Journal of aquatic animal health最新文献

{"title":"Evaluating functional effects of dietary phytogenic product supplementation in Nile Tilapia through performance, immunity, gene expression, and resistance to Flavobacterium oreochromis.","authors":"Ishini A Appuhami, Krishna Pada Singha, D Allen Davis, Brent M Vuglar, Fernando Y Yamamoto, Mark Farmer, Timothy J Bruce","doi":"10.1093/jahafs/vsag014","DOIUrl":"https://doi.org/10.1093/jahafs/vsag014","url":null,"abstract":"<p><strong>Objective: </strong>Phytogenics, which are plant-derived compounds, are increasingly gaining importance in aquaculture as sustainable and natural feed additives that support the performance and health of cultured fish. The current study evaluated the effects of dietary phytogenic supplementation in Nile Tilapia Oreochromis niloticus and the influence of phytogenics on growth, immunity, and resistance against Flavobacterium oreochromis.</p><p><strong>Methods: </strong>Fish were fed six experimental diets, including a control diet and five commercial phytogenic treatments-Syrena Boost (SY), Actifor Pro, Actifor Power (APO), Enviro QS, and Fresta Protect-for 60 d in a -recirculating aquaculture system. These products included bioactive compounds, such as saponins, thymol, essential oils, and condensed tannins. At the end of the trial, fish were sampled and blood was collected for serum lysozyme and biochemistry analyses, while spleen and head kidney were collected for immune gene expression analysis. After sampling, fish were challenged with F. oreochromis to evaluate resistance.</p><p><strong>Results: </strong>No significant differences in growth performance or nutrient utilization were observed among dietary treatments compared with the control. However, fish that were fed with phytogenic diets exhibited enhanced innate immune responses, as indicated by increased serum lysozyme activity in the APO treatment group (mean ± SE = 17.8 ± 0.76 μg/mL) and elevated serum albumin in the SY and Actifor Pro treatment groups. Although no significant differences were found in the expression of immune-related genes (interleukin-1 beta, interleukin-6, interleukin-8, and tumor necrosis factor alpha), multivariate analysis revealed tissue-specific and diet-dependent immune patterns. During the bacterial challenge with F. oreochromis, all phytogenic treatments resulted in a significantly higher survival compared with the control group, with fish in the SY (∼58%) and APO (∼51%) treatment groups showing the lowest cumulative mortality.</p><p><strong>Conclusions: </strong>These findings indicate that phytogenic compounds could enhance resistance to F. oreochromis in Nile Tilapia through modulating the innate immune response. Overall, among the five commercial phytogenics evaluated in this study, SY and APO showed the most potential as functional feed additives to improve Nile Tilapia immunity and resistance to columnaris disease.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148880531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 Citrobacter freundii as a disease-causing agent in Singhi Heteropneustes fossilis: A first report.","authors":"Lija Ghosh, C Laltlanmawia, Himadri Saha","doi":"10.1093/jahafs/vsag006","DOIUrl":"10.1093/jahafs/vsag006","url":null,"abstract":"<p><strong>Objective: </strong>The purpose of this study was to identify and describe Citrobacter freundii, which was associated with a disease outbreak in Singhi (also known as Stinging Catfish) Heteropneustes fossilis that are cultured under intensive freshwater farming conditions in Tripura, India, and to evaluate its pathogenicity and antimicrobial resistance profile.</p><p><strong>Methods: </strong>A bacterial isolate (COF_AHE25; GenBank accession no. ON798627) was recovered from diseased fish that were exhibiting white patches, skin ulcers, hemorrhages, fin rot, and mortality. The isolate was identified using phenotypic and biochemical evaluation, followed by molecular confirmation based on 16S ribosomal RNA gene sequencing and phylogenetic analysis. Pathogenicity was assessed through experimental infection trials, -daily monitoring of cumulative mortality, and estimation of the median lethal dose for the species. Host responses were evaluated through hematological, biochemical, and immunological analyses. Antimicrobial susceptibility was determined using the Kirby-Bauer disk diffusion method in accordance with the Clinical and Laboratory Standards Institute guidelines.