Journal of fish diseases最新文献

The Adriatic sturgeon, Acipenser naccarii, is an endemic species to the Adriatic Sea basin classified as critically endangered according to the IUCN Red List. Limited information is available regarding the health status and diseases affecting this species, particularly in the wild. In September 2023, a post-spawning female Adriatic sturgeon was found along the edges of the Adige River. The fish displayed abnormal swimming, cutaneous haemorrhages, extreme emaciation and died shortly after its finding. At necropsy, the stomach appeared enlarged with a firm texture and a severe restriction of the lumen due to the thickening of the gastric wall. A gastric leiomyoma was characterised by histology, and this represents the first description of such neoplasia in A. naccarii. In the intestine, a severe infestation with roundworm belonging to the phylum Acanthocephala was responsible for severe haemorrhagic enteritis. The parasites were identified as belonging to the species Leptorhynchoides polycristatus, providing the first description of such a parasite in Italy. Finally, genetic analyses were performed in order to assess genetic purity and relatedness with captive breeding stocks. The results showed that the individual did not cluster with any captive identified groups, supporting the likelihood of a pure and wild-origin Adriatic sturgeon.

Information on pharmacokinetics (PK) and tissue residues is critical for responsible drug use. The present study aimed to investigate PK characteristics and tissue distribution of florfenicol (FF) in Pacific white shrimp following a single dose of 150 mg/kg administered via oral gavage and medicated feed. Tissue depletion study and withdrawal time determination were performed after FF-medicated feed administration at a dosage of 150 mg/kg/day for 10 days. Furthermore, the effectiveness of FF against shrimp pathogens, Vibrio spp., was tested in vitro and in vivo, using broth microdilution technique and bacterial challenge experiment (immersion with Vibrio parahaemolyticus 10⁵ CFU/mL), respectively. Following the oral gavage, the peak concentration (C_max) in hemolymph was 162.81 μg/mL (at 0.14 h), and the area under the concentration-time curve (AUC) was 71.44 h·μg/mL, whereas those of the medicated feed method were much lower, being 6.84 μg/mL (at 0.40 h) and 8.25 h·μg/mL, respectively. The elimination half-lives (t_1/2β) of the two routes were very short and comparable, being 0.77 and 0.75 h, respectively. The hemolymph protein binding was 10.42%. FF was well distributed to the muscle, producing an AUC comparable to that of the hemolymph, but it was depleted at a slower rate. Drug residue was not found in the hemolymph and muscle at 24 h after the 10-day multiple dosing. The extremely fast drug elimination renders it practically ineffective in treating vibriosis in shrimp, despite demonstrating high efficacy against Vibrio spp. in vitro. Consequently, FF may not be an ideal treatment option for Vibrio spp. infections in shrimp aquaculture.

Infection with salmon gill poxvirus (SGPV) can cause severe gill pathology, leading to respiratory distress and high mortality rates in salmon hatcheries, known as salmon gill poxvirus disease. While the infection has been documented in salmon at sea, broodfish and wild salmon, its occurrence in salmon alevins remains unreported. This study presents four trials aiming to infect salmon alevins with SGPV, focusing on variations in storage conditions, processing of the infectious material and cohabitation. Utilising RNAscope in situ hybridisation and PCR techniques, we show that epithelial cells in the gills, oral cavity and skin of Atlantic salmon alevins can indeed be infected with SGPV. Moreover, our findings revealed that storing the challenge material at - 20°C compromises the virus infectivity. In contrast, preservation at - 80°C retains infectivity, even in the supernatant of homogenised infected gills.

Largely unpredictable, gelatinous plankton blooms are a growing concern for the ever-expanding mariculture industry. Recently, a bloom of a colonial hydrozoan known as Apolemia sp. was detected via a citizen-science initiative, Nye.dugnadforhavet.no, in mid-Norway in July 2023. By November 2023, the bloom spanned the entire 2500 km Norwegian coast, adversely impacting the aquaculture industry nationwide. This report describes the clinical presentation and pathology on farmed Atlantic salmon (Salmo salar) caused by an unprecedented bloom of Apolemia sp. at the Austevoll station of the Institute of Marine Research in Norway. Shortly after the Apolemia sp. arrived, many fish showed impaired swimming capacity and erratic behaviour. Over the following days, several fish displayed wounds on their eyes and skin, while daily mortality in some cages exceeded 17%. Histopathological analyses on moribund fish revealed acute gill damage and secondary complications, including necrosis and bacterial infections, in addition to ongoing amoebic gill disease (AGD). Blood biomarker profiles indicated severe physiological stress and organ dysfunction. Ultimately, all affected fish on site were euthanized due to welfare concerns, as was also the case for several other Norwegian salmon farms. This underscores the necessity for enhanced monitoring and mitigation strategies to protect farmed fish from such harmful events. The events of 2023 in Norway highlight the vulnerability of aquaculture to gelatinous plankton blooms and the necessity for research and innovation to develop effective monitoring and management practices.

