Diseased Fish Research Articles

Database construction and comparative genomics analysis of genes involved in nutritional metabolic diseases in fish

Nutritional metabolic diseases in fish frequently arise in the setting of intensive aquaculture. The etiology and pathogenesis of these conditions involve energy metabolic disorders influenced by both internal genetic factors and external environmental conditions. The exploration of genes associated with nutritional and metabolic disorder has sparked considerable interest within both the aquaculture scientific community and the industry. High-throughput sequencing technology offers researchers extensive genetic information. Effectively mining, analyzing, and securely storing this data is crucial, especially for advancing disease prevention and treatment strategies. Presently, the exploration and application of gene databases concerning nutritional and metabolic disorders in fish are at a nascent stag. Therefore, this study focused on the model organism zebrafish and five primary economic fish species as the subjects of investigation. Using information from KEGG, OMIM, and existing literature, a novel gene database associated with nutritional metabolic diseases in fish was meticulously constructed. This database encompassed 4583 genes for Danio rerio, 6287 for Cyprinus carpio, 3289 for Takifugu rubripes, 3548 for Larimichthys crocea, 3816 for Oreochromis niloticus, and 5708 for Oncorhynchus mykiss. Through a comparative systems biology approach, we discerned a relatively high conservation of genes linked to nutritional metabolic diseases across these fish species, with over 54.9 % of genes being conserved throughout all six species. Additionally, the analysis pinpointed the existence of 13 species-specific genes within the genomes of large yellow croaker, tilapia, and rainbow trout. These genes exhibit the potential to serve as novel candidate targets for addressing nutritional metabolic diseases.

Potential plasma biomarkers for the onset of heart and skeletal muscle inflammation from Piscine orthoreovirus-1 infection in Atlantic salmon (Salmo salar)

Biomarkers that give quantifiable information about disease development are valuable diagnostic indicators providing opportunities to thwart adverse outcomes through timely detection and initiation of countermeasures. Whereas human medicine already relies extensively on biomarker analysis, their application in the diagnostics of fish diseases is still at a tentative beginning. However, the increased utilisation of broad-range analytical approaches such as untargeted proteomics enhances the chances to discover changes in the levels of proteins, which are connected to fish health and could serve as novel biomarkers. In the present study, proteomic analysis accompanied by biostatistical data processing was employed with the aim of identifying plasma biomarker candidates for the onset of heart and skeletal muscle inflammation (HSMI) caused by Piscine orthoreovirus (PRV)-1 infection in Atlantic salmon. HSMI is a common viral disease and threat to fish welfare and productivity in Norwegian aquaculture, so that the early detection of HSMI development would allow a timely intervention to limit the damage. In the search for biomarker candidates, salmon plasma was sampled five and eight weeks after a PRV-1 cohabitation challenge experiment and from adequate control fish, and analysed by mass spectrometry-based proteomics. The proteome dataset contained 695 proteins with >90% probability of correct identification according to the set cut-off criteria for peptide quality. Time- and condition-related differences in protein abundance levels were revealed by multivariate analysis. Comparison of the proteins identified as significant using three different biostatistical models resulted in a short list of four potential biomarkers: galectin-3-binding protein (Gal-3BP), fucolectin-6, urokinase plasminogen activator surface receptor and ryanodine receptor 3. The physiological functions described for these proteins in mammals designate them as interesting indicators of inflammatory diseases also in other species, such as PRV-1 pathogenesis in salmon. In situ-hybridisation targeting Gal-3BP and PRV-1 mRNA in heart tissue sections from the same challenge trial showed a significant upregulation of Gal-3BP mRNA in infected salmon hearts as compared to controls, supporting the findings of the proteomic analysis and suggesting a role in the onset of heart- and skeletal muscle inflammation.

A Duplex PCR Assay for Rapid Detection of Klebsiella pneumoniae and Chryseobacterium in Large Yellow Croaker Fish.