</p><p><strong>Results: </strong>Experimental infection confirmed the virulence of the isolate, with infected Singhi developing clinical signs that were comparable to those observed during the natural outbreak. Mortality commenced at 4 d postinfection and progressed in a dose-dependent manner. Significant alterations in hematological, biochemical, and immunological parameters were observed, consistent with systemic bacterial septicemia. The median lethal dose of C. freundii strain COF_AHE25 was estimated at 2.5 × 107 CFU/fish. The isolate exhibited multidrug resistance, including resistance to tetracycline and erythromycin as well as to β-lactam antibiotics (penicillin, oxacillin, and cefoxitin) and vancomycin.</p><p><strong>Conclusions: </strong>The findings establish C. freundii as a pathogenic bacterium capable of causing significant disease and mortality in intensively farmed Singhi. The detection of resistance to antimicrobials commonly used in freshwater aquaculture highlights the need for strengthened disease surveillance, responsible antimicrobial stewardship, and improved health management practices in intensive fish farming systems.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"154-168"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148421348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Passive immunization with anti-virulent Aeromonas hydrophila whole serum protects Channel Catfish against motile Aeromonas septicemia.","authors":"Allison L Wise, Benjamin H Beck, Troy J Bader, Benjamin R LaFrentz, Priscilla C Barger, Craig A Shoemaker","doi":"10.1093/jahafs/vsag009","DOIUrl":"10.1093/jahafs/vsag009","url":null,"abstract":"<p><strong>Objective: </strong>Recently, we demonstrated the efficacy of oral bacterin virulent Aeromonas hydrophila (vAh) vaccines (S14-452 and ML09-119) in Channel Catfish Ictalurus punctatus, but gaps in knowledge exist with respect to protective immunity induced by vAh bacterins. Specific antibodies were proposed as a potential mechanism of protection; thus, the aim of the study was to assess whether passive immunization with anti-vAh whole serum provides protection upon vAh challenge.</p><p><strong>Methods: </strong>The protective role of anti-vAh whole serum was determined by passive immunization of Channel Catfish, followed by vAh challenge. Antiserum was generated by active immunization of Channel Catfish with three inactivated vAh strains (ALG-15-097, S14-452, and ML09-119). Thereafter, antibody presence was confirmed and quantified via enzyme-linked immunosorbent assay. Three replicated passive immunization experiments were completed using 15-g Channel Catfish with various treatment groups, including control sera, heat-inactivated control sera, anti-vAh sera, heat-inactivated anti-vAh sera, and fetal bovine serum. A western blot analysis was conducted postchallenge to determine whether antibodies generated against one isolate of vAh cross-reacted with antigens of other vAh isolates and a typical A. hydrophila strain, thus providing insights into the cross-protective nature of the vaccine.</p><p><strong>Results: </strong>All fish immunized with anti-vAh serum or heat-inactivated anti-vAh serum demonstrated 100% protection and cross-protection upon vAh challenge. Fish that were passively immunized with control serum, heat-inactivated control serum, or fetal bovine serum exhibited 30-50% survival depending on the experiment. The antiserum exhibited antibodies that cross-reacted with some proteins and the lipopolysaccharide of the homologous and heterologous isolates, including a typical A. hydrophila isolate.</p><p><strong>Conclusions: </strong>Passive immunization with anti-vAh sera provided 100% protection in all trials, demonstrating strong and consistent efficacy even at reduced antibody levels. Despite variability caused by heat inactivation, complete protection was maintained, highlighting the potency of the antiserum. Survival outcomes and western blot cross-reactivity further supported the protective and cross-protective capability of whole serum against diverse vAh strains. Collectively, these findings indicate that vAh-derived antibodies are key mediators of protection. Our findings point to mechanisms of immunity against vAh and guide vaccine development, ultimately preventing large-scale mortalities caused by vAh.