Journal of fish diseases最新文献

{"title":"Temperature, Disinfectant Concentration and Bacterial Innate Properties Influence the Disinfection of Bacterial Pathogens Relevant to Catfish Aquaculture","authors":"Aloysius Chimezie Adibe,&nbsp;Margaret Crumlish","doi":"10.1111/jfd.70216","DOIUrl":"10.1111/jfd.70216","url":null,"abstract":"<p>Aquaculture systems suffer a wide range of losses, mostly due to bacterial disease outbreaks, and the use of disinfectants is a routine practice for controlling the spread of pathogenic organisms globally. Including <i>Aeromonas hydrophila</i>, <i>Streptococcus agalactiae</i> and <i>Edwardsiella tarda</i>, implicated for natural disease outbreaks and economic losses in catfish culture systems. Unfortunately, suboptimal disinfection practices are widespread within catfish aquaculture systems, and information on the factors influencing disinfection efficacy is limited. In this study, the efficacy of Virkon aquatic disinfectant against pathogenic strains of <i>A. hydrophila</i>, <i>S. agalactiae</i> and <i>E. tarda</i> was investigated by measuring changes in absorbance and viable colony counts at 22°C, 28°C and 34°C. The in vitro assays were conducted via broth microdilution suspension and carrier test methods to investigate the influence of disinfectant concentration, strain variation and temperature fluctuations on disinfection efficacy within catfish aquaculture systems. The results revealed that 0.125% was the MIC and MBC for the <i>S. agalactiae</i> strains under all the experimental conditions in both tests. However, at 28°C and 34°C, the MIC and MBC were 0.25% for <i>A. hydrophila</i> strains in the suspension test and 0.5% for the carrier test. Among all the strains, <i>E. tarda</i> presented the highest level of resistance to the disinfectant, with 1% MBC in the carrier test at 22°C and 28°C. In addition, the MIC value for strains of <i>A. hydrophila</i> and <i>E. tarda</i> was 0.25% at 28°C and 34°C in the suspension test, and both species had the same MBCs of 0.25% at 28°C in the suspension test and 0.5% at 34°C in the carrier test. Overall, changes in temperature, disinfectant concentration and intrinsic bacterial factors were identified as the principal factors that influenced the disinfection efficacy of Virkon aquatic disinfectant. Our findings identified suboptimal sanitation practices as high aquaculture biosecurity risk and emphasized that the carrier test is an ideal method for evaluating the efficacy of chemical disinfectants applied in the context of aquaculture.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":"49 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jfd.70216","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148101404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Francisella orientalis in Aquacultured Tilapia (Oreochromis spp.): A Case Work-Up of Diagnostics and Pathologic Findings in the North Central Region (USA).","authors":"S E Edmonds, N O Hickey, C Q Reis, I Kamonchai, M J Kebus, A P Pessier, T B Waltzek, K R Snekvik","doi":"10.1111/jfd.70297","DOIUrl":"https://doi.org/10.1111/jfd.70297","url":null,"abstract":"<p><p>Tilapia (Oreochromis spp.) is an increasingly popular aquacultured fish worldwide. While tilapia enjoy a 'hardy-fish' reputation among fish farmers, they are susceptible to a variety of infectious diseases that can be difficult to recognize pondside and have similarities in their gross presentations. This report describes gross and microscopic dermal, renal, and splenic granulomas; isolation and identification of Francisella orientalis; intervention; and resolution of a F. orientalis outbreak in an aquaculture farm in the North Central United States where F. orientalis has not been reported previously. The outbreak resulted in peak daily mortality rates of approximately 2.7%. This case report highlights the current benefits of aquatic species-focused diagnostic testing for fish farmers at veterinary diagnostic labs and provides an anecdotal clinical example of a resolved francisellosis outbreak potentially influenced by increasing the water temperature.