Journal of fish diseases最新文献

{"title":"Impact of Surveillance and Depopulation Strategies on Fish Disease Transmission Among Net-Cage Farms Near the Tongyeong Coast Based on a Spatiotemporal Hybrid Approach.","authors":"Gyoungsik Kang, Ju-Sung Kim, Kyung-Ho Kim, HyeongJin Roh","doi":"10.1111/jfd.70272","DOIUrl":"https://doi.org/10.1111/jfd.70272","url":null,"abstract":"<p><p>Infectious diseases among fish farms present significant challenges to fish health and production. Horizontal transmission serves as one of the main mechanisms driving outbreaks in these settings. The dynamics of horizontal transmission are influenced by pathogen properties, host characteristics and environmental factors. Additionally, the implementation of epidemiological interventions can further shape the patterns and consequences of infectious disease spread. However, there is a paucity of studies assessing how specific epidemiological measures, such as timely disease surveillance and strategic depopulation, influence transmission and outbreak outcomes. This study utilized a spatiotemporal hybrid model to assess pathogen dissemination following an infectious disease event in Tongyeong, a prominent area for floating net cage aquaculture in Korea. We investigated how variations in sampling intensity affected the timing of disease detection and analysed the impact of two control strategies (immediate culling upon detection versus no culling) on the progression of disease and fish mortality. Findings revealed significant differences in disease detection timing and probability based on the surveillance sampling size. Early detection of disease was achieved when 100 fish were sampled, as opposed to a delayed response when only 5 fish were tested. Furthermore, the conditions under which surveillance occurred had a notable impact on both the spatial spread and the success of depopulation measures. Generally, prompt detection followed by immediate depopulation led to a decrease in disease-related mortality over a wider area. However, this method also necessitated culling a substantially greater number of fish. Although the impact of these interventions may be influenced by geographical and environmental variables, our results suggest that the utility of depopulation strategies is closely linked to the efficacy of surveillance efforts and the epidemiological profile of the infection, such as its associated mortality rate and transmissibility.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70272"},"PeriodicalIF":2.3,"publicationDate":"2026-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148764805","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":"Targeting Peroxiredoxin 6: Tannic Acid Inhibits Singapore Grouper Iridovirus Infection via PRDX6-Dependent Pathway and Antioxidant Response.","authors":"Xiangmou Qin, Chen-Ao Li, Lin Huang, Qing Yu, Mingming Zhao, Yanxia Gao, Jiaxi Li, Jia Cai, Huapu Chen, Fei Ling, Junxiang Lai, Ermeng Yu, Mingzhu Liu, Pengfei Li","doi":"10.1111/jfd.70273","DOIUrl":"10.1111/jfd.70273","url":null,"abstract":"<p><p>Singapore grouper iridovirus (SGIV) is a major viral pathogen threatening grouper aquaculture. The lack of specific antiviral drugs underscores the urgent need to develop safe and effective control strategies. This study demonstrates that tannic acid (TA) exhibits significant anti-SGIV activity in vitro. In grouper spleen (GS) cells, TA inhibited SGIV replication in a concentration-dependent manner. Time-of-addition assays confirmed its antiviral efficacy when applied either before or after SGIV infection. Mechanistically, TA directly interfered with SGIV particle infectivity, viral adsorption, entry and intracellular replication. Network pharmacology analysis suggested TA's targets are associated with host cellular antioxidant pathways, among which Peroxiredoxin 6 (PRDX6) was identified as a potential target of TA. Further experiments confirmed that TA upregulated the Nrf2 antioxidant pathway and suppressed the expression of pro-inflammatory cytokines (IL-1β, IL-8). Notably, TA enhanced the expression of PRDX6, and overexpression of PRDX6 significantly inhibited SGIV replication, indicating that PRDX6 contributes to the antiviral effect of TA. In vivo, TA treatment not only restored PRDX6 expression in infected groupers but also significantly reduced viral load in liver and spleen following SGIV infection. These findings demonstrate that TA inhibits SGIV through direct viral interference and PRDX6-mediated antioxidant modulation, highlighting its potential as a natural therapeutic agent against SGIV.