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Parasitism is increasingly seen as an ecological factor contributing to behavioural variation among individuals. Yet, the causal direction of the relationship between animal personality and parasites remains unclear. We measured behavioural traits (i.e. exploration, activity, boldness) in pumpkinseed sunfish, Lepomis gibbosus , before and after an experimental infection using cages in a lake where sunfish were naturally exposed to trematode and cestode infection for 1 month. Despite our initial assumptions (i.e. that all individuals would have the same risk of infection within a cage), we found that initial behavioural traits strongly influenced infection susceptibility: initially bolder and less active fish acquired a higher density of trematode and cestode parasites during the infection period. Following infection, fish body condition decreased with increasing cestode density, suggesting that infection is costly to hosts. Body condition was positively correlated with distance moved, a measure of activity, regardless of individual infection status. The repeatability of exploration and activity behaviour and the strength of the activity–exploration correlation (i.e. behavioural syndrome) were reduced following parasite exposure. Distance moved and trematode density were negatively correlated, suggesting that this infection decreases host activity levels. Since trematodes have a complex life cycle with piscivorous birds as a final host, a decrease in activity following infection may make infected fish more susceptible to bird predation, benefiting the parasite. Our results highlight the close links between behaviour and parasitism. We propose that two mechanisms may simultaneously operate: initial host behaviour influences their risk of infection, and infection introduces variation in the behavioural traits of infected hosts. • We infected pumpkinseed sunfish using cages in a lake with high parasite prevalence. • We measured exploration, activity and boldness before and after parasite exposure. • Less active and bolder fish were more susceptible to infection within cages. • Fish body condition decreased with high density of a parasite causing liver damage. • Fish activity was reduced with trematode infection causing black spot disease. [ABSTRACT FROM AUTHOR]

The recent discovery of disease caused by Nucleospora braziliensis in Nile tilapia (Oreochromis niloticus) is important as it has highlighted the high prevalence of infection and associated mortality in cultured fish. Thus, this study conducted an experimental infection of this microsporidium to evaluate pathological alterations and conduct proteomic analysis. For pathological observation, samples of brain, eyes, gall bladder, gut, heart, kidney, liver, muscle, skin, spleen, and stomach tissue, were collected, and liquid chromatography–mass spectrometry (LC-MS/MS) was performed for proteomic analysis. The most prevalent lesions were brownish color of the liver, gill filament fusion, gut ischemia, hemorrhage of the lips and fins, hepatomegaly, spleen atrophy, splenomegaly, and stomach congestion. The most common microscopic lesions were degeneration, hemorrhage, and inflammation in the brain, gills, gut, kidney, liver, muscle, spleen, and stomach. The digested peptides were identified by LC-MS/MS and the intersection of each group showed that in the spleen there were 121 exclusive proteins in the infected sample and 252 in the control, while in the kidney, 129 proteins were identified in the infected specimen compared to 83 in the control. In conclusion, this study demonstrates the proteome profile of O. niloticus kidney and spleen tissue in response to infection with N. braziliensis. [ABSTRACT FROM AUTHOR]

AbstractSex plays a crucial role in shaping the immune response of vertebrates, leading to differing susceptibilities to diseases between females and males. This review explores the observed sexually dimorphic patterns in different pathogenic infections, immune responses, and molecular events. First, a compilation of historical guidelines for incorporating gender/sex as a variable in research studies to enhance scientific rigor, improve research outcomes, and promote better health for both sexes has been carried out. Following this, the study focuses on examining sex-based differences in immune responses across different taxa, with an in-depth review of available studies on fish, particularly regarding the prevalence of sex-related differences in parasites, viruses, and bacteria. Furthermore, the benefits of considering sexual dimorphism when evaluating the prevalence of diseases in fish management in aquaculture and ecological contexts have been discussed. Integrating sex in understanding immune responses will positively influence fish welfare, economic impacts, and policymaking, leading to more tailored and effective treatments. [ABSTRACT FROM AUTHOR]

Lactococcosis is a common bacterial fish disease caused by Lactococcus garvieae, L. petauri and L. formosensis. Although there are different PCR‐based techniques to identify the etiological agent, none of these can differentiate these two bacteria without sequencing PCR‐amplified fragments. In the present study, we developed a multiplex PCR assay for simultaneous detection and differentiation of L. garvieae and L. petauri. The specificity of the primers was validated against the bacterial DNA of the targeted and non‐targeted bacteria. The sizes of the PCR amplicons were obtained as 204 bp for the DUF1430 domain‐containing protein gene of L. garvieae, 465 bp for the Lichenan permease IIC component gene of L. petauri, and 302 bp for the teichoic acid biosynthesis protein F gene of both L. garvieae and L. petauri. The PCR amplicons were clearly separated by agarose gel electrophoresis. The multiplex PCR assay did not produce any amplification products with the DNA of the non‐targeted bacteria. The multiplex PCR detection limits for L. garvieae and L. petauri were 5 and 4 CFU in pure culture and 50 and 40 CFU/g in spiked tissue samples, respectively. It takes less than 2 h from plate‐cultured bacteria and 3 h from tissue samples to get results. In conclusion, the developed multiplex PCR assay is a rapid, specific, accurate, and cost‐effective method for the detection and differentiation of L. garvieae and L. petauri and is suitable to be used for routine laboratory diagnosis of L. garvieae and L. petauri. [ABSTRACT FROM AUTHOR]