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70297"},"PeriodicalIF":2.3,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149074859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phylogenomic Diversity, Serotype Heterogeneity and In Vivo Virulence of Flavobacterium psychrophilum Isolates From Rainbow Trout Farms in Türkiye.","authors":"Soner Altun, Gorkem Tasci, V Can Bozaba, Nihed Ajmi, Muhammed Duman, Cuneyt Ozakin, Nazmiye Ulku Tuzemen, Sebahattin Ergün, Sevdan Yılmaz, Izzet Burcin Saticioglu","doi":"10.1111/jfd.70295","DOIUrl":"https://doi.org/10.1111/jfd.70295","url":null,"abstract":"<p><p>Flavobacterium psychrophilum, the causative agent of bacterial cold-water disease (BCWD) and rainbow trout fry syndrome (RTFS), remains one of the most important bacterial pathogens affecting salmonid aquaculture. In this study, 24 F. psychrophilum isolates recovered during a 12-month surveillance programme from two rainbow trout farms in Türkiye were characterized using phenotypic, serological, antigenic, phylogenomic and experimental infection approaches. Phylogenomic analyses showed that most isolates belonged to CC-ST10, whereas four isolates were assigned to the CC-ST90/ST108 lineage, representing the first report of this lineage in Türkiye. Comparative genomic analysis revealed extensive conservation of virulence-associated loci, with only FP0006 and FP0506 showing variable distribution among isolates. Notably, FP0506 was absent exclusively from ST108/CC-ST90 isolates. Experimental immersion challenge assays demonstrated that all selected isolates were able to induce mortality in rainbow trout under the conditions tested. However, isolate-dependent differences in survival were not statistically significant in the standard immersion model and became more evident following H₂O₂ pre-treatment, with the FP1 group showing the lowest survival. These findings suggest that in vivo pathogenicity may be influenced by host barrier status and cannot be fully predicted by phylogenomic lineage, serotype or in vitro virulence-associated phenotypes alone. Phenotypic serotyping identified Th as the predominant serotype, although discrepancies were observed between phenotypic and genome-based serotype classifications. Whole-cell protein profiling and Western blot analyses revealed both antigenic heterogeneity and conserved immunoreactive structures across phylogenetically distinct isolates. Antimicrobial susceptibility testing showed a high proportion of non-wild-type phenotypes for oxytetracycline, florfenicol and enrofloxacin; however, no acquired antimicrobial resistance genes were detected by genome-based screening. Collectively, these findings demonstrate that Turkish F. psychrophilum populations are phylogenomically diverse but retain largely conserved virulence-associated loci and immunoreactive antigenic structures. This study provides the first evidence of the CC-ST90/ST108 lineage in Türkiye and highlights the value of integrating genomic, serological, phenotypic, antigenic and experimental infection data for understanding the population structure, serotype heterogeneity and pathogenic potential of F. psychrophilum in rainbow trout aquaculture.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70295"},"PeriodicalIF":2.3,"publicationDate":"2026-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149038237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Establishment of a Novel Primary Cell Culture Model for the Continuous Propagation of Carp Edema Virus In Vitro.","authors":"Yue Liu, Zuwei Zhang, Sixuan Peng, Kim Jong Su, Xuanyu Ren, Xiaonan Lv, Jinshan Huang, Xu Lin, Wen Shi, Min Liu","doi":"10.1111/jfd.70296","DOIUrl":"https://doi.org/10.1111/jfd.70296","url":null,"abstract":"<p><p>Koi sleepy disease (KSD), also called carp edema virus disease (CEVD), is a widespread viral infection affecting common carp (Cyprinus carpio) and its ornamental varieties, leading to substantial economic losses in global aquaculture. The development of effective prophylactic and therapeutic measures against CEVD has been hampered by the lack of a robust system for in vitro propagation of its causative agent, carp edema virus (CEV). To address this constraint, a method was established for the isolation and continuous culture of CEV using primary head kidney cells derived from Songpu mirror carp. A highly pathogenic CEV strain, L-3, isolated from an outbreak in Liaoning, China, was successfully propagated in vitro through progressive adaptation during serial passage. Pronounced cytopathic effects (CPE) were observed over 17 consecutive passages, with CEV presence confirmed in each passage by nested PCR. Viral replication dynamics, assessed across 20 successive passages, demonstrated a progressive increase in viral copy numbers from very low levels at initial passage to peak at passage 18, confirming successful adaptation to primary head kidney cells. Challenge trials with the 20th-passage virus induced clinical signs characteristic of KSD in carp. Moreover, examination of gill tissues from infected fish by transmission electron microscopy revealed viral particles with morphology typical of CEV. The present work reveals a novel approach for the propagation of CEV in vitro. These findings are expected to provide a critical tool for advancing fundamental research on viral pathogenesis and supporting the systematic development and evaluation of vaccines against CEVD.