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70273"},"PeriodicalIF":2.3,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148725039","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":"Ontogenetic Development of Hyperostosis in the Crevalle Jack Caranx hippos (Linnaeus, 1766) and New Records of Affected Bone Regions.","authors":"Camila Vitória Gonçalves Ferreira, Davi Lettieri Santos Dos Abrahão, Alice Miranda Cardoso de-Sá, Alice Barbosa Henriques, Ana Julia Araujo Rosa D' Almeida Lima, Maykon Victor Rezende de Oliveira, Márcia Carolina Salomão, Helena Passeri Lavrado, Fernando Augusto Pereira Tuna","doi":"10.1111/jfd.70270","DOIUrl":"https://doi.org/10.1111/jfd.70270","url":null,"abstract":"<p><p>Hyperostosis is a non-pathological condition widely reported in marine teleosts, yet its developmental dynamics and underlying drivers remain poorly understood. This study investigates the ontogenetic progression and anatomical distribution of hyperostosis in Caranx hippos based on a growth series of 39 specimens collected along the Brazilian coast. Individuals were categorised into two size classes (class 1 < 400 mm and class 2 ≥ 400 mm), and skeletal alterations were assessed through radiographic imaging, morphometric analyses and histology. Hyperostosis was detected in 87.2% of specimens and affected nine skeletal regions, including dorsal and anal pterygiophores, cleithrum, ribs, pelvic bones, neural and hemal spines and for the first dorsal fin pterygiophore, preopercle and opercle. The dorsal pterygiophores were the earliest and most consistently affected elements, with detectable changes in individuals as small as 184 mm TL, suggesting an early onset of the condition. Other regions exhibited a size-dependent pattern, with hyperostosis appearing sequentially and increasing in frequency and extent with growth. Morphological variation among skeletal elements indicates region-specific expression, with pronounced differences in thickness, width and mass between hyperostotic and non-hyperostotic bones. Comparisons with previous studies confirm a species-specific pattern of hyperostotic distribution in C. hippos, with minor variation in the onset and extent of affected regions. The observed ontogenetic progression supports the hypothesis that hyperostosis develops sequentially across skeletal elements rather than simultaneously. These findings, combined with ecological and biomechanical considerations, suggest that hyperostosis results from multiple interacting factors, including growth-related mechanical loading and environmental variability. Overall, this study provides a comprehensive characterisation of hyperostotic development in C. hippos, highlighting the importance of ontogenetic approaches for understanding the biological and functional significance of this condition in marine fishes.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70270"},"PeriodicalIF":2.3,"publicationDate":"2026-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148701475","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":"Immunogenicity and Protective Efficacy of the First Autogenous Aeromonas hydrophila Vaccine for Piaractus brachypomus.","authors":"Layana Aparecida Batista Pereira, Juliana do Nascimento Ferreira, Laine Patricia Costa Dos Santos, Larissa Andréia Ferreira Sampaio, Igor Bartolomeu Alves de Barros, Elizabeth Gusmão Affonso, Jefferson Yunis-Aguinaga, Gustavo da Silva Claudiano","doi":"10.1111/jfd.70271","DOIUrl":"https://doi.org/10.1111/jfd.70271","url":null,"abstract":"<p><p>Aeromonas hydrophila is a major zoonotic bacterial pathogen responsible for haemorrhagic septicemia, substantial economic losses in aquaculture and increasing antimicrobial resistance among field isolates. It is also one of the main bacterial species associated with mortality outbreaks in pirapitinga, Piaractus brachypomus, culture in the Amazon region of Latin America. Therefore, this study evaluated the immunogenicity and protective efficacy of the first autogenous vaccine against A. hydrophila developed for P. brachypomus, formulated with or without a Montanide adjuvant. A total of 150 fish were vaccinated by intraperitoneal injection with a formalin-inactivated homologous bacterin and, at 35 days post-vaccination, challenged with a homologous strain of A. hydrophila at the median lethal dose (LD₅₀). Following bacterial challenge, biological samples were collected at 24 h post-challenge, and survival was monitored for 15 days (50-day trial period). The vaccinated groups showed enhanced immune responses, characterized by increased ROS levels, lysozyme activity, agglutinating antibody titers and IgM levels, particularly in the fish vaccinated with the