In response to the challenges of accurately identifying event triggers and elements in long texts related to aquaculture, existing models struggle to differentiate between elements and triggers, as well as effectively recognize complete entity texts. To tackle this issue, this study proposes an algorithm for extracting fish disease events based on pseudo triggers and augmented event element data. The method starts by constructing pseudo samples using the original dataset. Two types of noise datasets are then generated: a trigger noise dataset constructed based on fish disease triggers and an entity noise dataset with varying levels of entity noise constructed based on fish disease entities. Next, three parallel neural networks are deployed to extract sample features from these datasets. The fish disease event extraction for the source dataset employs multi-label classification. For the trigger noise dataset, the sample features are activated using the sigmoid function, and the MRSE loss is utilized for optimization of this branch. For the entity noise dataset, the sample features are activated using the Relu function, and the XOR loss is used for optimization. Finally, the losses from the three branches are combined with weighted summation to obtain the fusion loss. The experimental results on the fish disease dataset used in this paper show that the proposed algorithm achieves an average accuracy of 78.71%, 78.95%, and 79.43% on F1, recall, and precision, respectively, which is a maximum improvement of 11.201%, 11.849%, and 12.421% in accuracy with respect to the baseline model on F1, recall, and precision, respectively. [ABSTRACT FROM AUTHOR]

Antibiotics are crucial in the control of bacterial infections on fish farms. However, the influence of licensed antibiotics on DNA damage, histological changes, and protein differentiation in some farmed fish species is unidentified. The current study aimed to investigate the effect of therapeutic (80 mg/kg body weight/day) and high doses (160 mg/kg body weight/day) of oxytetracycline (OTC) on some biological indices, protein differentiation, histological changes, and DNA damage in Oreochromis niloticus (n = 360; 40 ± 3.5 g) and the potential positive effects of dietary ascorbic acid (AA) and whether it is capable of reducing the deleterious impacts of OTC and working synergistically to increase fish disease resistance and decrease morbidity and mortality rates. In the current study, fish were fed diets with or without OTC (80 or 160 mg/kg body weight/day) and AA (100 mg/kg diet/day) for 28 days, followed by a bacterial stress test with two different virulent strains for 14 days. Treatments include CTR (control; without additives), AA, OTC80, OTC160, OTC80 + AA, and OTC160 + AA. The results revealed that the AA group had the best antioxidative (significant increase in SOD, CAT, and GPx) and immunomodulatory effects (an increase in IgM, nitroblue tetrazolium, and total leucocytic count). Furthermore, the hematological parameters, immune indices (NBT), and antioxidant enzymes were significantly reduced by OTC160 (p ≤ 0.05). The results also showed that OTC160 notably augmented the activity of liver (ALT, AST, and LDH) and kidney (creatinine and urea) damage markers (p ≤ 0.05). OTC160 revealed considerable hepatic and renal tissue damage and significantly higher hepatocyte DNA damage. Pathological changes and DNA damage were directly correlated to the dosage of OTC exposure, where they were more severe in OTC160. OTC80 showed insignificant changes in most parameters. Compared to CTR, the inclusion of AA in the O. niloticus diet significantly restored the biological indices, histological changes, and DNA damage in OTC-treated groups. The morbidity and mortality percentages after bacterial challenge were significantly lower in the OTC80 + AA group, followed by the OTC160 + AA group than in the CTR. These results corroborate the use of AA as a potent antioxidant and immune stimulant and a potential co-adjuvant to OTC in the diet of O. niloticus to reach optimal resistance to disease. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, environmental DNA technology, 16S rRNA gene sequencing, and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were employed to investigate the relationships between Tetrahymena pyriformis, bacteria, and guppies under varying temperature and pH conditions. The abundance of T. pyriformis in water, the relative abundance of bacterial species, and histopathological observations were studied. Results of this study showed that several bacteria were related to T. pyriformis, and environmental factors affected the interaction between bacteria and T. pyriformis. In the aquaculture system of ornamental fish, the interaction between bacterial microbiota and ciliate protozoa can prevent or promote disease outbreaks, and different physicochemical conditions will affect the relationships between them. We investigated the interaction between bacterial microbiota and the parasite Tetrahymena pyriformis when infecting Poecilia reticulata (guppy) under different physicochemical conditions. The abundance of T. pyriformis in water, the relative abundance of bacterial species, and histopathological observation were studied or monitored using environmental DNA (eDNA) extraction technology, the qPCR method, and 16s rRNA sequencing, respectively. The morphological identification and phylogenetic analysis of T. pyriformis were carried out. The infected guppy tissue was also stained by the hematoxylin and eosin methods. The results showed: (1) the bacterial communities of water samples were mainly composed of species assigned to Proteobacteria and Bacteroidetes, and Tabrizicola and Puniceicoccaceae were positively correlated with fish mortality, T. pyriformis abundance, and temperature. (2) Arcicella and Methyloversatilis universalis with different correlations between ciliates appeared in different treatment groups, the result of which proved that environmental factors affected the interaction between bacteria and T. pyriformis. (3) Lower temperatures and a higher pH were more beneficial for preventing disease outbreaks. [ABSTRACT FROM AUTHOR]