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"169-180"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148421330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing a semi-validated quantitative PCR for high-throughput surveillance of Ichthyophonus sp. in Yukon River Chinook Salmon.","authors":"Jayde A Ferguson, Davis J Stewart, Franklin R Woitel, Toshihide Hamazaki, Paul Hershberger, Makayla Stewart, Zoe Munson, Zachary Liller","doi":"10.1093/jahafs/vsag010","DOIUrl":"10.1093/jahafs/vsag010","url":null,"abstract":"<p><strong>Objective: </strong>We sought to determine the suitability of a semi-validated quantitative PCR (qPCR) assay for assessing the prevalence and density of Ichthyophonus sp. infections in Yukon River Chinook Salmon Oncorhynchus tshawytscha, representing a new species and location for the assay's application. Ichthyophonus sp. causes severe disease that has been implicated in the en route prespawning mortality of this Chinook Salmon stock. The reduced survival of these fish has caused many hardships for the people who rely on them.</p><p><strong>Methods: </strong>We assessed a modified qPCR assay with stage 1 and partial stage 2 validation per World Organisation for Animal Health criteria for Ichthyophonus sp. surveillance in Yukon River Chinook Salmon. Cohen's kappa tests were used to compare qPCR results of infection status (infected/uninfected) with those of explant culture-the current reference standard. Linear regressions were used to interrogate qPCR results of parasite gene copies per milligram for infection density with parasite counts per cubic millimeter from the reference standard of histopathology.</p><p><strong>Results: </strong>We found that the prevalence of Ichthyophonus sp. DNA by qPCR did not significantly differ from that of the reference standard for explant culture of the parasite. The qPCR demonstrated high analytical sensitivity and estimated diagnostic performance. Gene copies per milligram by qPCR were correlated to the number of schizonts per cubic millimeter with an R2 value of 0.40-0.41, but the R2 increased to 0.92 after we accounted for parasite size in the 2023-2024 data set.</p><p><strong>Conclusions: </strong>The results from this qPCR with our modifications were equivalent to the prevalences and densities determined by reference standards and fit our purpose for a rapid Ichthyophonus sp. surveillance assay. This could be used in-season to inform fishery managers about disease and mortality associated with Ichthyophonus sp. infections in high-risk regions like the Yukon River, where en route prespawning mortality associated with this parasite occurs periodically.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"181-196"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148591558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New culture medium enhances the isolation and culture of Flavobacterium psychrophilum, causative agent of bacterial coldwater disease and Rainbow Trout fry syndrome.","authors":"Christopher Knupp, Sean M G Lennox, Esteban Soto, Gregory D Wiens, Thomas P Loch","doi":"10.1093/jahafs/vsag011","DOIUrl":"10.1093/jahafs/vsag011","url":null,"abstract":"<p><strong>Objective: </strong>Flavobacterium psychrophilum causes bacterial coldwater disease (BCWD) and Rainbow Trout fry syndrome (RTFS) in salmonids, resulting in significant economic losses worldwide. Bacterial culture remains a widely used method for F. psychrophilum diagnostics and is core to BCWD and RTFS research; however, some isolates grow poorly on existing media. The primary goal of this study was to develop a solid culture medium that improves the in vitro recovery of F. psychrophilum across a diverse set of multilocus sequence typing variants.</p><p><strong>Methods: </strong>Initially, CFU yields of 165 diverse F. psychrophilum isolates were compared across three established media, and the best-performing medium was selected for optimization. A Plackett-Burman screening design was used to identify influential medium components, after which two new media (F. psychrophilum medium-A [FPM-A] and F. psychrophilum medium-B [FPM-B]) were formulated and compared with tryptone yeast extract salts medium (TYES) under laboratory and field conditions.</p><p><strong>Results: </strong>Five medium components (e.g., casamino acids, CaCl2, MgSO4, tryptose, and fetal bovine serum) significantly influenced CFU yield, guiding the formulation of FPM-A and FPM-B, which increased CFU yield by over 2.4-fold relative to TYES. During surveillance of 240 spawning-age salmonids (four species, four sites), FPM-A and FPM-B significantly improved F. psychrophilum recovery in comparison with TYES.</p><p><strong>Conclusions: </strong>The new media improved the recovery of diverse F. psychrophilum variants and improved culture-based detection from naturally infected fish. Both FPM-A and FPM-B performed similarly; however, FPM-A has fewer components, is less expensive to produce, and thus is recommended to support future BCWD/RTFS diagnostic and research efforts.