary economic fish species as the subjects of investigation. Using information from KEGG, OMIM, and existing literature, a novel gene database associated with nutritional metabolic diseases in fish was meticulously constructed. This database encompassed 4583 genes for Danio rerio, 6287 for Cyprinus carpio, 3289 for Takifugu rubripes, 3548 for Larimichthys crocea, 3816 for Oreochromis niloticus, and 5708 for Oncorhynchus mykiss. Through a comparative systems biology approach, we discerned a relatively high conservation of genes linked to nutritional metabolic diseases across these fish species, with over 54.9 % of genes being conserved throughout all six species. Additionally, the analysis pinpointed the existence of 13 species-specific genes within the genomes of large yellow croaker, tilapia, and rainbow trout. These genes exhibit the potential to serve as novel candidate targets for addressing nutritional metabolic diseases.

Potential plasma biomarkers for the onset of heart and skeletal muscle inflammation from Piscine orthoreovirus-1 infection in Atlantic salmon (Salmo salar)

Biomarkers that give quantifiable information about disease development are valuable diagnostic indicators providing opportunities to thwart adverse outcomes through timely detection and initiation of countermeasures. Whereas human medicine already relies extensively on biomarker analysis, their application in the diagnostics of fish diseases is still at a tentative beginning. However, the increased utilisation of broad-range analytical approaches such as untargeted proteomics enhances the chances to discover changes in the levels of proteins, which are connected to fish health and could serve as novel biomarkers. In the present study, proteomic analysis accompanied by biostatistical data processing was employed with the aim of identifying plasma biomarker candidates for the onset of heart and skeletal muscle inflammation (HSMI) caused by Piscine orthoreovirus (PRV)-1 infection in Atlantic salmon. HSMI is a common viral disease and threat to fish welfare and productivity in Norwegian aquaculture, so that the early detection of HSMI development would allow a timely intervention to limit the damage. In the search for biomarker candidates, salmon plasma was sampled five and eight weeks after a PRV-1 cohabitation challenge experiment and from adequate control fish, and analysed by mass spectrometry-based proteomics. The proteome dataset contained 695 proteins with >90% probability of correct identification according to the set cut-off criteria for peptide quality. Time- and condition-related differences in protein abundance levels were revealed by multivariate analysis. Comparison of the proteins identified as significant using three different biostatistical models resulted in a short list of four potential biomarkers: galectin-3-binding protein (Gal-3BP), fucolectin-6, urokinase plasminogen activator surface receptor and ryanodine receptor 3. The physiological functions described for these proteins in mammals designate them as interesting indicators of inflammatory diseases also in other species, such as PRV-1 pathogenesis in salmon. In situ-hybridisation targeting Gal-3BP and PRV-1 mRNA in heart tissue sections from the same challenge trial showed a significant upregulation of Gal-3BP mRNA in infected salmon hearts as compared to controls, supporting the findings of the proteomic analysis and suggesting a role in the onset of heart- and skeletal muscle inflammation.

A Duplex PCR Assay for Rapid Detection of Klebsiella pneumoniae and Chryseobacterium in Large Yellow Croaker Fish.

Both Klebsiella pneumoniae and Chryseobacterium cause an increasing number of diseases in fish, resulting in great economic losses in aquaculture. In addition, the disease infected with Klebsiella pneumoniae or Chryseobacterium exhibited the similar clinical symptoms in aquatic animals. However, there is no effective means for the simultaneous detection of co-infection and discrimination them for these two pathogens. Here, we developed a duplex polymerase chain reaction (PCR) method based on the outer membrane protein A (ompA) gene of Klebsiella pneumoniae and Chryseobacterium. The specificity and validity of the designed primers were confirmed experimentally using simplex PCR. The expected amplicons for Klebsiella pneumoniae and Chryseobacterium had a size of 663 and 1404 bp, respectively. The optimal condition for duplex PCR were determined to encompass a primer concentration of 0.5 μM and annealing temperature of 57°C. This method was analytical specific with no amplification being observed from the genomic DNA of Escherichia coli, Vibrio harveyi, Pseudomonas plecoglossicida, Aeromonas hydrophila and Acinetobacter johnsonii. The limit of detection was estimated to be 20 fg of genomic DNA for Chryseobacterium and 200 fg for Klebsiella pneumoniae, or 100 colony-forming units (CFU) of bacterial cells in both cases. The duplex PCR was capable of simultaneously amplifying target fragments from genomic DNA extracted from the bacteria and fish liver. For practical validation of the method, 20 diseased fish were collected from farms, among which 4 samples were PCR-positive for Klebsiella pneumoniae and Chryseobacterium. The duplex PCR method developed here is time-saving, specific, convenient, and may prove to be an invaluable tool for molecular detection and epidemiological investigation of Klebsiella pneumoniae and Chryseobacterium in the field of aquaculture.

