Journal of fish diseases最新文献

von Willebrand factor (vWF) is a large multimeric sialoglycoprotein that plays key roles in normal haemostasis, inflammation regulation, angiogenesis and cancer metastasis in mammals. The gene, protein sequences and functions of vWF in flounder Paralichthys olivaceus (PovWF) were analysed in this study. PovWF possesses an 8550-bp open reading frame (ORF) that encodes a 2849 amino acid protein. PovWF mRNA is highly expressed in the heart and gill, followed by the intestine, skin, spleen, kidney, muscle and liver. PovWF positive cells are mainly endothelial cells (ECs), predominantly located along the inner lining of blood vessels, enclosing the bloodstream. After being infected with hirame novirhabdovirus (HIRRV), flounder exhibits a dark body colour, congested fins and visceral membranes. Histopathologic analysis revealed that the ECs of diseased fish had compromised integrity, accompanied by a significant increase in number of cells within blood vessels. Immunofluorescence and ultrastructural studies showed that virions infect ECs can induce morphological and functional alterations, which lead to the release of vWF and facilitate the migration of neutrophils into tissues to exert antiviral functions. This research pinpoints the role of vWF in the immune response to HIRRV infection in teleost. It offers an in-depth and all-encompassing understanding of the pathophysiological interaction between HIRRV and endothelial cells during invasive infections in fish.

Recirculating Aquaculture Systems (RAS) have been proposed as the future of aquaculture, because they can be used anywhere regardless of access to water, they offer high level of control over farming environment, including biosecurity, and are considered to be sustainable. However, despite of continuous development, there can be still issues with water quality affecting gill health of fish farmed in these systems. This review provides an overview of fish gill structure and gill immune response, and discusses the known impacts of RAS on gill health. Several experimental studies have inadequately reported conditions, particularly water quality, making it difficult to determine if the observed effects were due to water quality issues or RAS system itself. It is crucial for studies investigating the impact of RAS on fish to report water quality during the study. Furthermore, assessments of RAS effects on gill health should include sufficient independent replicates and flow through controls using a common water source. Various methods have been used to assess gill health in RAS, including gill histology, presence of pathogens, gene expression in the gills and gill microbiome analysis. Differences in gill health in fish from RAS and a flow through system have been shown for a number of freshwater and marine fish species. However, these results have been inconsistent across studies, and some results have been challenging to interpret as indicators of gill health. Holistic studies including a number of different methods to assess fish gills would give more conclusive results. More research is needed, in particular, on brackish and marine RAS, to fully understand their impacts on gill health.

Photobacterium damselae subsp. piscicida (Pdp) is characterised by high infectivity and mortality and wide distribution, resulting in substantial economic losses to the global aquaculture industry. Therefore, it is critical to develop a simple, rapid and accurate diagnostic method for Pdp detection. Herein, two Pdp-specific monoclonal antibodies (mAbs 1H7 and 6E6) were obtained, indirect enzyme-linked immunosorbent assay and immunofluorescence analysis confirmed that the mAbs specifically recognised the outer membrane of Pdp but could not recognise the other Gram-positive or Gram-negative bacteria, indicating good specificity. A colloidal gold immunochromatographic strip (CGICS) was developed here for Pdp detection by optimising the colloidal gold labeling and antibody coating conditions using 1H7 as a colloidal gold-labelled antibody and 6E6 as a coated antibody. The CGICS exhibited a detection limit of 1 × 10⁵ CFU/mL for Pdp and a detection time of 10 min. Cross-reaction analysis revealed that the CGICS could specifically detect different Pdp isolates without cross-reaction with the other bacterial species or the subspecies P. damselae subsp. damselae. Stability analysis revealed that the CGICS were stored in closed plastic packaging at 25°C and 4°C for more than 8 months. The CGICS retained their detection limit after 6 months at 4°C, and 4 months at 25°C. Using tissues from the experimentally challenged Lateolabrax maculatus, the CGICS and polymerase chain reaction revealed a 100% coincidence rate. These findings indicated that the established CGICS exhibits high specificity and sensitivity. It is rapid and simple for Pdp detection, making it a potential on-site tool for Pdp detection in fish aquaculture.

Fermentation of Astragalus by Lactobacillus plantarum and Bacillus coagulans can increase the release of active components and degrade its macromolecular substances. This study investigated the effect of fermentation products (Astragalus + L. plantarum + B. coagulans, ALB) on largemouth bass. We specifically focused on growth performance, serum biochemical indices, intestinal microbial diversity, intestinal enzyme activity, immune gene expression and resistance to infections by Aeromonas hydrophila and largemouth bass ranavirus (LMBRaV). The largemouth bass were divided into five groups based on the amount of ALB added to the feed as following, (1) ALB0 (no ALB, ALB0.5 [0.5% addition of ALB], ALB1 [1% addition of ALB], ALB3 [3% addition of ALB], ALB5 [5% addition of ALB]). The feeding trial spanned 28 days. Comprehensively comparing the feeding results of different ALB concentration, the ALB0.5 group showed the best effect. The ALB0.5 group had significantly increased weight gain rate, alkaline phosphatase, total protein, albumin, digestive enzymes activities of lipase, trypsin and increased intestinal villi and thickness of muscularis propria. And it decreased feed conversion ratio, aspartate aminotransferase and alanine aminotransferase of largemouth bass. Furthermore, the ALB0.5 group improved the richness and diversity of the intestinal microbiota. Increased abundance of dominant phylum and genus in the intestine of largemouth bass included Fusobacteria and Cetobacterium, which promoted the growth and immune performance of largemouth bass. After infection with A. hydrophila and LMBRaV, the survival rates were higher in ALB addition experimental groups than in the ALB0 group, respectively. And the survival rate of ALB0.5 group was higher than other groups. Meanwhile, the ALB added to the feed could regulated the immune gene expression (Mx, IRF-3, TNF-α, IL-1β and IL-10), which also promoted the largemouth bass resistance to disease. In summary, adding 0.5% ALB to the diet of largemouth bass can boost its growth performance, immune genes expression, intestinal health and disease resistance.

Rahnella aquatilis as an emerging pathogen can cause bacterial enteritis in cyprinid fish such as crucian carp Carassius auratus. Currently, the characterisation of immune function and gut microbiome composition in C. auratus orally challenged by R. aquatilis were yet unknown. In this study, we therefore investigated the changes of histopathology, white blood cells (i.e., LEU, NEU and LYM), serum biochemical indicators (e.g., CRE, CK and CHO) and digestive enzyme activity (e.g., LYS, AST, ALT, GSH-Px and AKP), as well as complements and immune-related genes (e.g., C3, F2, LysC, TLR3, MyD88, TGF-β, TNF-α and IL-15) that were significantly altered after the oral administration of R. aquatilis KCL-5. Moreover, the gut microbiome composition and diversity were analysed by using 16S rRNA gene high-throughput sequencing analysis. The correlation analysis showed that the high abundance of phylum Proteobacteria, Actinobacteria, Firmicutes and Fusobacteria was related to the pathogenesis of enteritis caused by oral infection. KEGG enrichment analysis indicated that fatty acid, carbon and pyruvate metabolism were significantly increased pathways (p < 0.05). To our best knowledge, this is a rare report of physicochemical properties and gut microbiome in C. auratus by R. aquatilis infection, which will provide a scientific reference for the clinical diagnosis and prevention of bacterial enteritis in cyprinid fish.