Journal of fish diseases最新文献

Mucosal barriers are gatekeepers of health and exhibit homeostatic variation in relation to habitat and disease. Mucosal Mapping technology provides an in-depth examination of the dynamic mucous cells (MCs) in fish mucosal barriers on tangential sections, about 90° from the view of traditional histology. The method was originally developed and standardized in academia prior to the establishment of QuantiDoc AS to apply mucosal mapping, now trademarked as Veribarr™ for the analysis of skin, gills and gastrointestinal tracts. Veribarr™ uses design-based stereology for the selection and measurement of cell area (size) (μm²), the volumetric density of MCs in the epithelium (MCD, amount of the epithelia occupied by MCs, in %) and the calculated abundance of the MCs (barrier status or defence activity). MC production was mapped across the skin and gill epithelia in 12 species, discovering that gills consistently have two distinct groups of MCs, one on the lamellae where MCs are few and small and one on the filament where MCs are larger and more abundant. MCs were usually much larger in the skin than in the gills, with the latter requiring fewer and smaller cells for adequate respiration. The difference observed between MCs in gill lamella and gill filament is likely a result of functional demands. In addition, our findings also highlight a variation in the mucosal parameters between the species skin, which cannot be explained by the weight differences, and a potential link between MC distribution and species-specific lifestyles in the gill lamella. This diversity necessitates the development of species and tissue site-specific reference intervals for mucosal health evaluation. Mucosal bivariate reference intervals were developed for MC production, including size (trophy) and calculated defence activity (plasia) in the skin and gills of Atlantic salmon, to contrast new measurements against historical data patterns. The application of mucosal reference intervals demonstrates that stress from parasites and treatments can manifest as changes in mucosal architecture, as evidenced by MC hypertrophy and hyperplasia within the gill lamellae. These reference intervals also facilitate comparisons with wild Atlantic salmon, revealing a somewhat higher MC level in farmed salmon gill lamellae. These findings suggest that MC hyperplasia and hypertrophy in the gills are stress/environmental responses in aquaculture. They also advocate for developing specific mucosal bivariate homeostatic reference intervals in aquaculture to improve fish health and welfare across all farmed species.

Edwardsiella piscicida is an emerging bacterial pathogen and the aetiological agent of edwardsiellosis among cultured and wild fish species globally. The increased frequency of outbreaks of this Gram-negative, facultative intracellular pathogen pose not only a threat to the aquaculture industry but also a possible foodborne/waterborne public health risk due to the ill-defined zoonotic potential. Thus, understanding the role of temperature on the virulence of this emerging pathogen is essential for comprehending the pathogenesis of piscine edwardsiellosis in the context of current warming trends associated with climate change, as well as providing insight into its zoonotic potential. In this study, significant temperature-dependent alterations in bacterial growth patterns were observed, with bacterial isolates grown at 17°C displaying higher peak growth sizes, extended lag times, and slower maximal growth rates than isolates grown at 27or 37°C. When E. piscicida isolates were grown at 37°C compared to 27 and 17°C, mass spectrometry analysis of the E. piscicida proteome revealed significant downregulation of crucial virulence proteins, such as Type VI secretion system proteins and flagellar proteins. Although in vivo models of infection are warranted, this in vitro data suggests possible temperature-associated alterations in the virulence and pathogenic potential of E. piscicida in poikilotherms and homeotherms.

Atlantic salmon aquaculture companies in British Columbia (BC) must report fish health events to Fisheries and Oceans Canada (DFO) as part of their licensing conditions. Our study aimed to summarize these fish health events reported by Atlantic salmon sites in BC to identify spatial and spatio-temporal clusters. We conducted descriptive, retrospective global, and local cluster analyses using Moran's I and scan statistics. Between 2016 and 2022, 265 fish health events were reported. The annual incidence ranged from 5.60 (95% CI: 3.90–7.80) to 6.86 (95% CI: 4.70–9.60) health events per 100 active site-months. The most common events were yellow mouth (60.75%; 161/265) and salmonid rickettsial septicaemia (SRS) (15.47%; 41/265). The Moran's I index was positive and significant for yellow mouth, SRS, and overall fish health events at different distance bands. Most of the spatial and spatio-temporal clusters were identified in the west-central and southwestern parts of Vancouver Island. Our study hypothesizes that management practices, environmental conditions, and water quality parameters may have influenced the increased reporting of fish health events in these regions. Overall, the study highlights the potential of publicly available data for practical risk mapping in understanding the patterns of farmed Atlantic salmon diseases in BC.

