Journal of fish diseases最新文献

Koi herpesvirus disease (KHVD), caused by Cyprinid herpesvirus-3 (CyHV-3), poses a significant threat to global aquaculture due to its high mortality rates and economic impact. Current diagnostic methods, such as PCR, are limited by equipment dependency and procedural complexity, hindering point-of-care (POC) applications. To address this, we developed an integrated assay combining recombinase-aided amplification (RAA) with CRISPR-Cas13a-mediated SHERLOCK technology and lateral flow detection (LFD) for rapid and visual detection of CyHV-3 in clinical samples. The KHV-SHERLOCK assay targets a conserved region of the CyHV-3 thymidine kinase (TK) gene, demonstrating exceptional specificity with no cross-reactivity to related pathogens or host DNA. Sensitivity evaluations revealed a detection limit of 100 ag/μL for CyHV-3 plasmid DNA, tenfold more sensitive than the conventional PCR (1 fg/μL) assay, even in the presence of 100 ng of carp genomic DNA as background interference. Clinical validation using 50 archived samples showed 100% concordance with reference PCR results, confirming diagnostic reliability. The assay's isothermal RAA step (37°C, 40 min) and CRISPR-Cas13a detection (37°C, 1 h) enable equipment-free operation, while LFD provides unambiguous visual results within minutes. This platform merges high sensitivity with POC practicality, offering a transformative tool for field-based KHVD surveillance.

Isolating leukocytes from small-bodied fish presents significant technical challenges, especially in species such as grouper, which exhibited rapid blood coagulation. Attaining high purity and quality leukocyte recovery in such species is often hindered by clot formation and erythrocyte contamination. Conventional methods using anticoagulants, buffy coat extraction, and density gradient centrifugation are typically labor-intensive and often yielded inconsistent results. In this study, a streamlined and efficient whole blood lysis protocol for isolating leukocytes from grouper fingerling is described. This protocol offers improvements in blood handling, cell recovery, and cryopreservation. The optimized method significantly reduces processing time, preserves cellular integrity, and facilitates downstream applications in fish immunological studies. Overall, this protocol presented a cost-effective and scalable solution for leukocyte isolation in teleost fish, particularly grouper species.

While nephrocalcinosis (kidney stones) is uncommon in wild teleost fish, various environmental and nutritional factors could lead to its occurrence in aquacultured fish. This study presents the first documented case of kidney stones in aquacultured Brazilian sardine (Sardinella brasiliensis). During necropsy, eighteen hard, white kidney stones were found in the posterior kidney, with an average diameter of 3.71 mm and a total length of 16.8 mm. Morphological analysis revealed stones of different sizes and shapes, including elongated and irregular structures. This discovery enhances our understanding of pathological conditions in S. brasiliensis and underscores the importance of further research into the causes, prevalence and potential implications for fish health and fisheries sustainability.

Myxoid neurothekeoma, also known as nerve sheath myxoma, is a rare benign peripheral nerve sheath tumour primarily reported in mammals, with scarce documentation in teleost fishes. This study reports a confirmed case of myxoid neurothekeoma in the Indian oil sardine (Sardinella longiceps ), a commercially significant marine species along India's southeast coast. An adult female specimen exhibiting a fleshy, dome-shaped, slightly pale brownish mass on the dorsal head was examined grossly and subjected to histopathological analysis using haematoxylin and eosin, Alcian blue and Masson's trichrome staining. Immunohistochemical staining for S100 protein confirmed the neural origin of the tumour cells. Microscopic analysis revealed a well-circumscribed lobular neoplasm composed of spindle to stellate cells within a myxoid stroma rich in acid mucopolysaccharides. Tumour lobules were separated by thin collagenous septa, and widespread S100 positivity supported Schwann cell lineage. The lack of mitotic activity, cytological atypia or invasive features supported a diagnosis of benign myxoid neurothekeoma. This case expands the current understanding of peripheral nerve sheath tumours in marine teleosts and contributes to the broader characterisation of rare neoplasms in aquatic species.

An adult female striped burrfish from a public display aquarium, mixed species recirculating system presented for an exophytic yellow-orange mass on the dorsal head suggestive of neoplasia. The mass was surgically excised twice, adding cryosurgical ablation during the second procedure, but recurred both times post-operatively. After approximately 9 months, euthanasia was elected due to lesion progression. Histopathologic evaluation of surgical biopsy samples and tissues collected at necropsy suggested chromatophoromas. Immunohistochemistry using SOX10, Melan-A and PNL-2 antibodies produced no labelling of tumour cells. Ultrastructurally, neoplastic cells contained poorly formed pterinosomes and vesicles consistent with either xanthophoroma, erythrophoroma or a mixed xanthoerythrophroma. Pigment analysis using absorbance spectrophotometry and gas chromatography mass spectrophotometry identified the primary pigment as xanthopterin with low amounts of the carotenoid tunaxanthin, confirming the diagnosis of xanthophoroma, a rare subtype of chromatophoroma in fish.

Anguillid herpesvirus (AngHV) is a highly pathogenic agent that causes "Mucus sloughing and hemorrhagic septicemia disease" in eels, resulting in high morbidity and cumulative mortality rates. Therefore, accurate diagnosis of AngHV infection is essential for effective clinical management and epidemiological control. In this study, three monoclonal antibodies (mAbs) against AngHV were developed, and their specificity and affinity were validated using Western blotting and indirect immunofluorescence assays. Subsequently, a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was established for the detection of AngHV, employing mAb 10G8-9F4 as the capture antibody and rabbit polyclonal antibody 9NA (which targets AngHV-ORF95) as the detection antibody. Specificity testing indicated no cross-reactivity with other common aquatic viruses, including Koi herpesvirus (KHV), Grass carp reovirus (GCRV), Infectious pancreatic necrosis virus (IPNV), and Large yellow croaker iridovirus (LYCI). The developed assay effectively identified AngHV in various tissues of infected eels, including the heart, liver, spleen, kidney, gills, intestines, muscle, skin mucus, and fins. Compared to quantitative real-time PCR (qPCR), the detection limit of this assay was determined to be 10,000 copies of AngHV, with an 88.89% concordance rate observed in the analysis of clinical samples between the results of DAS-ELISA and qPCR, thereby demonstrating the reliability of this immunoassay for detecting AngHV in field samples. Overall, the DAS-ELISA developed in this study demonstrates high reactivity and specificity, serving as a rapid and effective diagnostic tool for the detection and prevention of AngHV in eel populations.

