Journal of fish diseases最新文献

Mariculture, a significant component of the maritime industry that focuses on marine food production, faces challenges in maintaining productivity during bacterial disease outbreaks, particularly in high-value aquaculture such as the four-finger threadfin fish in Taiwan. Streptococcosis, caused by Streptococcus iniae, is a major contributor to the mortality of the four-finger threadfin (Eleutheronema tetradactylum). Recurrent streptococcosis outbreaks have highlighted the pressing need for highly effective vaccination strategies. Given its safety, environmental friendliness, and protective effects, vaccination is widely acknowledged as an effective means of preventing aquatic diseases. An innovative approach involves using biofilm-forming S. iniae as vaccine candidates for aquaculture. This study presents an effective approach for developing a biofilm-based vaccine by cultivating S. iniae on chitosan particles, facilitating robust biofilm formation and enhancing immune responses in four-finger threadfin fish. For comparison, a formalin-killed cell (FKC) vaccine, prepared from whole-cell S. iniae, was evaluated. Immune responses were examined in the blood, mucus, and gut lavage from both the vaccinated and control groups. These responses include immune-related gene expression, antibody titers, and lysozyme activity. At 30 days post-vaccination, the biofilm vaccine group exhibited elevated antibody titers, with values of 0.23 ± 0.02 in serum, 0.09 ± 0.01 in mucus, and 0.16 ± 0.01 in gut lavage. Following vaccination, both the FKC and biofilm vaccines significantly upregulated the expression of key proinflammatory cytokines (tumour necrosis factor-α, interleukin [IL]-10, IL-12) in the spleen and kidney, indicating robust activation of the innate immune response. However, the biofilm vaccine induced markedly higher expression of these cytokines, highlighting its stronger stimulation of innate immune responses. These results suggest that the biofilm-based formulation stimulates early immune signalling pathways that are critical for protection against S. iniae infection. In the challenge experiments, the relative percent survival was of 22.85% for the biofilm and 42.8% for the FKC vaccine groups. This study demonstrates that while both FKC and biofilm vaccines activated innate and adaptive immunity, the FKC vaccine provided higher protection (RPS 42.8% vs. 22.85%), indicating that strong immunogenicity does not always translate into effective protection and that oral vaccine strategies require further refinement. Further optimisation of oral vaccine formulations is required to improve the protective efficacy of biofilm-based vaccines 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.

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.

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.

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.

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.

Goldfish (Carassius auratus) are among the most widely cultured ornamental fish. Skeletal deformities and muscular lesions have been reported in cyprinids, but their aetiology and pathology remain unclear. Advanced diagnostic tools, including radiography, ultrasonography and computed tomography, provide valuable insights when combined with histopathology. This study aimed to characterise clinical, radiological, ultrasonographical, computed tomographical and histopathological features of goldfish with hump-like lesions and muscular cavities caused by Myxobolus lentisuturalis in two farms, and to compare disease manifestations between populations using advanced imaging plus histology. From January 2023 to March 2024, ~10% of fish from two commercial goldfish farms in Tehran Province showed clinical signs. The first group had only hump-like lesions behind the head without exudate, whereas the second also had large muscular cavities with whitish exudate. Thirty goldfish (15 per farm) were sampled. Digital radiography, B-mode ultrasonography, computed tomography (CT/3D-CT), wet smears and histopathological sections were prepared. In the first stock, bilateral crescent-shaped humps containing Myxobolus lentisuturalis spores were observed, with radiographs revealing increased lesion density and obscured swim bladder margins, and ultrasonography indicating muscular hypertrophy with elevated echogenicity. In the second stock, hump-like lesions accompanied by exudates, cavitations, and severe muscular dystrophy were detected, supported by radiographic and CT evidence of deformity, cavitation, and asymmetry. This study demonstrated that M. lentisuturalis infection in goldfish can present with distinct clinical and pathological manifestations, ranging from localised hump-like lesions to extensive muscular cavitation and deformity. The integration of radiography, ultrasonography, CT imaging, and histopathology provided a comprehensive diagnostic approach for characterising disease progression. These findings highlight the importance of advanced imaging modalities in ornamental fish medicine and contribute to a better understanding of myxozoan-associated lesions in cyprinids.

Adult salmon enteritis (ASE), characterised by severe ulcerative enteritis, has been linked to prespawn mortality (PSM) in spring Chinook salmon (Oncorhynchus tshawytscha) in certain rivers in Oregon, USA. Catastrophic losses of spring Chinook salmon have resulted from PSM, a significant threat to their population stability. Understanding the causes of ASE is therefore critical for mitigating PSM and supporting conservation. This study investigates the potential infectious aetiology of ASE using a juvenile Chinook salmon model. Fish were immunocompromised with dexamethasone implants, fasted, and exposed to intestinal tissues from ASE-affected adult Chinook. Histopathology of recipient fish revealed mid-intestinal lesions consistent with ASE. The microsporidium Enterocytozoon schreckii, which is observed in ASE-affected adults from rivers, was transmitted for the first time to juvenile Chinook Salmon, making E. schreckii a potential new pathogen of juvenile salmon. Additionally, intranuclear inclusions were identified in enterocytes by histopathology and viral particles were detected by electron microscopy in recipient fish. The study demonstrates that intestinal lesions consistent with ASE can be experimentally induced in juvenile Chinook salmon through oral exposure to infected tissues, supporting an infectious aetiology. Further research is needed to isolate specific pathogens, including viruses and E. schreckii, and to elucidate their roles in ASE development.

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.

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.