High-intensity exercise training in large yellow croaker is a compromise between disease resistance and fish welfare

Exercise training is being applied to improving the productivity and welfare of farmed fish species. Nonetheless, research into whether exercise training improves disease resistance and immune function in fish is still at an early stage, and more studies is required. This study examined the impact of exercise training on growth performance, disease resistance and immune function of large yellow croaker (Larimichthys crocea). Juvenile fish underwent a 12 days training regime at 2–3 BL.s−1, followed by a parasite disease challenge test (Cryptocaryon irritans). Fish muscle RNA-seq analyses was used to evaluate the influence of exercise on juvenile immune function. The results showed that: (1) exercising at 2–3 BL.s−1 had no impact on the growth of juvenile croakers, however it induced an inflammatory response in croakers, leading to increased mortality in the treatment group (T) compared to the control group (C); (2) exercising also enhanced the resistance of T to C. irritans, resulting in a significant 17.6% increase in the survival rate of T compared to that of C; and (3) the RNA-seq analysis of the muscles demonstrated that differentially expressed genes (DEGs) between T and C were primarily involved in regulating the expression of genes related to muscle development and immunity in croaker; (4) enrichment analyses using KEGG and GO revealed that the DEGs were significantly enriched in pathways related to metabolic processes and biosynthesis. In conclusion, it is suggested that exercise training with high water speed induces an inflammatory response in the large yellow croaker, compromising the welfare of the fish. However, this stimulates the expression of immune-regulation-related genes and pathways, thereby improving the disease resistance of exercising individuals. Our study reveals that exercise training can improve disease resistance of large yellow croaker, which has significant implications for the sustainability of the croaker aquaculture industry.

An aquaculture risk model to understand the causes and consequences of Atlantic Salmon mass mortality events: A review

AbstractMass mortality events (MMEs) are defined as the death of large numbers of fish over a short period of time. These events can result in catastrophic losses to the Atlantic salmon aquaculture industry and the local economy. However, they are challenging to understand because of their relative infrequency and the high number of potential factors involved. As a result, the causes and consequences of MMEs in Atlantic salmon aquaculture are not well understood. In this study, we developed a structural network of causal risk factors for MMEs for aquaculture and the communities that depend on Atlantic salmon aquaculture. Using the Interpretive Structural Modeling (ISM) technique, we analysed the causes of Atlantic salmon mass mortalities due to environmental (abiotic), biological (biotic) and nutritional risk factors. The consequences of MMEs were also assessed for the occupational health and safety of aquaculture workers and their implications for the livelihoods of local communities. This structural network deepens our understanding of MMEs and points to management actions and interventions that can help mitigate mass mortalities. MMEs are typically not the result of a single risk factor but are caused by the systematic interaction of risk factors related to the environment, fish diseases, feeding/nutrition and cage‐site management. Results also indicate that considerations of health and safety risk, through pre‐ and post‐event risk assessments, may help to minimize workplace injuries and eliminate potential risks of human fatalities. Company and government‐assisted socio‐economic measures could help mitigate post‐mass mortality impacts. Appropriate and timely management actions may help reduce MMEs at Atlantic salmon cage sites and minimize the physical and social vulnerabilities of workers and local communities.