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"197-213"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148584447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of a low-lipid diet on the gut microbiome and head kidney transcriptome of juvenile Chinook Salmon.","authors":"Claire E Couch, Konstantin Divilov, Crystal L Herron, Bing Wang, Olivia M Hakanson, Michelle M Scanlan, Luke D Whitman, Melanie J Davis, Carl B Schreck, James T Peterson","doi":"10.1093/jahafs/vsag004","DOIUrl":"10.1093/jahafs/vsag004","url":null,"abstract":"<p><strong>Objective: </strong>Pacific salmon Oncorhynchus spp. reared in production hatcheries are typically fed high-lipid, energy-dense diets to achieve large size and high body condition prior to release. In contrast, juveniles in natural environments tend to consume low-lipid, high-protein diets, and fish reared for research or conservation purposes are sometimes fed diets that are formulated to mimic natural diets and promote wild-like phenotypes. Understanding how these alternative diets affect fish health beyond growth and body condition could ultimately contribute to improving hatchery fish fitness.</p><p><strong>Methods: </strong>In this work, we evaluated changes in the fecal microbiome and gene expression of juvenile Chinook Salmon O. tshawytscha on a standard high-lipid hatchery diet versus a low-lipid diet formulated to mimic the nutrition profile of natural-origin fish. To evaluate the time scale at which diet alters the fecal microbiome, we collected longitudinal samples over a 12-week period and switched the diets of a subset of fish twice during the experiment. We used 16S ribosomal RNA gene amplicon sequencing to characterize fecal microbiome differences between fish on the two diets as well as hatchery-reared fish at a production hatchery, hatchery fish that had been captured after release into a stream, and natural-origin, stream-reared fish of similar ages. Additionally, we conducted RNA sequencing on head kidney samples from laboratory-reared fish to evaluate changes in gene expression in this important immune organ.</p><p><strong>Results: </strong>We found that the low-lipid diet and the hatchery diet resulted in microbiomes that differed from the microbiome of natural-origin fish and from each other and that diet-driven changes to the microbiome could occur in under 14 d. The low-lipid diet did not result in a microbiome that resembled the microbiome of naturally produced fish. Instead, the low-lipid diet resulted in a microbiome community that was distinct from those of fish reared on the hatchery diet and fish sampled from the wild. The RNA sequencing results indicated differential enrichment of pathways related to immunity, metabolism, and hormone synthesis between fish that were fed the two experimental diets.</p><p><strong>Conclusions: </strong>The results suggest that additional environmental factors influence the microbiome more strongly than diet formulation or that the low-lipid diet has a smaller effect on the microbiome than a natural, -invertebrate-based diet. Given that the gut microbiome and systemic immune function contribute significantly to disease resistance, our findings highlight the importance of understanding how diets fed to fish in captivity may affect fish health beyond growth and body condition metrics.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"118-134"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148430516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 characterization of Bacillus altitudinis JSHY-074: A potential probiotic candidate with antagonistic activity against highly lethal Vibrio parahaemolyticus.","authors":"Xiaotong Wang, Ge Jiang, Jie Cheng, Yi Qiao, Xiaohui Cao, Xianping Fan, Kuipeng Fu, Qingguo Meng, Hui Shen","doi":"10.1093/jahafs/vsag005","DOIUrl":"10.1093/jahafs/vsag005","url":null,"abstract":"<p><strong>Objective: </strong>The highly lethal Vibrio disease (HLVD) caused by highly lethal Vibrio parahaemolyticus (VpHLVD) represents a significant threat to Pacific white shrimp Litopenaeus vannamei aquaculture. The existing disease control approaches often rely on antibiotics, leading to drug resistance and environmental pollution, thereby limiting the sustainable development of shrimp farming. Probiotics are recognized for their ability to enhance host disease resistance and to inhibit pathogenic bacteria with high safety and environmental friendliness.