Both Klebsiella pneumoniae and Chryseobacterium cause an increasing number of diseases in fish, resulting in great economic losses in aquaculture. In addition, the disease infected with Klebsiella pneumoniae or Chryseobacterium exhibited the similar clinical symptoms in aquatic animals. However, there is no effective means for the simultaneous detection of co-infection and discrimination them for these two pathogens. Here, we developed a duplex polymerase chain reaction (PCR) method based on the outer membrane protein A (ompA) gene of Klebsiella pneumoniae and Chryseobacterium. The specificity and validity of the designed primers were confirmed experimentally using simplex PCR. The expected amplicons for Klebsiella pneumoniae and Chryseobacterium had a size of 663 and 1404 bp, respectively. The optimal condition for duplex PCR were determined to encompass a primer concentration of 0.5 μM and annealing temperature of 57°C. This method was analytical specific with no amplification being observed from the genomic DNA of Escherichia coli, Vibrio harveyi, Pseudomonas plecoglossicida, Aeromonas hydrophila and Acinetobacter johnsonii. The limit of detection was estimated to be 20 fg of genomic DNA for Chryseobacterium and 200 fg for Klebsiella pneumoniae, or 100 colony-forming units (CFU) of bacterial cells in both cases. The duplex PCR was capable of simultaneously amplifying target fragments from genomic DNA extracted from the bacteria and fish liver. For practical validation of the method, 20 diseased fish were collected from farms, among which 4 samples were PCR-positive for Klebsiella pneumoniae and Chryseobacterium. The duplex PCR method developed here is time-saving, specific, convenient, and may prove to be an invaluable tool for molecular detection and epidemiological investigation of Klebsiella pneumoniae and Chryseobacterium in the field of aquaculture.

High-intensity exercise training in large yellow croaker is a compromise between disease resistance and fish welfare

Exercise training is being applied to improving the productivity and welfare of farmed fish species. Nonetheless, research into whether exercise training improves disease resistance and immune function in fish is still at an early stage, and more studies is required. This study examined the impact of exercise training on growth performance, disease resistance and immune function of large yellow croaker (Larimichthys crocea). Juvenile fish underwent a 12 days training regime at 2–3 BL.s−1, followed by a parasite disease challenge test (Cryptocaryon irritans). Fish muscle RNA-seq analyses was used to evaluate the influence of exercise on juvenile immune function. The results showed that: (1) exercising at 2–3 BL.s−1 had no impact on the growth of juvenile croakers, however it induced an inflammatory response in croakers, leading to increased mortality in the treatment group (T) compared to the control group (C); (2) exercising also enhanced the resistance of T to C. irritans, resulting in a significant 17.6% increase in the survival rate of T compared to that of C; and (3) the RNA-seq analysis of the muscles demonstrated that differentially expressed genes (DEGs) between T and C were primarily involved in regulating the expression of genes related to muscle development and immunity in croaker; (4) enrichment analyses using KEGG and GO revealed that the DEGs were significantly enriched in pathways related to metabolic processes and biosynthesis. In conclusion, it is suggested that exercise training with high water speed induces an inflammatory response in the large yellow croaker, compromising the welfare of the fish. However, this stimulates the expression of immune-regulation-related genes and pathways, thereby improving the disease resistance of exercising individuals. Our study reveals that exercise training can improve disease resistance of large yellow croaker, which has significant implications for the sustainability of the croaker aquaculture industry.

An aquaculture risk model to understand the causes and consequences of Atlantic Salmon mass mortality events: A review

AbstractMass mortality events (MMEs) are defined as the death of large numbers of fish over a short period of time. These events can result in catastrophic losses to the Atlantic salmon aquaculture industry and the local economy. However, they are challenging to understand because of their relative infrequency and the high number of potential factors involved. As a result, the causes and consequences of MMEs in Atlantic salmon aquaculture are not well understood. In this study, we developed a structural network of causal risk factors for MMEs for aquaculture and the communities that depend on Atlantic salmon aquaculture. Using the Interpretive Structural Modeling (ISM) technique, we analysed the causes of Atlantic salmon mass mortalities due to environmental (abiotic), biological (biotic) and nutritional risk factors. The consequences of MMEs were also assessed for the occupational health and safety of aquaculture workers and their implications for the livelihoods of local communities. This structural network deepens our understanding of MMEs and points to management actions and interventions that can help mitigate mass mortalities. MMEs are typically not the result of a single risk factor but are caused by the systematic interaction of risk factors related to the environment, fish diseases, feeding/nutrition and cage‐site management. Results also indicate that considerations of health and safety risk, through pre‐ and post‐event risk assessments, may help to minimize workplace injuries and eliminate potential risks of human fatalities. Company and government‐assisted socio‐economic measures could help mitigate post‐mass mortality impacts. Appropriate and timely management actions may help reduce MMEs at Atlantic salmon cage sites and minimize the physical and social vulnerabilities of workers and local communities.