Not that many leech species after all: Myzobdella lugubris and Myzobdella patzcuarensis (Annelida: Hirudinida) are the same species

The genus Myzobdella groups five species of leeches parasites of fishes mainly of freshwater but with tolerance to brackish waters. Native distribution of these species includes the New World from North to South America. Myzobdella lugubris Leidy, 1851, the type species of the genus, was briefly described based on specimens from the USA, but subsequently their morphology, known distribution and host range were expanded; however, less is known about the other four species of the genus. As part of a survey focusing on characterizing the diversity of leeches from Mexico, specimens of Myzobdella patzcuarensis (Caballero, 1940), from the type locality of the species were included for the first time in a phylogenetic study. In addition, specimens assigned to Myzobdella from the southeast of Mexico as well as from Nicaragua, were also included. In the resulting phylogenetic tree, our newly generated sequences were found nested in the same clade that M. lugubris; with unresolved relationships and relatively low genetic divergence, suggesting conspecificity. In addition, the internal morphology of the specimens of Myzobdella from Mexico is consistent with the description of M. lugubris. Our morphological examination reveals high degrees of variability in the external pigmentation of the specimens. Based on our results we formally synonymize M. patzcuarensis under M. lugubris.

Recent advances of Terminalia catappa and its application in fish culture: A review

AbstractHigh‐intensity aquaculture may cause the aquatic animals to experience elevated stress levels, which in turn will increase their susceptibility to illness and result in substantial losses. Farmers frequently use chemical and antibiotic treatments for fish diseases, which have led to drug‐resistant and hazardous residues in farmed fish and the environment. Consequently, finding substitutes for chemicals and antibiotics is crucial for disease management in aquaculture. Terminalia catappa L. or commonly called Indian almond is well known for its medicinal properties and widely distributed in tropical and subtropical regions. T. catappa contains chemical compounds such as tannin and flavonoid that play an important role in antibacterial, anti‐allergy, anti‐inflammation, and anti‐cancer. Numerous studies have been conducted on leaves, bark, fruits, and seed of T. catappa for their applications, including medicinal, bioremediation (dye absorption), and aquaculture use. Much research can be found on the utilization of T. catappa leaves to improve fish well‐being, mostly in the ornamental fish industry. Extract of T. catappa has been found to improve fish survival, growth rate, inhibit bacterial infection, improve water quality, enhance fish colouration, and boost the immune response. Although T. catappa leaves have undergone substantial research, it has not been systematically described in connection to fish species used in aquaculture. This review will systematically discuss the biotoxicity of T. catappa evaluation of growth‐promoting properties, eggs and larviculture performance, and enhancement of fish resistance to various bacteria, fungi, and parasites. In addition, the article also highlights the future perspectives of using T. catappa to improve fish culture.

Intestinal microbiota and gene expression alterations in leopard coral grouper (Plectropomus leopardus) under enteritis

Enteritis poses a significant threat to fish farming, characterized by symptoms of intestinal and hepatic inflammation, physiological dysfunction, and dysbiosis. Focused on the leopard coral grouper (Plectropomus leopardus) with an enteritis outbreak on a South China Sea farm, our prior scrutiny did not find any abnormalities in feeding or conventional water quality factors, nor were any specific pathogen infections related to enteritis identified. This study further elucidates their intestinal flora alterations, host responses, and their interactions to uncover the underlying pathogenetic mechanisms and facilitate effective prevention and management strategies. Enteritis-affected fish exhibited substantial differences in intestinal flora compared to control fish (P = 0.001). Notably, norank_f_Alcaligenaceae, which has a negative impact on fish health, predominated in enteritis-affected fish (91.76 %), while the probiotic genus Lactococcus dominated in controls (93.90 %). Additionally, certain genera with pathogenesis potentials like Achromobacter, Sphingomonas, and Streptococcus were more abundant in diseased fish, whereas Enterococcus and Clostridium_sensu_stricto with probiotic potentials were enriched in control fish. At the transcriptomic level, strong inflammatory responses, accompanied by impaired metabolic functions, tissue damage, and iron death signaling activation were observed in the intestines and liver during enteritis. Furthermore, correlation analysis highlighted that potential pathogen groups were positively associated with inflammation and tissue damage genes while presenting negatively correlated with metabolic function-related genes. In conclusion, dysbiosis in the intestinal microbiome, particularly an aberrantly high abundance of Alcaligenaceae with pathogenic potential may be the main trigger for this enteritis outbreak. Alcaligenaceae alongside Achromobacter, Sphingomonas, and Streptococcus emerged as biomarkers for enteritis, whereas some species of Lactococcus, Clostridium_sensu_stricto, and Enterococcus showed promise as probiotics to alleviate enteritis symptoms. These findings enhance our understanding of enteritis pathogenesis, highlight intestinal microbiota shifts in leopard coral grouper, and propose biomarkers for monitoring, probiotic selection, and enteritis management.