</p><p><strong>Methods: </strong>We evaluated the potential of a probiotic bacterial dietary supplement for HLVD prevention. Bacillus altitudinis strain JSHY-074, isolated from coastal aquaculture environments in Jiangsu, China, was identified based on morphological characterization, 16S ribosomal DNA sequencing, and whole-genome analysis. Its antagonistic activity against V. parahaemolyticus strain SHY1669 was determined by co-culture inhibition tests, and the probiotic effect was verified through a VpHLVD challenge experiment on Pacific white shrimp fed with JSHY-074.</p><p><strong>Results: </strong>The strain JSHY-074 exhibited potent antagonistic activity against V. parahaemolyticus strain SHY1669, with inhibition zones expanding from 12 ± 0.31 mm (mean ± SD) at 6 h of co-culture to 30 ± 0.84 mm at 96 h of co-culture. At an inoculum density of 1.0 × 108 CFU/mL, the inhibition rate reached 88.58% at 72 h. Whole--genome analysis revealed nine gene clusters associated with secondary metabolite production, with lichenysin preliminarily identified as the primary active compound. The VpHLVD challenge experiment demonstrated that feeding Pacific white shrimp with strain JSHY-074 achieved a 70% survival rate within 5 d and a 5,942-fold reduction in hepatopancreas pathogen load (from 6.12 × 107 to 1.03 × 104 copies/ng).</p><p><strong>Conclusions: </strong>This is the first report of B. altitudinis exhibiting antagonistic activity against VpHLVD. The high technological readiness level of B. altitudinis JSHY-074 makes it a versatile probiotic feed additive, and its safety and effectiveness make it well suited for fast deployment and use in shrimp farming, offering a nutritional approach to reducing antibiotic dependency and promoting sustainable aquaculture practices.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"135-153"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148199148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Susceptibility of Nile Tilapia Oreochromis niloticus fingerlings to different Lactococcus petauri genotypes isolated in the USA.","authors":"Yoandy Coca, Zeinab Yazdi, Eileen Henderson, Haitham H Mohammed, Taylor I Heckman, Matt J Griffin, Esteban Soto","doi":"10.1093/jahafs/vsag008","DOIUrl":"10.1093/jahafs/vsag008","url":null,"abstract":"<p><strong>Objective: </strong>In this study, the pathogenicity of two genetically distinct Lactococcus petauri strains, one isolated from catfish Ictalurus spp. in Alabama, USA, belonging to sequence type 142, and one from Rainbow Trout Oncorhynchus mykiss in California, USA, belonging to sequence type 145, were evaluated in experimental challenges using a Nile Tilapia Oreochromis niloticus fingerling infection model.</p><p><strong>Methods: </strong>Since tilapia can be cultured at a wide range of temperatures in vivo, experiments were conducted at 25 ± 2°C and 30 ± 2°C. The fish were challenged via intracoelomic injection of ∼107 CFU/fish or by immersion in 5 L of water containing ∼107 CFU/mL for 1 h. Morbidity and mortality were monitored twice daily for 3 weeks. Water samples from each tank were collected at 6 h and at 1, 9, and 15 d postchallenge to evaluate L. petauri DNA load using a species-specific quantitative PCR.</p><p><strong>Results: </strong>No significant morbidity or mortality was observed in any of the treatment groups during the challenge. At the end of the 3 weeks, all of the fish were euthanized and brain samples from 10 fish per group were cultured on nutrient agar to evaluate the bacterial persistence in the survivors. None of the surviving fish yielded positive isolation of L. petauri. Additionally, no significant histopathological changes were observed between the control and challenged tilapia. Bacterial DNA in the water was detected only at 6 h and at 1 d postchallenge in some treatments.</p><p><strong>Conclusions: </strong>These findings suggest that under the conditions that were tested, the two strains of L. petauri that were evaluated appear of low virulence to Nile Tilapia.