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70296"},"PeriodicalIF":2.3,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149030780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variable Infection Outcomes in Repeated Experimental Challenges of Atlantic Salmon (Salmo salar) With an Infectious Salmon Anaemia Virus Isolate.","authors":"Lars Ole Sti Dahl, Stine Braaen, Øystein Wessel, Johanna Hol Fosse, Espen Rimstad","doi":"10.1111/jfd.70291","DOIUrl":"https://doi.org/10.1111/jfd.70291","url":null,"abstract":"<p><p>Infectious salmon anaemia (ISA) affects Atlantic salmon (Salmo salar) and is caused by the ISA virus (ISAV). The disease is associated with ISAV strains with deletions in the hemagglutinin-esterase protein, named HPRΔ variants. The present study was initially designed as a vaccine efficacy study against ISA. Considerable variability in mortality in virus-injected fish was observed in repeated experimental challenges using the NO/Finnmark/NVI-70-72/2020 isolate. Four independent experimental challenge trials were conducted. In two experiments, high cumulative mortality was seen in intraperitoneally (i.p.) injected fish. In contrast, considerably lower cumulative mortality was observed in i.p. injected fish in two other experiments. Mortality among cohabitant fish was moderate in one experiment and low or absent in two others. The observed inconsistency precluded reliable assessment of vaccine efficacy and implied investigation into factors underlying the outcome reproducibility between the experimental challenges. To investigate the observed variation in outcomes, fish, virus, and physical conditions were compared in detail. One notable difference among the challenge experiments was tank volume. Mortality was higher among fish injected with virus in smaller tanks than in larger ones. Further examination of the physical and biological variables failed to identify any other definitive determining factors. In addition, to investigate whether the comparatively delayed mortality induced by the injected NO/Finnmark/NVI-70-72/2020 isolate was associated with early virus-host interactions, a time-course study was conducted to quantify relative viral RNA levels and innate immune responses in ASK-II cells. A highly virulent isolate induced greater expression of innate immune response genes, which may be attributable to the higher amount of viral RNA present in the inoculum despite comparable levels of infectious virus. Collectively, these findings suggest that subtle differences in experimental conditions may contribute to variation in disease outcome and indicate that further research is required to improve understanding of fundamental ISAV biological characteristics.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70291"},"PeriodicalIF":2.3,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149017086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Species Diversity, Antimicrobial Susceptibility, and Provisional Epidemiological Cut-Off Values of Vibrio spp. Isolated From Pacific White Shrimp (Litopenaeus vannamei) Farms in Southern Thailand.","authors":"Tirawat Rairat, Arunothai Keetanon, Lalitphan Kitsanayanyong, Anurak Uchuwittayakul, Natnicha Chongprachavat, Thanakrit Ratanaprapaporn, Parattagorn Wimanhaemin, Papatchaya Vatayanont, Chittakorn Yutthawichai, Niti Chuchird","doi":"10.1111/jfd.70292","DOIUrl":"https://doi.org/10.1111/jfd.70292","url":null,"abstract":"<p><p>Vibrio spp. are the most common opportunistic pathogens in shrimp farms, and drug-resistant Vibrio spp. pose a major threat to both shrimp and human health. The current study investigated species diversity and antimicrobial susceptibility of Vibrio spp. from Pacific white shrimp (Litopenaeus vannamei) in Southern Thailand. Shrimp were collected from ten intensive farms with a history of disease outbreaks. Vibrio spp. were isolated from the hepatopancreas, identified to species level via 16S rRNA sequencing, and tested for minimum inhibitory concentrations (MICs) against eight antibiotics. A total of 27 Vibrio species were recovered. V. parahaemolyticus was the most frequently recovered species among the selected isolates, followed by V. alginolyticus and V. harveyi. Overall, the isolates were susceptible to