Journal of fish diseases最新文献

This study presents the first case in Poland of isolation and molecular identification of the Spironucleus vortens parasite from the digestive tract of diseased ornamental fish belonging to the species discus fish (Symphysodon discus Heckel, 1840). Recently, an increasing percentage of fish submitted for testing to the Department of Biology and Fish Diseases, have been observed that show typical symptoms of hole-in-the-head disease, therefore it is important to have accurate information about this disease. In preparation of this work, two fish were studied. The polymerase chain reaction (PCR) used a pair of primers designed specifically for this experiment. The amplification product was sequenced and the partial sequence of small ribosomal subunit (18S rRNA) was deposited in the GenBank database. The obtained nucleotide sequence showed a high percentage of identity with the compared sequence of the S. vortens reference strain (98.52%). Additionally, the presence of potentially dangerous bacteria belonging to four species, namely Citrobacter braakii, Acinetobacter lwoffi, Pseudomonas putida and Comamonas testosteroni was confirmed in the material collected from the tested fish. Bacterial isolates were examined biochemically. An antibiotic susceptibility testing showed that in three of the four isolates there appeared resistance to the drugs used. Trial Registration: Clinical trial registration was not required for this study.

Melanisation can occur in the musculature of fish. A well-known form is the melanised focal changes, or 'black spots', in the fillet of farmed Atlantic salmon (Salmo salar). The aetiology of black spots has not been fully determined, though recent research has emphasised the role of fat necrosis in their development. The initial stages of the changes are observed as focal haemorrhages or 'red spots', and these can progress into melanised focal changes (MFCs). The focal haemorrhages are acute changes characterised by necrotic myocytes and adipocytes and diffuse haemorrhage in the tissue. These changes evolve into a chronic inflammation dominated by fibrosis, encapsulated lipid droplets or pseudocysts, presence of epithelioid cells, granulomas of varying character, giant cells and melano-macrophages, whose presence accounts for the discolouration. The inflammation ranges from mild to severe, and the severity of the lesion has been associated with localised piscine orthoreovirus 1 (PRV 1) replication in macrophages and melano-macrophages within granulomas. The possibility of a genetic impact on the condition has not been supported by available data. The lipid composition and the antioxidative properties of the feed have been shown to affect the development of the changes. Physiological and environmental factors are also believed to influence the prevalence and severity of the condition. Here, we review the current state of knowledge concerning melanisation in fish skeletal musculature, with a special emphasis on the MFCs in Atlantic salmon.

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.

Nodular gill disease (NGD) is a serious proliferative gill condition that affects farmed salmonids, particularly in Europe. While the cause of NGD remains unknown (and maybe multifactorial), various amoebae are often isolated from the gills of affected fish and can in some cases be seen associated with lesions by histopathology. The present study aimed to quantify the abundance of different amoeba species directly from the gills of rainbow trout affected by NGD and healthy controls. An 18S rRNA amplicon metagenomic approach was employed to profile the diversity and abundance of micro-eukaryotes (including amoebae) while suppressing the amplification of host DNA using a salmonid-specific C3 spacer blocking primer. The 18S rRNA metagenomics approach identified a diversity of micro-eukaryotes on the gills of rainbow trout, including the phylum's Amoebozoa, Diatomea, Platyhelminthes and Ciliophora. Rainbow trout clinically affected by NGD had a significantly higher abundance of a specific sequence (zOTU2) classified as Vannella sp. compared to healthy controls. A quantitative PCR assay was then developed and validated which accurately quantified the abundance of this Vannella sp. sequence from a NGD outbreak in a Swiss rainbow trout farm. Additional PCR and Sanger sequencing analysis of the zOTU2 sequence demonstrated that this sequence is most likely derived from Vannella mustalahtiana. Our study highlights the potential role of Vannella mustalahtiana in NGD in Switzerland and further describes a specific and validated diagnostic PCR assay for accurate detection of this Vannella species.

White spot syndrome virus (WSSV) and Enterocytozoon hepatopenaei (EHP) represent the most economically destructive pathogens in the current shrimp industry. WSSV causes white spot disease (WSD) responsible for rapid shrimp mortality, while EHP stunts growth and therefore reduces overall productivity. Despite the importance of timely disease detection, current diagnostic methods for WSSV and EHP are typically singleplex, and those offering multiplex detection face issues such as complexity, low field compatibility and/or low sensitivity. Here, we introduce an orthogonal, multiplex CRISPR-Cas assay for concomitant detection of WSSV and EHP. This method combines recombinase polymerase amplification (RPA) for target DNA enrichment with Cas12a and Cas13a enzymes for fluorescent detection. This assay produces distinct fluorescent colours for different diagnostic outcomes, allowing naked eye visualisation without ambiguity. Further validation reveals that the assay detects as few as 20 and 200 copies of target DNA from EHP and WSSV, respectively, while producing no false positives with DNA from other shrimp pathogens. Moreover, the assay excellently agrees with established PCR methods in evaluation of clinical samples. Requiring only 37°C and less than an hour to complete, multiplex CRISPR-Cas assay presents a promising tool for onsite diagnostics, offering high accuracy while saving time and resources.

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.