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"214-221"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148455855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transcriptional changes in wild Yukon River Chinook Salmon associated with Ichthyophonus infections.","authors":"Lizabeth Bowen, Vanessa R von Biela, Jayde A Ferguson, Shannon C Waters, Amy M Regish, Michael P Carey, Zachary Liller, Morag Clinton, Paul K Hershberger, Christian E Zimmerman","doi":"10.1093/jahafs/vsag007","DOIUrl":"10.1093/jahafs/vsag007","url":null,"abstract":"<p><strong>Objective: </strong>We compared differentially expressed genes in Chinook Salmon Oncorhynchus tshawytscha with three divergent Ichthyophonus statuses (undetected, subclinical infections, or clinical disease; n = 100) to investigate associated transcriptomic responses. Disease associated with the fish parasite Ichthyophonus sp. was first diagnosed in adult Chinook Salmon from the Yukon River in the late 1980s and has subsequently been implicated in premature host mortality.</p><p><strong>Methods: </strong>Chinook Salmon tissue sample collections and Ichthyophonus infection data were leveraged from a multi-agency collaboration during summer 2022 at three locations along the main-stem Yukon River that spanned nearly 2,000 km of freshwater migration (lower, middle, and upper river). We sequenced the transcriptome and compared this to infection status based on routine diagnostic procedures.</p><p><strong>Results: </strong>Among the 17,569 genes for which messenger RNA was detected, we identified a transcription signature in the skeletal muscle that was associated with Ichthyophonus infections and included 53 differentially expressed genes. The differentially expressed genes and their pathways included those known for involvement in immune functions, energy synthesis, cellular breakdown, and reproduction-all processes that are known to be influenced by senescence during spawning migrations.</p><p><strong>Conclusions: </strong>Results demonstrate a clear transcriptional difference between diseased fish (clinical disease group) and those in which Ichthyophonus was undetected, including identifying candidate markers for infection in this population. These results provide a foundation for development of nonlethal biomarkers to evaluate potential Ichthyophonus infections in Chinook Salmon based on gene transcription, protein products, or gene variants (e.g., polymorphisms).</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"87-106"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148352013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 quantitative PCR detection methods and epidemiological investigation of ranavirus and megalocytivirus infections in hybrid snakehead (Northern Snakehead ♀ × Blotched Snakehead Channa maculata ♂).","authors":"Jiahao Zhang, Wenhao Wu, Caiyi Wen, Yanxin Sun, Biao Jiang, Youlu Su","doi":"10.1093/jahafs/vsaf002","DOIUrl":"10.1093/jahafs/vsaf002","url":null,"abstract":"<p><strong>Objective: </strong>In China, the incidence of iridovirus infections in economically valuable fish species is increasing, but there is a paucity of reports documenting ranavirus infections and there are no reports concerning megalocytivirus in hybrid snakehead (Northern Snakehead Channa argus ♀ × Blotched Snakehead C. maculata ♂).</p><p><strong>Methods: </strong>In this study, the major capsid protein DNA fragments of two iridoviruses were amplified from diseased hybrid snakehead, and two specific primers and TaqMan probes were designed based on the conserved sequences. Using the constructed recombinant plasmid as the standard for real-time fluorescent quantitative PCR, two real-time TaqMan quantitative detection methods for the iridoviruses were established, and the sensitivity, repeatability, and specificity of these two methods were evaluated.</p><p><strong>Results: </strong>The standard curves for both methods exhibited strong linear correlations (R2 > 0.99), with slopes of -3.28 and -3.231, respectively, and the detection limits were 28 and 27 viral genome copies, which were 100 times more sensitive than conventional PCR. Applying these methods to 272 hybrid snakehead, we found an average positive rate of 9.93% (27/272) for ranavirus and 3.31% (9/272) for megalocytivirus. During the breeding stage (parental generation and fry), megalocytivirus was detected at a rate of 2.67% (2/75), while ranavirus was absent. However, ranavirus was present from April to November during the cultivation stage, and megalocytivirus was primarily detected in July and August. Fry up to 10 cm in length were most susceptible to both viruses, but no cross infections were detected.</p><p><strong>Conclusions: </strong>These findings offer valuable insights into the epidemiology of ranavirus and megalocytivirus in hybrid snakehead.</p>","PeriodicalId":15235,"journal":{"name":"Journal of aquatic animal health","volume":" ","pages":"107-117"},"PeriodicalIF":2.1,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148591603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}