oxytetracycline, doxycycline, ciprofloxacin, enrofloxacin, and florfenicol, with MIC₅₀ ranging from ≤ 0.25 to 2 μg/mL. Conversely, most Vibrio spp. were resistant to amoxicillin, ceftriaxone, and sulfadimethoxine, with MIC₅₀ values of at least 128 μg/mL. To our knowledge, this study provides the first evidence of high-level ceftriaxone resistance in Vibrio spp. from farmed shrimp. To distinguish fully susceptible bacteria (wild type) from those that develop acquired resistance, epidemiological cut-off (CO_WT) was determined. The CO_WT for florfenicol was calculated as ≤ 4 μg/mL; when this threshold was applied to the Vibrio spp. isolates, 83.10% were classified as wild type. Our findings highlight the need for strict regulation of antibiotic use in shrimp aquaculture to minimize the emergence and spread of antibiotic-resistant bacteria.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70292"},"PeriodicalIF":2.3,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149012599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of a Multiplex Quantitative PCR Assay for Simultaneous Detection of Multiple Vibrio Species in Aquaculture Samples.","authors":"İnci Başak Müştak, Hamit Kaan Müştak, Seyyide Sarıçam İnce, Doğukan Uğun, Görkem Cengiz, Gültekin Ünal, Ebru Torun, Muammer Göncüoğlu","doi":"10.1111/jfd.70289","DOIUrl":"https://doi.org/10.1111/jfd.70289","url":null,"abstract":"<p><p>Aquaculture associated Vibrio species are important bacterial pathogens causing significant economic losses in aquaculture and zoonotic infections in humans. Rapid and accurate detection of Vibrio species is therefore essential for diagnosis, surveillance and control. In this study, a multiplex quantitative PCR (qPCR) assay was developed for the simultaneous detection of Vibrio spp. together with V. alginolyticus, V. anguillarum, V. harveyi, V. ordalii, V. parahaemolyticus, V. vulnificus and V. cholerae. Species-specific primers and probes targeting ompA, glutamate synthase, mreB, vohB, dnaJ, gyrB and lolB genes were designed, while the rpoA gene was selected for genus level Vibrio detection. The assay demonstrated 100% inclusivity for all target strains without cross reactivity against non-target bacterial species. PCR efficiency/inhibition analyses showed stable amplification dynamics across serial dilutions, with R² values above 0.99, amplification efficiencies between 96.8% and 98.2%, and ΔCq values ≤ 0.13 for all targets. Limit of detection (LOD) studies performed using artificially contaminated matrices demonstrated a detection limit of 10¹-10⁰ CFU/mL for all targets, with detection performance comparable to the culture-based recovery method. Overall, the developed multiplex qPCR assay provides a rapid, sensitive and analytically reliable approach for simultaneous detection of multiple Vibrio species associated with aquaculture and zoonotic infections.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70289"},"PeriodicalIF":2.3,"publicationDate":"2026-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149012564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Divergent Healing Trajectories Among Common Mechanical Skin Wound Types in Post-Smolt Atlantic Salmon (Salmo salar Linnaeus, 1758).","authors":"Kasidis Chaiyasut, Rose Ruiz Daniels, Christian Karlsen, Barry Bradford, Gunhild Seljehaug Johansson, Miroslava Hansen, Marta Bou, Marianne Vaadal, Lene Rydal Sveen","doi":"10.1111/jfd.70290","DOIUrl":"https://doi.org/10.1111/jfd.70290","url":null,"abstract":"<p><p>Mechanical wounds are a common form of skin damage in Atlantic salmon (Salmo salar Linnaeus, 1758) aquaculture and can predispose fish to secondary infections. Such wounds often arise from routine farming practices, including delousing operations. Although visually similar, different types of mechanical injury may trigger distinct healing processes, which remain poorly understood. To investigate this, post-smolt Atlantic salmon were subjected to three wound models: scale loss, superficial wounds involving the epidermis and dermis, and deep wounds extending through all skin layers. Responses were assessed at 2 days and 5 weeks post-wounding to capture different phases of skin wound healing. The injuries were characterised using serum parameters, stereomicroscopy, histology, immunohistochemistry for cell proliferation, quantitative polymerase chain reaction (qPCR), and RNAscope analysis of T cell markers. Despite their initially similar appearance, scale loss and superficial lesions followed markedly different healing trajectories. Fish with scale removal mostly recovered to the pre-damage state within 5 weeks, whereas superficial damage elicited a delayed healing response similar to that of deep wounds. Each wound type exhibited distinct epidermal and hypodermal alterations, highlighting differences among wound types that should be considered by fish health personnel and farmers.