Tenacibaculum dicentrarchi emerged as a major pathogen in Chilean salmon farming in early 2023, causing 32.9% of Atlantic salmon (Salmo salar) mortalities. Although recent studies have provided valuable insights into T. dicentrarchi through virulence mechanisms and genome analysis, genetic diversity based on the O-antigen gene cluster remains largely unexplored. In this study, we conducted a comparative genomic analysis of O-antigen biosynthesis genes in 30 whole-genome sequenced strains, including the T. dicentrarchi type strain. The analysis identified a single O-antigen gene cluster (O-AGC) consisting of 20 genes involved in the biosynthesis of this component of the lipopolysaccharide layer. Variations in the O-AGC revealed antigenic diversity within the species, allowing classification into four distinct groups, designated Types 1 to 4. Based on these findings, we developed a multiplex PCR-based genotyping scheme, which was successfully applied to 25 bacterial isolates from Chilean fish farms. Most isolates were identified as Type 1 and 3, while Types 2 and 4 were less common, with the same number of isolates. We also investigated whether core genome phylogeny correlated with O-AGC Types by including publicly available genomes from Chile, Norway and Canada. Notably, T. dicentrarchi isolates clustered into two groups: one comprising isolates from Norway and Canada, all belonging to Type 1. Another group consisted of Chilean isolates with diverse O-AGC Types (i.e., 1, 2, 3 and 4), including the type strain. This multiplex PCR approach provided a valuable tool for rapid and reliable typing of T. dicentrarchi, facilitating epidemiological studies and aiding in the selection of appropriate isolates for the vaccine development against tenacibaculosis in fish farms.

Piscine lactococcosis, caused by Lactococcus garvieae, has traditionally been reported in rainbow trout and marine fish in specific regions. However, its first outbreak in farmed gilthead seabream Sparus aurata in the northern Tyrrhenian Sea marks a significant expansion in the distribution of the disease. In 2024, a total of 212 gilthead seabream from three different aquaculture facilities, including one offshore farm with floating cages and two land-based tank farms, were subjected to diagnostic exams during mortality outbreaks. Bacterial isolation and molecular identification confirmed L. garvieae in market-size gilthead seabream collected during mortality outbreaks in the warm season or at seawater temperatures > 18°C. Our results highlight the importance of environmental monitoring and pathogen management in preventing piscine lactococcosis. The outbreaks align with previous studies on L. garvieae infections in marine fish, particularly regarding water temperature. The expanding geographic range of the pathogen necessitates further investigation into its ecology, particularly in Mediterranean aquaculture. This study highlights the need for improved biosecurity measures, early detection methods, and tailored vaccination strategies to mitigate the impact of piscine lactococcosis in gilthead seabream farming. Future research should focus on understanding the environmental triggers and host-pathogen interactions to develop more effective control strategies.

The description of skeletal disorders is commonly reported in fish species raised through aquaculture; however, wild marine fish may also exhibit high frequencies of anomalies, particularly the development of hyperostosis, a condition that causes thickening of the bones. Specimens of Oligoplites saliens (n = 15) and Oligoplites palometa (n = 14) were radiographed to verify hyperostotic bone occurrences. Hyperostosis was detected in all individuals (> 400 mm TL) analysed for both species, occurring in six distinct regions of the skeleton (supraoccipital bone, cleithrum, dorsal pterygiophores, anal pterygiophore, haemal spines, and neural spines), regardless of the sex of the individuals. No hyperostosis was found in the neural and haemal spines of O. palometa and in the anal pterygiophore of O. saliens. Histological sections of the supraoccipital bone of O. saliens were conducted, revealing high porosity characterised by the presence of vascular channels in bones with hyperostosis. The species exhibited species-specific patterns for the condition, demonstrating differences even among species of the same genus occurring in the same geographic area. This is the first record of hyperostosis for both species in Brazilian waters.

The objective of this study was to investigate the pharmacokinetic (PK) properties of oxolinic acid (OA) in black rockfish (Sebastes schlegelii) following a single oral administration of 30 mg/kg at 13°C and 22°C. Serum and tissue (muscle, liver and kidney) samples were collected at pre-determined time points and analysed using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The results demonstrated that temperature significantly influenced the PK parameters of OA. The terminal half-life (t_1/2λz) was prolonged at 22°C across all tissues, while the total body clearance (CL/F) was reduced, suggesting a slower drug elimination at higher temperatures. The peak concentration (C_max) and the area under the concentration-time curve (AUC) values increased with temperature, indicating enhanced systemic exposure at 22°C. The volume of distribution (Vz/F) decreased from 13°C to 22°C, indicating reduced tissue distribution of OA at the higher temperature. PK/pharmacodynamic (PK/PD) analysis revealed that a single oral dose of 30 mg/kg was insufficient to achieve optimal antibacterial efficacy, implying that higher doses may be necessary. These findings highlight the necessity of temperature-adjusted dosing strategies for OA treatment in black rockfish aquaculture to optimise therapeutic efficacy while minimising antimicrobial resistance risks.