adjuvant. Haematological evaluation revealed lymphocytosis and, morphologically, lower lesion severity and preservation of renal architecture in vaccinated groups. In contrast, infected non-vaccinated fish exhibited leukopenia, tubular disorganization, intense mononuclear inflammatory infiltrates, glomerular alterations and lesions suggestive of tissue necrosis. These findings were reflected in enhanced protection following the bacterial challenge, with relative percent survival (RPS) values of 76.19% for fish vaccinated without the adjuvant and 85.71% for those vaccinated with the adjuvant. Overall, the autogenous vaccine was safe, immunogenic and provided effective protection against Aeromonas hydrophila infection in Piaractus brachypomus.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70271"},"PeriodicalIF":2.3,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148689202","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":"Field-Deployable RPA-CRISPR/Cas12a Detection of Decapod Iridescent Virus 1 in Shrimp.","authors":"Rui Wang, Yanfeng Wang, Lihan Wang, Yishuai Du, Huiqin Tian, Tianlong Qiu, Liang Chi","doi":"10.1111/jfd.70269","DOIUrl":"https://doi.org/10.1111/jfd.70269","url":null,"abstract":"<p><p>Decapod iridovirus 1 (DIV1) is a highly lethal pathogen that infects decapod crustaceans including Litopenaeus vannamei, causing mass mortality in cultured shrimp and severe economic losses worldwide. The ATPase gene is a highly conserved region within the DIV1 genome, plays a critical role in viral replication and represents an ideal target for molecular diagnostic development. In this study, we established a rapid, sensitive and field-adaptable detection platform for DIV1 by integrating recombinase polymerase amplification (RPA) with the CRISPR/Cas12a system. RPA enables efficient isothermal amplification of target nucleic acids, achieving exponential enrichment of the target nucleic acids and exerting the function of signal amplification. While the CRISPR/Cas12a system upon crRNA-guided specific recognition of the amplicon, triggers robust trans-cleavage activity against reporter probes for signal generation and readout. After systematic optimization, the RPA reaction was performed at 38°C for 10 min and the CRISPR-Cas12a reaction was conducted at 37°C for 20 min. The integrated two-step workflow completed detection within 40 min, with a limit of detection of 2.3 × 10¹ copies/μL. Specificity evaluation confirmed that the RPA-CRISPR/Cas12a assay exclusively recognised DIV1 without cross-reaction with other major shrimp pathogens. Further validation using clinical shrimp samples demonstrated stable and reliable performance, supporting its practical utility in aquaculture settings. In conclusion, the established CRISPR/Cas12a-based detection platform provides a robust technical tool for early warning and on-site rapid screening of DIV1, facilitating timely disease control and risk management in shrimp farming.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70269"},"PeriodicalIF":2.3,"publicationDate":"2026-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148678972","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":"Discovery of a Novel Alloherpesvirus in Diseased Turbot in China.","authors":"Wenli Liu, Qihang Tu, Yueqi Wu, Jing Li, Wei Lin, Fengjuan Tian, Wenguang Xu, Shan Xu, Yigang Tong","doi":"10.1111/jfd.70239","DOIUrl":"https://doi.org/10.1111/jfd.70239","url":null,"abstract":"","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70239"},"PeriodicalIF":2.3,"publicationDate":"2026-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148673724","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":"Melanized Focal Changes in the Fillets of Farmed Atlantic Salmon: A Clinical Report From a Deep-Sea Production Site","authors":"Håvard Bjørgen,&nbsp;Marit Svendby,&nbsp;Alexander Figenschou,&nbsp;David Persson,&nbsp;Daniel Lauritzen,&nbsp;Marit Stormoen,&nbsp;Erling Olaf Koppang","doi":"10.1111/jfd.70180","DOIUrl":"10.1111/jfd.70180","url":null,"abstract":"<div>\u0000 \u0000 <p>Melanized focal changes (MFCs) are a persistent challenge in Atlantic salmon (<i>Salmo salar</i>) aquaculture, affecting product quality and fish welfare. These lesions are generally considered to arise from red focal changes (RFCs), which are often attributed to handling-related trauma, but underlying mechanisms remain poorly understood. In this case report, we investigated the occurrence and histopathological features of RFCs and MFCs in farmed Atlantic salmon reared in a submerged deep-sea system, where handling disturbances were minimized. Environmental conditions, including