Not that many leech species after all: Myzobdella lugubris and Myzobdella patzcuarensis (Annelida: Hirudinida) are the same species

The genus Myzobdella groups five species of leeches parasites of fishes mainly of freshwater but with tolerance to brackish waters. Native distribution of these species includes the New World from North to South America. Myzobdella lugubris Leidy, 1851, the type species of the genus, was briefly described based on specimens from the USA, but subsequently their morphology, known distribution and host range were expanded; however, less is known about the other four species of the genus. As part of a survey focusing on characterizing the diversity of leeches from Mexico, specimens of Myzobdella patzcuarensis (Caballero, 1940), from the type locality of the species were included for the first time in a phylogenetic study. In addition, specimens assigned to Myzobdella from the southeast of Mexico as well as from Nicaragua, were also included. In the resulting phylogenetic tree, our newly generated sequences were found nested in the same clade that M. lugubris; with unresolved relationships and relatively low genetic divergence, suggesting conspecificity. In addition, the internal morphology of the specimens of Myzobdella from Mexico is consistent with the description of M. lugubris. Our morphological examination reveals high degrees of variability in the external pigmentation of the specimens. Based on our results we formally synonymize M. patzcuarensis under M. lugubris.

Acute Cholecystitis Due to Lactococcus lactis and Single-Center Experience with Infections Due to Lactococcus spp.

Background: Lactococcus species are used to ferment milk to yogurt, cheese, and other products. The gram-positive coccus causes diseases in amphibia and fish and is a rare human pathogen. Patients and Methods: A 51-year-old male underwent laparoscopic cholecystectomy for acute and chronic calculous cholecystitis. Lactococcus lactis was isolated from pus from his gallbladder empyema. Results: Our institutional database was searched for other cases of Lactococcus spp. infections and four patients (2 males, 2 females; aged 51, 64, 78, and 80 years) were identified during a four-year period. The three other patients had positive blood cultures associated with pneumonia, toxic megacolon, and severe gastroenteritis. All isolates were monocultures with Lactococcus lactis (2), Lactococcus garvieae (1) and Lactococcus raffinolactis (1). Two patients died related to their sepsis. We report the second case of cholecystitis involving Lactococcus. Conclusions: Lactococcus is a very rare pathogen mainly causing blood stream infections but needs to be considered to cause serious surgical infections in humans.

Recent advances of Terminalia catappa and its application in fish culture: A review

AbstractHigh‐intensity aquaculture may cause the aquatic animals to experience elevated stress levels, which in turn will increase their susceptibility to illness and result in substantial losses. Farmers frequently use chemical and antibiotic treatments for fish diseases, which have led to drug‐resistant and hazardous residues in farmed fish and the environment. Consequently, finding substitutes for chemicals and antibiotics is crucial for disease management in aquaculture. Terminalia catappa L. or commonly called Indian almond is well known for its medicinal properties and widely distributed in tropical and subtropical regions. T. catappa contains chemical compounds such as tannin and flavonoid that play an important role in antibacterial, anti‐allergy, anti‐inflammation, and anti‐cancer. Numerous studies have been conducted on leaves, bark, fruits, and seed of T. catappa for their applications, including medicinal, bioremediation (dye absorption), and aquaculture use. Much research can be found on the utilization of T. catappa leaves to improve fish well‐being, mostly in the ornamental fish industry. Extract of T. catappa has been found to improve fish survival, growth rate, inhibit bacterial infection, improve water quality, enhance fish colouration, and boost the immune response. Although T. catappa leaves have undergone substantial research, it has not been systematically described in connection to fish species used in aquaculture. This review will systematically discuss the biotoxicity of T. catappa evaluation of growth‐promoting properties, eggs and larviculture performance, and enhancement of fish resistance to various bacteria, fungi, and parasites. In addition, the article also highlights the future perspectives of using T. catappa to improve fish culture.