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70290"},"PeriodicalIF":2.3,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148977138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First Report of Halomonhystera sp. cf. disjuncta Associated With Branchial and Cutaneous Lesions During a Mortality Event in Laboratory-Acclimated Olive Flounder (Paralichthys olivaceus).","authors":"Hyo-Young Kang, Ju-Yeop Lee, Young-Ung Heo, Cho-Yoon Shin, Thanh Luan Nguyen, Do-Hyung Kim","doi":"10.1111/jfd.70287","DOIUrl":"https://doi.org/10.1111/jfd.70287","url":null,"abstract":"<p><p>This clinical report describes a mortality event associated with a free-living marine nematode provisionally assigned to the Halomonhystera disjuncta species complex (Halomonhystera sp. cf. disjuncta) in laboratory-acclimated olive flounder (Paralichthys olivaceus). Fish were acclimated at 13°C in filtered seawater with 50% daily water exchange. Affected fish developed caudal fin erosion, gill pallor, excessive branchial mucus, abnormal posture and, in larger fish, cutaneous ulcers. Cumulative losses within 1 month reached approximately 50% in the 10 g groups and 30% in the 100 g group. Microscopy revealed numerous nematodes in branchial mucus, adjacent to gill lamellae and in fin erosions and skin ulcers. Morphologically similar nematodes were recovered from the seawater filtration line but were not molecularly confirmed. VHSV was not detected by RT-qPCR at stocking or during the mortality event, and outbreak-associated PCR assays yielded no target-specific amplification for Tenacibaculum maritimum, Cryptocaryon irritans, or Ichthyobodo spp. Partial 18S rRNA and ITS sequences showed 100% identity to GenBank sequences assigned to H. disjuncta. Because this complex contains cryptic lineages, the nematode was conservatively designated Halomonhystera sp. cf. disjuncta. Although causality was not established, the findings support a clinicopathological association with branchial and cutaneous lesions.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70287"},"PeriodicalIF":2.3,"publicationDate":"2026-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148963107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isolation and Characterisation of Aeromonas hydrophila, Aeromonas veronii and Vibrio cholerae O139 From Diseased Bester Sturgeon (Huso huso × Acipenser ruthenus): A Case Report.","authors":"Petya Stefanova Orozova, Dimitar Petrov Ivanov, Deyan Stratev Stratev, Radostin Stefanov Simeonov, Ivelina Hubenova Grozeva, Pavel Istiliyanov Rashev","doi":"10.1111/jfd.70280","DOIUrl":"https://doi.org/10.1111/jfd.70280","url":null,"abstract":"<p><p>This study investigated bacterial pathogens associated with disease and mortality in farmed bester sturgeon (Huso huso × Acipenser ruthenus) reared in freshwater cages in the Vacha Reservoir, Bulgaria. Affected fish exhibited lethargy, anorexia, haemorrhagic skin lesions and multifocal internal pathology. Histological examination revealed hepatic degeneration and vacuolar change, consistent with systemic bacterial infection. Bacterial isolates recovered from blood and internal organs were identified as Aeromonas hydrophila, A. veronii and Vibrio cholerae O139 using culture-based methods, MALDI-TOF MS, species-specific PCR and 16S rRNA gene sequencing. Virulence profiling showed that A. hydrophila carried multiple virulence-associated and enterotoxin genes, whereas A. veronii possessed only aerA. The V. cholerae O139 isolate lacked ctxA and rfbO1, confirming a non-toxigenic profile. In vivo infection trials with clinical sturgeon isolates A. hydrophila HGM24 and V. cholerae O139 GM24 produced dose-dependent mortality, demonstrating the pathogenic potential of both isolates. This case represents the first concurrent detection and characterisation of A. hydrophila, A. veronii and V. cholerae O139 in bester sturgeon in Bulgaria. It underscores the importance of integrated diagnostic approaches combining pathogen identification, virulence assessment, histopathology and experimental infection in freshwater aquaculture disease investigations.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70280"},"PeriodicalIF":2.3,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148956021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}