dissolved oxygen levels, were monitored throughout production. Macroscopic lesions exhibiting red, black or mixed discoloration were sampled from the ventral fillet at slaughter (average weight 3.3 kg) and examined histologically. RFCs showed haemorrhage, adipocyte necrosis, extracellular lipid release and early pseudocyst formation within adipose tissue. MFCs displayed diffuse granulomatous inflammation dominated by foamy and pigmented macrophages, with lipid-filled pseudocystic structures and persistent adipose involvement. Lesions exhibited a polyphasic pattern consistent with fat necrosis–associated inflammation. The presence and progression of RFCs into MFCs under submerged, minimally handled conditions demonstrate that handling-related trauma is not necessary for lesion initiation. The strong association with adipose tissue suggests endogenous processes—related to lipid metabolism, tissue vascularization, local hypoxia or nutrition—play a central role. Declining environmental oxygen preceding slaughter may exacerbate hypoxia within affected tissues, although its precise influence remains unclear. These findings refine current concepts of MFC pathogenesis and emphasize intrinsic biological drivers over mechanical injury in the development of these lesions in Atlantic salmon.</p>\u0000 </div>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":"49 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147618898","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":"Sea Lice (Lepeophtheirus salmonis) Harbour Putative Fish Pathogens: Insights From Illumina and Nanopore Sequencing","authors":"B. Klimesova,&nbsp;N. M. Ruane,&nbsp;R. Domingo-Bretón,&nbsp;F. Moroni,&nbsp;F. Naya-Català,&nbsp;J. Pérez-Sánchez,&nbsp;K. O'Dwyer,&nbsp;O. Lyashevska,&nbsp;H. Rodger,&nbsp;A. Talbot","doi":"10.1111/jfd.70182","DOIUrl":"10.1111/jfd.70182","url":null,"abstract":"<p>Ectoparasites that penetrate host skin can act as biological or mechanical vectors for pathogens and, in some cases, serve as reservoirs. Crustacean ectoparasites of fish are potential vectors of pathogens, which is especially relevant for obligate pathogens (e.g., <i>Aeromonas salmonicida</i>) with limited seawater survival. Sea lice (<i>Lepeophtheirus salmonis</i>), affecting Atlantic salmon, cause dermal damage and can facilitate secondary infections, resulting in economic losses. While the physical impact of sea lice is well known, their role in pathogen transmission is less clear. The gut bacterial microbiome of lice collected over four months from a salmon farm in Ireland was analysed using Illumina MiSeq and Oxford Nanopore Technologies (ONT) PromethION sequencing for comparison. Illumina and Nanopore sequencing identified 15 and 24 genera of known fish pathogens, respectively. Moreover, Nanopore data revealed up to 15 putative pathogenic species, including <i>Tenacibaculum maritimum, T. dicentrarchi</i> and <i>Vibrio anguillarum</i>, causative agents of tenacibaculosis and vibriosis. The results of this study provide a gut bacterial microbiome characterisation of <i>L. salmonis</i> in a commercial aquaculture setting and demonstrate the potential of sea lice to act as pathogen vectors or reservoirs. These findings have important implications for pathogen surveillance, management, and prevention strategies in salmon aquaculture.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":"49 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jfd.70182","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147638523","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":"Nodular Lesions in the Pyloric Caeca of Sardinella aurita (Teleostei) Associated With the Cestode Anthobothrium sp. 1 Larvae (Platyhelminthes: Eucestoda) Off Tunisia, Mediterranean Sea.","authors":"Chiraz Ben Saad, Jean-Lou Justine, Jihene Jouini, Delphine Gey, Stefan Theisen, Harry W Palm, Lamia Gargouri","doi":"10.1111/jfd.70267","DOIUrl":"10.1111/jfd.70267","url":null,"abstract":"<p><p>Examination of round sardinella Sardinella aurita Valenciennes, 1847 (Clupeidae) from the Gulf of Tunis (Tunisia) revealed the first local and Mediterranean record of Anthobothrium sp. 1 sensu Jensen & Bullard, 2010 (Tetraphyllidea incertae sedis, Anthobothrium). Nodular lesions containing multiple larvae were detected at the proximal end of the pyloric caeca, and free plerocercoids were observed in the intestinal lumen and stomach. The newly generated LSU rDNA sequences shared 100% nucleotide identity with adult Anthobothrium sp. 1B from the blacktip shark Carcharhinus limbatus Valenciennes, 1839 and larvae from the largehead hairtail Trichiurus lepturus L., both