Exploring the Underlying Mechanisms of Enteritis Impact on Golden Pompano (Trachinotus ovatus) through Multi-Omics Analysis

Enteritis posed a significant health challenge to golden pompano (Trachinotus ovatus) populations. In this research, a comprehensive multi-omics strategy was implemented to elucidate the pathogenesis of enteritis by comparing both healthy and affected golden pompano. Histologically, enteritis was characterized by villi adhesion and increased clustering after inflammation. Analysis of the intestinal microbiota revealed a significant increase (P<0.05) in the abundance of specific bacterial strains, including Photobacterium and Salinivibrio, in diseased fish compared to the healthy group. Metabolomic analysis identified 5479 altered metabolites, with significant impacts on terpenoid and polyketide metabolism, as well as lipid metabolism (P<0.05). Additionally, the concentrations of several compounds such as calcitetrol, vitamin D2, arachidonic acid, and linoleic acid were significantly reduced in the intestines of diseased fish post-enteritis (P<0.05), with the detection of harmful substances such as Efonidipine. In transcriptomic profiling, enteritis induced 68 upregulated and 73 downregulated genes, predominantly affecting steroid hormone receptor activity (P<0.05). KEGG pathway enrichment analysis highlighted upregulation of SQLE and CYP51 in steroidogenesis, while the HSV-1 associated MHC1 gene exhibited significant downregulation. Integration of multi-omics results suggested a potential pathogenic mechanism: enteritis may have resulted from concurrent infection of harmful bacteria, specifically Photobacterium and Salinivibrio, along with HSV-1. Efonidipine production within the intestinal tract may have blocked certain calcium ion channels, leading to downregulation of MHC1 gene expression and reduced extracellular immune recognition. Upregulation of SQLE and CYP51 genes stimulated steroid hormone synthesis within cells, which, upon binding to G protein-coupled receptors, influenced calcium ion transport, inhibited immune activation reactions, and further reduced intracellular synthesis of anti-inflammatory substances like arachidonic acid. Ultimately, this cascade led to inflammation progression, weakened intestinal peristalsis, and villi adhesion. This study utilized multi-level omics detection to investigate the pathological symptoms of enteritis and proposed a plausible pathogenic mechanism, providing innovative insights into enteritis verification and treatment in offshore cage culture of golden pompano.

Pathogen identification and epidemic factor analysis of yellow catfish, Pelteobagrus fulvidraco, red lower jaw disease

Since 2020, another type of epidemic disease, ‘red lower jaw disease’ (RLJD), has broken out in yellow catfish Pelteobagrus fulvidraco every spring in China, causing large-scale deaths and significant economic losses. This new disease has the characteristics of strong infectivity, high mortality and a single host. To prevent and control RLJD, epidemiological investigation, transmission electron microscopy (TEM), virome sequencing, Koch's rule verification and epidemic factor investigation were studied in this article. The clinical symptoms of diseased yellow catfish were pale gill filaments, hyperaemia and swelling of the spleen and kidney. TEM results revealed that a large number of 35–40 nm spherical virus particles without envelope structure were found in the cytoplasm of spleen cells. The liver, spleen and kidney of the diseased fish had serious lesions. After virome sequencing, the calicivirus reads in the unique virus reads accounted for 99.5% of the unique virus reads in the diseased fish, which provided a relevant reference value for identifying the pathogen of RLJD. The full-length sequence of yellow catfish calicivirus (YCCV) obtained at 7405 bp, including the RNA-helicase domain, RdRp-1 domain and d1iqqa domain. At the same time, both PCR and TaqMan fluorescence quantitative PCR detection method of YCCV were established. Through the artificial infection test, YCCV was verified as the pathogen for RLJD. It was also found that YCCV mainly harmed the fish within 1 year, whereas the fish above 2 years had good resistance. The water temperature of the RLJD outbreak was mainly concentrated at 18 °C–24 °C. In the current study, after YCCV was verified as the pathogen of RLJD, epidemic factors including fish age and water temperature were studied, to the best of our knowledge, for the first time to provide a relevant theoretical basis for the pathogenic mechanism and prevention and control measures of yellow catfish RLJD.