Nocardia seriolae is the primary cause of fish nocardiosis, and it is urgent to develop an effective vaccine for controlling N. seriolae infection in aquaculture. In our previous study, two potential antigenic proteins, glutamate-cysteine ligase EgtA (EgtA) and hypothetical protein 6747 (hp6747), were determined via the in vivo-induced antigen technique (IVIAT). A DNA vaccine was aimed to be developed using these two in vivo-induced antigens as candidates for ligation with the pcDNA3.1-myc-his-A plasmid, and their immunological effects were evaluated in hybrid snakehead (Channa maculata ♀ × Channa argus ♂). Multiple epitopes of the EgtA and hp6747 proteins from N. seriolae were predicted on both T cells and B cells, and the transcription of the EgtA and hp6747 genes was found in the spleen, trunk kidney, muscle and liver in the fish after immunisation with pcDNA-EgtA and pcDNA-hp6747 DNA vaccines, respectively. Notably, the serum specific antibody (IgM) titres, as well as LYZ, ACP, AKP and SOD activities, were elevated in the vaccinated fish. Meanwhile, quantitative real-time PCR analysis demonstrated that the expression levels of several immune-related genes (TNFα, CD4, CD8α, IL-1β, MHCIIα and MHCIα) were significantly elevated across the aforementioned tissues in the vaccinated fish. Furthermore, they could provide the relative percent survival (RPS) at 61.04% and 43.73% against artificial challenge with N. seriolae in the fish after immunisation with pcDNA-EgtA and pcDNA-hp6747 DNA vaccines, respectively. Taken together, using these two in vivo-induced antigens of EgtA and hp6747 for vaccine development was the ideal strategy for controlling fish nocardiosis in aquaculture.

Lactococcus garvieae, Lactococcus petauri and Lactococcus formosensis are etiological agents of piscine lactococcosis, a disease reported in Italy since the early 1990s and linked to significant aquaculture losses. To the best of our knowledge, this study reports the first detection of L. formosensis subsp. formosensis in farmed rainbow trout (Oncorhynchus mykiss) in Europe. In 2024, a total of 70 trout were sampled in the Piedmont region (Northern Italy), as part of a health monitoring programme. Bacteriological and molecular analyses showed the presence of L. garvieae in four fish (5.7%) and the identification of L. formosensis subsp. formosensis in one single fish exhibiting mild clinical signs via 16S-23S rRNA ITS sequencing. Phylogenetic analysis confirmed the clustering of the isolate within the L. formosensis clade, clearly distinct from L. garvieae and L. petauri. Virulotype comparison showed greater similarity between L. petauri and L. formosensis subsp. formosensis, while the latter exhibited a distinct biochemical profile and was highly susceptible to antibiotics commonly used in aquaculture. Nevertheless, monitoring and advanced diagnostics are essential to clarify the role of this bacterium and to develop any necessary preventive and control measures.

Blood flukes cause serious health issues for farmed bluefin tuna worldwide. Their infection severity has been assessed by counting adult flukes in heart flushes. However, Cardicola orientalis adults reside in blood vessels in the gills. The aim of this study was to assess species composition, prevalence and intensity of adult blood fluke infection in gill blood vessels of ranched Southern Bluefin Tuna, Thunnus maccoyii. Based on molecular analysis, out of 41 adult blood flukes found in the gills of the tuna, 32 flukes were confirmed to be C. forsteri, while only 1 fluke was C. orientalis. There was a significant relationship between the number of adult C. forsteri in the heart and in the gills, with the heart having significantly greater prevalence. The presence of adult C. forsteri in the gills can cause blockage of the gill blood vessels and have a significant effect on the host. Furthermore, the presence of adult C. forsteri in gill blood vessels may have implications for the diagnosis of the infection and in particular identification of a negative host. The presence of adult C. forsteri in gill blood vessels should be recorded in the species description and considered when assessing the effects of this parasite on the host.

In the Norwegian aquaculture industry, opercular shortening has been ranked as an important cause of increased mortality, reduced welfare and growth. The aim of this study was to gather experience-based knowledge from fish health personnel and production staff involved in the commercial production of farmed Atlantic salmon and rainbow trout. A total of 29 semi-structured interviews with a predefined list of questions on the topic of opercular shortening were conducted in the period 22.04.24 to 10.12.24. Results showed that participants reported aggressive behaviour due to underfeeding, with subsequent nipping of gill lids as the main cause of shortened opercula in farmed salmonids. Inadequate feed allocation of fry was perceived to be the most important risk factor for aggression, in addition to starving fry. The prevalence of opercular shortening in the freshwater phase was reported to be between 0% and 70%. Opercular shortening was typically first detected in fry between 2 and 5 g, but sometimes already during first feeding (0.5 g) and in alevins. Damaged gill tissue, reduced growth rates and increased mortality were suggested as consequences of shortened opercula. Sufficient feed allocation in fry stages, optimization of environmental conditions, reducing fish density and culling of small fry were reported as preventive measures, while culling affected fish was the sole mitigating measure.