Chinese rice-field eels rhabdovirus (CrERV) causes haemorrhagic disease in Chinese rice-field eels (Monopterus albus), leading to significant mortality and economic losses. Sensitive detection of CrERV nucleic acids is essential to control the spread of this pathogen and to treat infected individuals. Herein, we developed an efficient and sensitive droplet digital PCR (ddPCR) method to rapidly detect and quantify CrERV. The ddPCR assay optimal conditions were an annealing temperature of 53°C, and primer and probe concentrations of 0.5 and 0.25 μM, respectively. The assay had a diagnostic sensitivity of 0.23 copies/μL, and was highly specific, showing no cross reactivity with other viruses (infectious haematopoietic necrosis virus, grass carp reovirus, spring viremia of carp virus, largemouth bass ranavirus, carp edema virus, Chinese giant salamander iridovirus, and white spot syndrome virus). Real-time quantitative PCR testing of 30 Chinese rice-field eels samples detected CrERV in 7 samples (23.3%), whereas ddPCR detected CrERV in 12 samples (40%), demonstrating its higher sensitivity. Thus, ddPCR represents an advanced method to absolutely quantify CrERV in infected fish with low virus concentrations, providing a valuable tool to manage the spread and impact of CrERV.

This study provides a comprehensive summary of the findings regarding the application and diagnostic efficacy of droplet digital PCR (ddPCR) in detecting viral and bacterial pathogens in aquaculture. Utilizing a systematic search of four databases up to 6 November 2023, we identified studies where ddPCR was deployed for pathogen detection in aquaculture settings, adhering to Preferred Reporting Items for Systematic Reviews and Meta-analysis of Diagnostic Test Accuracy guidelines. From the collected data, 16 studies retrieved, seven were included in a meta-analysis, encompassing 1121 biological samples from various fish species. The detection limits reported ranged markedly from 0.07 to 34 copies/μL. A direct comparison of the diagnostic performance between ddPCR with quantitative PCR (qPCR) proved challenging due to limited data, thus only a pooled sensitivity analysis was feasible. The results showed a pooled sensitivity of 0.750 (95% confidence interval [CI]: 0.487–0.944) for ddPCR, compared to 0.461 (95% CI: 0.294–0.632) for qPCR, with no statistically significant difference in sensitivity between the two methods (p = .5884). Notably, significant heterogeneity was observed among the studies (I² = 93%–97%, p < .01), with the year of publication significantly influencing this heterogeneity (p < .001), but not the country of origin (p = .49). No publication bias was detected, and the studies generally exhibited a low risk of bias according to QUADAS-C criteria. While ddPCR and qPCR showed comparable sensitivities in pathogen detection, ddPCR's capability to precisely quantify pathogens without the need for standard curves highlights its potential utility. This characteristic could significantly enhance the accuracy and reliability of pathogen detection in aquaculture.

Giant freshwater prawn (Macrobrachium rosenbergii (MR)) is a significant aquafarm species commercially cultured in Taiwan. Intensive farming practices have led to the outbreak of Lactococcus garvieae (LG), which causes Lactococcosis in MR. Recently, LG has re-emerged and the number of mortalities in prawn farms has increased in Taiwan. However, there is no preventative strategy described and a lack of knowledge on virulence factors and pathogenesis from LG in MR. The most virulent strain of L. garvieae from M. rosenbergii was screened in vivo among seven isolates selected for infectivity testing injecting 0.1 mL of 10⁸ CFU/mL bacterial concentration. Among the seven isolates screened, L. garvieae 109-6 resulted in 100% mortality within 3 days post-infection. Furthermore, 109-6 L. garvieae LD₅₀ dosage from in MR was found to be 10⁶ CFU/mL. Subsequently, the most virulent strain 109-6 was sequenced using MinIon Nanopore sequencing. Results indicated that the LG genome yielded a protein-coding of 3857 with 59 tRNA and 16 rRNA and no plasmid. Interestingly, the distribution of subsystems in the annotated genome revealed genes related to virulence, defence, and disease among LG 50 genes. Altogether, the virulent strain and its genome data revealed distinctive features of LG, which hinted toward its pathogenicity and could facilitate for better preventive strategies.