Blunt snout bream (Megalobrama amblycephala) circARHGEF15 enhances antibacterial immunity against Aeromonas hydrophila infection via ceRNA regulatory axis

Circular RNAs (circRNAs) can be used as therapeutic targets for various human diseases through competitive endogenous RNA (ceRNA). Earlier research in our laboratory has revealed that circRNAs could serve as ceRNA to sponge microRNAs (miRNAs) and regulate the innate immune response of blunt snout bream (Megalobrama amblycephala) after Aeromonas hydrophila infection, but the specific regulation is still uncertain. In this research, by means of overexpression/RNAi, qPCR, and luciferase assay etc., we discovered a circRNA termed circARHGEF15, which was upregulated following A. hydrophila challenge and positively regulated antibacterial immunity in the host. Moreover, we observed that miR-214 can restore the promotion of inflammatory factors due to circARHGEF15 overexpression. Further, our data indicated that circARHGEF15 may function as a ceRNA of miR-214 in the immune reaction generated by A. hydrophila, reduce the inhibition of miR-214 on hepcidin, and promote the expression of downstream proinflammatory factors such as il-1β, il-6, il-8, and tnf-α. In summary, the results of this study suggest that M. amblycephala circARHGEF15 acts a significant function in the modulation of antibacterial response to A. hydrophila infection, and lays the foundation for rapid diagnosis, effective control, and treatment of fish diseases from the perspective of circRNAs in the future.

Determination and Characterization of Novel Papillomavirus and Parvovirus Associated with Mass Mortality of Chinese Tongue Sole (Cynoglossus semilaevis) in China

A massive mortality event concerning farmed Chinese tongue soles occurred in Tianjin, China, and the causative agent remains unknown. Here, a novel Cynoglossus semilaevis papillomavirus (CsPaV) and parvovirus (CsPV) were simultaneously isolated and identified from diseased fish via electron microscopy, virus isolation, genome sequencing, experimental challenges, and fluorescence in situ hybridization (FISH). Electron microscopy showed large numbers of virus particles present in the tissues of diseased fish. Viruses that were isolated and propagated in flounder gill cells (FG) induced typical cytopathic effects (CPE). The cumulative mortality of fish given intraperitoneal injections reached 100% at 7 dpi. The complete genomes of CsPaV and CsPV comprised 5939 bp and 3663 bp, respectively, and the genomes shared no nucleotide sequence similarities with other viruses. Phylogenetic analysis based on the L1 and NS1 protein sequences revealed that CsPaV and CsPV were novel members of the Papillomaviridae and Parvoviridae families. The FISH results showed positive signals in the spleen tissues of infected fish, and both viruses could co-infect single cells. This study represents the first report where novel papillomavirus and parvovirus are identified in farmed marine cultured fish, and it provides a basis for further studies on the prevention and treatment of emerging viral diseases.

Aspect-based sentiment analysis for fish diseases using a feature interaction model based on adversarial strategy

Aspect-based sentiment analysis for fish diseases using a feature interaction model based on adversarial strategy

Induction of trained immunity using β-glucan and its protective responses in Nile tilapia, Oreochromis niloticus

Emerging and re-emerging diseases in fish cause drastic economic losses in the aquaculture sector. To combat the impact of disease outbreaks and prevent the emergence of infections in culture systems, understanding the advanced strategies for protecting fish against infections is inevitable in fish health research. Therefore, the present study aimed to evaluate the induction of trained immunity and its protective efficacy against Streptococcus agalactiae in tilapia. For this, Nile tilapia and the Tilapia head kidney macrophage primary culture were primed using β-glucan @200 μg/10 g body weight and 10 μg/mL respectively. Expression profiles of the markers of trained immunity and production of metabolites were monitored at different time points, post-priming and training, which depicted enhanced responsiveness. Higher lactate and lactate dehydrogenase (LDH) production in vitro suggests heightened glycolysis induced by priming of the cells using β-glucan. A survival rate of 60% was observed in β-glucan trained fish post challenge with virulent S. agalactiae at an LD50 of 2.6 × 107 cfu/ml, providing valuable insights into promising strategies of trained immunity for combating infections in fish.

Identification and florfenicol-treatment of pseudomonas putida infection in gilthead seabream (Sparus aurata) fed on tilapia-trash-feed

