Journal of fish diseases最新文献

The gill parasite Sparicotyle chrysophrii poses a significant threat to gilthead sea bream (Sparus aurata) aquaculture in the Mediterranean, causing considerable mortality and economic losses. As traditional chemotherapeutic treatments, like formalin, face growing regulatory restrictions, there is an urgent need for alternative control strategies. This study screened the in vitro antiparasitic activity of 16 phytogenic active ingredients (AIs), including essential oils (EOs) and commercial feed additives, against adult S. chrysophrii. Worms were exposed to a range of concentrations of each compound, and mortality was assessed over 24 h. Lethal dose 50% (LD₅₀) values were calculated and categorised by short-, mid-, and long-term efficacy. Several AIs, such as Cinnamomum zeylanicum, Origanum vulgare, Thymus vulgaris, and the commercial formulations Arotec-G and OA + HE+EO, demonstrated rapid and strong toxicity, with low LD₅₀ values observed within 2 h. In addition to lethality, characteristic morphological damage was detected in exposed parasites, indicating a direct and severe parasiticidal effect. These results highlight the high efficacy of various AIs at concentrations significantly lower than those used in standard formalin baths. Overall, the study identifies several promising candidates for the development of alternative treatments against S. chrysophrii, providing a solid scientific basis for future in vivo validation and integration into sustainable parasite control programs in marine aquaculture.

Turbot (Scophthalmus maximus ) is an economically important farming fish in China. Turbot circovirus (TCV), a recently discovered member of the Circovirus genus within the Circoviridae family, has emerged as a significant threat to the turbot aquaculture industry in China. This virus is the causative agent of turbot acute hemorrhagic disease (TAHD), resulting in substantial economic losses in recent years. As a novel pathogen, the development of more accurate and efficient detection methods for TCV remains an urgent need. In this study, the specific probe and primers were designed based on the consensus sequence of the cap gene of TCV to develop a TaqMan probe-based real-time PCR method for virus detection. The specificity of the assay was validated using turbot reddish body iridovirus (TRBIV), viral nervous necrosis virus (VNNV), the cap gene of European catfish (Silurus glanis ) circovirus (CfCV) and European eel (Anguilla anguilla ) circovirus (EeCV), and no cross-reaction was observed, indicating the high specificity of the established method. The detection limit of this assay was 10¹ copies per reaction, with an efficiency of 93.7%, a regression squared value of 0.999, and a linear range from 10¹ copies to 10⁸ copies of TCV DNA. The assay demonstrated high specificity, sensitivity and reproducibility, with both intra- and inter-assay coefficients of variation less than 2.0%. Then 390 clinical samples suspected of TAHD collected from 2019 to 2022 were tested using this method, and all the samples tested positive for TCV. In this study, we established a TaqMan qPCR-based method for TCV detection, which could be applied to epidemiological investigations and pathogenic studies of TCV.

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.

Grass carp (Ctenopharyngodon idellus) is a vital species in China's aquaculture industry but is highly susceptible to grass carp haemorrhagic disease (GCHD) caused by the grass carp reovirus (GCRV). GCRV infection in Ctenopharyngodon idellus kidney cells (CIK) induces reactive oxygen species (ROS) overproduction, triggering oxidative stress. Catalase (Cat) is a crucial antioxidant enzyme that decomposes hydrogen peroxide (H₂O₂) into H₂O and O₂. In this study, we investigated and characterised the roles of CiCat in grass carp. CiCat is expressed ubiquitously in all examined tissues. Furthermore, when challenged with GCRV, its expression levels are significantly upregulated. Fluorescence analysis revealed that CiCat exhibits a widespread cellular distribution, while GCRV infection enhances its aggregation and co-localisation with mitochondria (Mit) and endoplasmic reticulum (ER). Overexpression of CiCat eliminates both H₂O₂ and GCRV-induced ROS, decreases the expression of antioxidant enzymes and promotes GCRV replication. Further research showed that overexpression of interferon regulatory factor-7 (IRF-7) inhibits GCRV replication, but CiCat reduces IRF-7 expression. In summary, CiCat promotes GCRV replication by reducing CiIRF-7 expression.

Cestode infestations in cultured fish have resulted in significant economic problems associated with international trade. Pharmacological treatments containing albendazole (ABZ) represent a promising alternative for controlling these infestations. This study evaluated the in vitro efficacy of ABZ against the metacestode Parvitaenia cochlearii, a parasite of the Pacific fat sleeper (Dormitator latifrons), by exposing the parasites to different concentrations (200, 600, 800, and 1000 mg/L). The median lethal concentration (LC50) was determined at 10 and 15 min of exposure. Results showed that ABZ was 100% effective in killing P. cochlearii, achieving complete mortality at 15 min with a concentration of 600 mg/L, and at 30 min with 200 mg/L. The LC50 value decreased over time, with 618.91 mg/L at 10 min and 260.32 mg/L at 15 min, indicating a cumulative effect of ABZ on metacestode tissues. In conclusion, ABZ is an effective treatment against cestode infestations, and further evaluation under experimental and commercial scales is recommended to establish control protocols in aquaculture systems.

Aeromonas hydrophila-induced bacterial sepsis is a major threat to aquaculture, characterised by excessive inflammation, ferroptosis (an iron-dependent lipid peroxidation-driven cell death) and oxidative damage, which collectively lead to high mortality. Taurine (TAU) and glutathione (GSH) have been demonstrated to have potential therapeutic efficacy against ferroptosis-associated pathologies through redox modulation. However, their combined effects and underlying mechanisms in alleviating A. hydrophila infection remain unclear. In this study, we investigated the protective roles of TAU, GSH and their combination in vitro using yellow catfish (Pelteobagrus fulvidraco) macrophages and grass carp (Ctenopharyngodon idella) kidney (CIK) cells and in vivo using yellow catfish challenged with A. hydrophila. The results showed that TAU and GSH, either alone or in combination, alleviated oxidative stress by significantly reducing reactive oxygen species (ROS) accumulation and inhibited nuclear factor-κB (NF-κB) pathway activation. This led to downregulated expression of pro-inflammatory cytokines (IL-1β and TNF-α) and upregulated anti-inflammatory cytokines (IL-10 and TGF-β), accompanied by alleviated ferroptosis. In vivo, dietary supplementation with TAU (10 g/kg) or GSH (350 mg/kg) alone improved survival rates (51.7% and 38.3%, respectively), reduced tissue bacterial loads and protected intestinal and hepatic tissues by preserving mucosal barrier function. However, the TAU + GSH combination unexpectedly decreased survival (28.3%) due to excessive immunosuppression (overproduction of IL-10 and TGF-β) and impaired mucosal barrier, which exacerbated pathogen colonisation. Together, our findings demonstrate that TAU and GSH alleviate A. hydrophila-induced oxidative stress by reducing mitochondrial ROS overproduction and disrupting the ROS/NF-κB signalling pathway, thereby attenuating inflammatory cytokine storms and ferroptosis. These results provide novel insights into the pathological mechanisms of bacterial sepsis in fish and develop sustainable strategies to improve disease resistance in aquaculture.

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.