Thyroid tissue in teleosts is located mainly in the pharyngeal region, usually reaching other adjacent anatomical locations. Herein, a nodular lesion located in the left operculum of a Senegal seabream (Diplodus bellottii) was surgically excised and sent for microscopical evaluation. Microscopically, the lesion presented irregular borders and consisted in columnar epithelial cells arranged in a tubulopapillary pattern, surrounding a central lumen filled with acellular, acidophilic and homogeneous, material (‘colloid’). To determine the lesion's histogenesis, immunohistochemistry was performed employing antibodies for AE1/AE3, CK7, thyroglobulin and vimentin. The neoplastic cells presented low mitotic index and positive immunolabelling for CK7 and thyroglobulin. Therefore, a diagnosis of ectopic thyroid adenoma was made. Herein, the successful employment of antibodies classically used in mammals for accurate diagnosis of thyroid disorders is described. Proliferation of thyroid tissue in fish may reflect environmental and physiological imbalances, making the study and correct diagnosis of these tumours in this species important.

Among the most important aquaculture resources for our country, salmon and trout stand out. Their production has increased significantly in recent decades, making them two of the most valuable resources in economic terms. However, high aquaculture production has allowed many pathogens to proliferate, causing infectious diseases and significant production losses. Piscirickettsia salmonis is a gram-negative, facultative intracellular bacterium that is responsible for causing severe disease in a variety of salmonid fish species. Despite the significant impact of P. salmonis on aquaculture, effective treatments for this disease remain limited. Current prevention and control strategies often include antibiotics and vaccines. However, these treatments have shown varying degrees of efficacy. A promising approach involves synthesizing bioactive analog compounds with antibacterial properties. Quinones, secondary metabolites that are abundant in nature, have become a focal point of interest due to their diverse physiological activities, including antibiotic, insecticidal, antifungal, and anticancer properties. In this study, it is shown the synthesis of series 6-bromo-7-arylaminoisoquinoline-5,8-quinones, the characterization of these compounds using classical spectroscopic methods such as one-dimensional nuclear magnetic resonance (NMR), FT-IR (infrared), mass spectrometry, and the biological activity against Piscirickettsia salmonis. The brominated derivative compounds showed no cytotoxicity at any concentration evaluated. Furthermore, the infectivity of P. salmonis after treatment with the analog compounds indicated that derivatives methyl 6-bromo-7-((4-methoxyphenyl)amino)-1,3-dimethy-5,8-dioxo-5,8-dihydroisoquinoline-4-carboxylate (4b) and methyl 7-((4′-amino-[1,1′-biphenyl]-4-yl)amino)-6-bromo-1,3-dimethy-5,8-dioxo-5,8-dihydroisoquinoline-4-carboxylate (4g) reduced the bacterial load at 25 μg/mL concentration.

The ability to impact the immune response of the host has been recognized as essential for the success of a virus during infection. A few groups of viruses can combine these immunomodulatory mechanisms with specific patterns of their own transcriptional and replication regulation to achieve persistence within the host long term. The Herpesvirales order is one of those groups and the resultant state is known as latency. Throughout the years, latency has been studied in many host-herpesvirus models to attempt to understand the complex and profound effects of this state on the host's systems, and in the hopes of deciphering a way to eliminate the latent state from survivors of the primary infection. Most studies of herpesvirus latency have been conducted on mammalian host species, but this review summarizes the data available regarding herpesviruses in fish species and their latent state. As the field of aquatic animal health research continues to advance, the elucidation of these complex mechanisms will be crucial for disease control, prevention, and treatment.