collected from the Gulf of Mexico (Florida and Mississippi, USA). Furthermore, they exhibited a minor 2.1% sequence divergence from related lineages within the same complex found in the Atlantic sharpnose shark Rhizoprionodon terranovae Richardson, 1836 and the hardhead sea catfish Ariopsis felis (Linnaeus, 1766) from the same Gulf of Mexico geolocations. COI sequences showed low variability, with p-distances ranging from 0.18% to 0.92% (corresponding to 1-5 nucleotide differences across 544 base pairs), consistent with the presence of a single species. Scanning electron microscopy of the cestode larva revealed aristate gladiate spinitriches and capilliform filitriches within the acetabula, and capilliform filitriches on the scolex peduncle. Histopathological analysis of nodular lesions showed clusters of multiple larvae, predominantly located within the caecal lumen. Host tissues exhibited localised mucosal alterations, characterised by elements of mucosal atrophy, villus compression and epithelial degeneration. These changes were primarily the result of mechanical pressure exerted by the larvae within the caecal lumen. A focal accumulation of mucous cells (presumptive goblet cells) was observed in affected areas. While primary structural alterations were confined to the mucosa, inflammatory infiltration within the submucosa appeared minimal. Despite this typical localised tissue response, S. aurita appears to be a regular second intermediate host, whereas other clupeids may also act as second intermediate hosts and clupeid-feeding teleosts as paratenic hosts. This finding extends the distribution of Anthobothrium sp. 1 from the western Atlantic to the western Mediterranean Sea, where the definitive host remains unknown.</p>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":" ","pages":"e70267"},"PeriodicalIF":2.3,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148669742","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":"Deep Learning-Based Method for Damage Severity Grading of Black Shell Disease in Hong Kong Oyster (Crassostrea hongkongensis) Caused by Polydora Complex","authors":"Yuxiang Wang,&nbsp;Shengli Fu,&nbsp;Jingyue Zhang,&nbsp;Tuo Yao,&nbsp;Jie Lu,&nbsp;Haoyi Jiang,&nbsp;Jiadong Li,&nbsp;Lingtong Ye","doi":"10.1111/jfd.70170","DOIUrl":"10.1111/jfd.70170","url":null,"abstract":"<div>\u0000 \u0000 <p>The <i>Polydora</i> complex is a globally widespread polychaete parasite known for secreting acidic substances to bore tunnels into oyster shells. This process leads to the formation of dark brown crusts on the inner shell surface, a condition commonly referred to as “black shell disease”. Not only does this disease degrade the quality of shellfish, but it also causes substantial mortalities, with the Hong Kong oyster (<i>Crassostrea hongkongensis</i>) being one of its primary hosts. In this study, an improved Deeplabv3+ semantic segmentation model integrated with an attention mechanism was developed to identify and classify the severity of <i>Polydora</i>-induced disease in oysters. First, through systematic data collection and enhancement techniques, a comprehensive dataset of 4590 shellfish disease images was constructed, fully meeting the training requirements of convolutional neural networks (CNNs). Second, transfer learning was employed by leveraging pre-trained model weights, which validated the suitability of the self-constructed dataset for model training. Comparative analysis of multiple segmentation models confirmed Deeplabv3+ as the optimal baseline, achieving a mean Intersection over Union (MioU) of 88.76% and an average precision of 94%. To further enhance performance, the Deeplabv3+ model was upgraded by incorporating the Convolutional Block Attention Module (CBAM), a dual-module mechanism integrating channel and spatial attention. Compared to the original model, the improved version exhibited significant performance gains: MioU increased by 1.19%, average precision rose by 1.78%, and mFscore improved by 0.68%. Finally, an efficient and user-friendly web-based system was designed for grading and identifying <i>Polydora</i> disease severity. This system can accurately segment the diseased regions on the inner oyster shell, calculate their proportion relative to the total inner shell area, and precisely grade the disease severity, thereby providing robust technical support for the monitoring and prevention of oyster black shell disease.</p>\u0000 </div>","PeriodicalId":15849,"journal":{"name":"Journal of fish diseases","volume":"49 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147521089","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}