The present study aimed to determine the major cause of the high mortality affecting farmed gilthead seabream (Sparus aurata) and controlling this disease condition. Fifteen diseased S. aurata were sampled from a private fish farm located at Eldeba Triangle, Damietta, fish showed external skin hemorrhages, and ulceration. Bacterial isolates retrieved from the diseased fish were identified biochemically as Pseudomonas putida and then confirmed by phylogenetic analysis of the 16 S rRNA gene sequence. P. putida was also isolated from three batches of tilapia-trash feed given to S. aurata. Biofilm and hemolytic assay indicated that all P. putida isolates produced biofilm, but 61.11% can haemolyse red blood cells. Based on the antibiotic susceptibility test results, P. putida was sensitive to florfenicol with minimum inhibitory concentrations ranging between 0.25 and 1.0 µg mL− 1, but all isolates were resistant to ampicillin and sulfamethoxazole-trimethoprim. Pathogenicity test revealed that P. putida isolate (recovered from the tilapia-trash feed) was virulent for S. aurata with LD50 equal to 4.67 × 107 colony forming unit (CFU) fish− 1. After intraperitoneal (IP) challenge, fish treated with 10 mg kg− 1 of florfenicol showed 16.7% mortality, while no mortality was recorded for the fish group that received 20 mg kg− 1. The non-treated fish group showed 46.7% mortality after bacterial challenge. HPLC analysis of serum florfenicol levels reached 1.07 and 2.52 µg mL− 1 at the 5th -day post-drug administration in the fish groups received 10 and 20 mg kg− 1, respectively. In conclusion, P. putida was responsible for the high mortality affecting cultured S. aurata, in-feed administration of florfenicol (20 mg kg− 1) effectively protected the challenged fish.

Hematological and Histological Analysis of Tilapia (Oreochromis Niloticus) Cultured in Floating Net Cages After Disease Outbreak

Recently, Tilapia fish cultivated in floating net cages in Karang Intan District experienced a sudden death from June 4 to June 5. At some point, mortality reached 50% of the population in floating net cages. The purpose of this study was to analyze the hemtology and histology of tilapia (Oreochromis niloticus) after exposure to disease outbreaks that were cultivated in floating net cages. The research location was carried out at the Laboratory of Fish Pests and Diseases, Faculty of Fisheries and Maritime Affairs, University of Lambung Mangkurat. The animal samples used were tilapia showing clinical symptoms of sick fish obtained from floating net cages in Mali-Mali Village, Karang Intan District, which experienced quite high fish mortality cases and 3 fish were taken. Based on the results of hemtological analysis of tilapia (Oreochromis niloticus) after being exposed to disease outbreaks which were cultivated in floating net cages, the hemoglobin levels of tilapia obtained in this study ranged from 6.9-7.8 g/dl, the average hematocrit of tilapia was obtained in this study has a range between 37.2 - 58.9%, the average tilapia leukocrit obtained in this study has a range between 2.89 - 6.61% and blood plasma is a liquid component of blood consisting of 99% water and 8-9% protein.

Antibacterial activity of the black soldier fly (Hermetia illucens) larva protein hydrolysates against some pathogenic bacterial strains on freshwater fish

The study was carried out to determine the antibacterial activity of protein hydrolysates from black soldier fly (Hermetia illucens) larva (PHBSF) on some pathogenic bacteria including E. ictaluri, A. hydrophila, A. verroni, and S. agalactiae on freshwater fish. The results showed that the tested bacteria were highly sensitive with significant difference (P &lt; 0.05) in diameter clear zone compared to the negative control at the tested concentrations of 20, 35, and 70 mg/100 µL. Particularlly, E. ictaluri was sensitive at all three test concentrations with the diameter of clear zones following 14.0 ± 1.0, 18.7 ± 0.7, and 20.7 ± 0.7 mm, respectively. A. veronii and S. agalactiae were sensitive at concentrations of 35 and 70 mg/100 µL, and A. hydrophila with a clear zone diameter of 14.3 ± 0.3 mm at the concentration of 70 mg/100 µL. The PHBSF was able to kill A. veronii and S. agalactiae with MIC (minimum inhibitory concentration) = MBC (minimum bactericidal concentration) = 44 mg/mL, while E. ictaluri and A. hydrophila were inhibited at MIC 44 mg/mL, and MBC was 88 mg/mL. These results indicated that PHBSF could be potentially used to prevent fish diseases caused by E. ictaluri, A. hydrophila, A. verroni, and S. agalactiae.

Risk assessment of wild fish as environmental sources of red sea bream iridovirus (RSIV) outbreaks in aquaculture.

Red sea bream iridovirus (RSIV) causes substantial economic damage to aquaculture. In the present study, RSIV in wild fish near aquaculture installations was surveyed to evaluate the risk of wild fish being an infection source for RSIV outbreaks in cultured fish. In total, 1102 wild fish, consisting of 44 species, were captured from 2 aquaculture areas in western Japan using fishing, gill nets, and fishing baskets between 2019 and 2022. Eleven fish from 7 species were confirmed to harbor the RSIV genome using a probe-based real-time PCR assay. The mean viral load of the RSIV-positive wild fish was 101.1 ± 0.4 copies mg-1 DNA, which was significantly lower than that of seemingly healthy red sea bream Pagrus major in a net pen during an RSIV outbreak (103.3 ± 1.5 copies mg-1 DNA) that occurred in 2021. Sequencing analysis of a partial region of the major capsid protein gene demonstrated that the RSIV genome detected in the wild fish was identical to that of the diseased fish in a fish farm located in the same area in which the wild fish were captured. Based on the diagnostic records of RSIV in the sampled area, the RSIV-infected wild fish appeared during or after the RSIV outbreak in cultured fish, suggesting that RSIV detected in wild fish was derived from the RSIV outbreak in cultured fish. Therefore, wild fish populations near aquaculture installations may not be a significant risk factor for RSIV outbreaks in cultured fish.

Two new dactylogyrid species (Dactylogyroidea: Dactylogyridae), gill parasites of freshwater fishes from the Peruvian Amazon, including the proposal of Peruanella n. gen.

A new genus of dactylogyrid, Peruanella n. gen., is proposed to accommodate Peruanella madredediosensis n. sp. from Brachyplatystoma tigrinum (Britski) (Siluriformes: Pimelodidae) from the Madre de Dios River, in Puerto Maldonado City, Madre de Dios region, Peru. The new genus differs from Neotropical dactylogyrids by possessing a combination of the following features: (1) tandem gonads, (2) a tubular J-shaped MCO, (3) an accessory piece connected to the base of the MCO via a filament, (4) a midventral vaginal aperture, (5) anchors similar in shape, each with short roots, (6) straight and robust bars, and (7) equal hook, each with undilated shanks and a depressed thumb. A previously described species, Demidospermus aureagarciae Morey, Rojas, Dávila, Chu &amp; De Pina, 2023 exhibits characteristics that are compatible with the diagnosis of the new genus; therefore, this species is transferred to the Peruanella n. gen. In addition, Jainus peruensis n. sp. is described from Brycon amazonicus (Spix &amp; Agassiz) (Characiformes: Bryconidae). This new species, which is the first species of the genus described in Peru and the third species infecting a bryconid host, can be differentiated from all congeneric species due to: (1) a slender MCO forming a counterclockwise loop at the proximal end, (2) an unarticulated accessory piece with a scythe-shaped distal end, (3) a rod-shaped ventral bar with a medial projection, and (4) a V-shaped and grooved dorsal bar.

Effect of dietary Moldavian balm (Dracocephalum moldavica L.) on growth performance, antioxidant status, immune response, and gene expression of common carp (Cyprinus carpio)

Abstract Chemical compounds used to prevent and control fish disease often cause environmental hazards; thus, alternative approaches as new and effective strategies are needed. The current investigation was performed with the aim of exploring the effects of dietary Moldavian balm (MB, Dracocephalum moldavica L.) on the growth, immune parameters, and antioxidant status of common carp (Cyprinus carpio). Fish (n=300, w= 3.80±0.02 g) in four groups in triplicates were supplemented with 0%, 0.5%, 1%, and 2% MB. After 42 days, it was found that feed supplements increased final weight (FW), weight gain (WG), and specific growth rate (SGR) and decreased the food conversion ratio (FCR) (P &lt; 0.05). In addition, fish supplemented with 2% MB significantly showed higher serum total protein (TP), alternative complement pathway (ACH50), and glutathione peroxidase (GPx) (P &lt; 0.05). The 0.5% MB-supplemented fish represented higher levels of LYZ, alkaline phosphatase (ALP), total Ig, and ACH50 in their skin mucus in comparison with the unsupplemented fish (P &lt; 0.05). The results also indicated that 2% MB resulted in a significantly higher expression level of intestinal tumor necrosis factor (TNF- α) (P &lt; 0.05); however, the level of LYZ, interleukin-1β (IL-1β), and TLRs decreased in supplemented fish. CAT and SOD expressions were increased in 0.5% MB supplement. In conclusion, MB could be recommended as an efficient feed additive to boost common carp’s growth, immunity, and health status.