EU Member States should ensure that they implement adequate health surveillance schemes in all aquaculture farming areas, as appropriate for the type of production. This study presents the results of applying the FAO's Surveillance Evaluation Tool (SET) to assess the Spanish disease surveillance system for farmed fish species, which although applied previously in livestock production, is applied here to aquaculture for the first time. Overall, there were important score differences between trout and marine fish (seabass and seabream) surveillance, which were higher for trout in the following areas: Institutional (70.8% versus 50.0%), Laboratory (91.7% versus 47.2%), and Surveillance activities (75.3% versus 61.3%). For other categories, the values were lower and no significant differences were found. However, most surveillance efforts focused only on trout, for which there are EU and WOAH listed (notifiable) diseases. In contrast, for seabream and seabass, for which there are no listed diseases, it was considered that surveillance efforts should, nevertheless, be in place and should focus on the identification of abnormal mortalities and emerging diseases, for which there are as yet no standardized harmonised methodologies. [ABSTRACT FROM AUTHOR]

Lactococcus garvieae has recently been identified and listed as one of the causative agents of hyperacute hemorrhagic sepsis in fish. In intensive recirculating aquaculture systems where there are high fish densities and minimal water changes, not only will it be conducive to the growth of bacteria, but Cryptocaryon irritans as a marine protozoan fish parasite is also prone to appear. This study reports the disease status of Trachinotus ovatus in an aquaculture area in Yangjiang City, Guangdong Province. Through the diagnosis of clinical symptoms of the diseased fish, identification of specific primers, 16s rRNA sequences phylogenetic tree analysis, physiological and biochemical identification, and observation of histopathological sections, the result of the experiment is that the mass death of T. ovatus is caused by a mixture of L. garvieae and C. irritants infections. Subsequently, regression infection experiments were performed to verify Koch's law. It was confirmed that the pathogen had strong virulence to T. ovatus. This is the first time that the co-infection of L. garvieae and C. irritans to T. ovatus was found in South China. The research results of this experiment have certain enlightenment significance for the epidemic trend of fish diseases in relevant sea areas. [ABSTRACT FROM AUTHOR]

Aporosa cardiosperma is a plant species majorly found in the Indian Western Ghats that belongs to the phyllanthaceae family with ethnobotanical importance. Using a Fourier Transform-Infrared Spectrometer (FT-IR) and Gas Chromatography-Mass Spectrometry (GC–MS) for evaluating leaf extracts of A. cardiosperma, significant functional groups and metabolite constituents were determined, and its total flavonoid, phenol, and tannin content were quantified. Further, its antibacterial efficacy was investigated against microorganisms that cause fish and human disease and are resistant to common antibiotics, including Staphylococcus aureus, Bacillus subtilis, Mycobacterium tuberculosis, Klebsiella pneumoniae, Aeromonas hydrophila, and Pseudomonas aeruginosa. Regarding the outcomes of GC–MS analysis, the primary metabolites in the A. cardiosperma leaf extracts were heneicosane (57.06%), silane (13.60%), 1-heptadecene (10.09%), 3-hexadecene (9.99%), and pentadecane (9.54%). In comparison to other solvents, methanolic extract of A. cardiosperma leaves had increased phenolic, flavonoid, and tannin content; these findings are consistent with in vitro antioxidant potential and obtained that the methanolic extract (100 µg/mL) exhibited the higher percentage of inhibition in DPPH (82.35%), FRAP (86.20%), metal chelating (72.32%), and ABTS (86.06%) antioxidant assays respectively. Similar findings were found regarding the antibacterial efficacy against pathogenic bacteria. Comparatively, to other extracts, methanolic extracts showed more significant antibacterial activity at a lower minimum inhibitory concentration (MIC) value (250 µg/mL), whilst ethyl acetate and hexane solvent extracts of A. cardiosperma leaves had higher MIC values 500 µg/mL and 1000 µg/mL respectively. The antimicrobial potential was validated by investigating bacterial growth through the extracts acquired MICs and sub-MICs range. Bacterial growth was completely inhibited at the determined MIC range. In conclusion, A. cardiosperma leaf extract's phytochemical fingerprint has been determined, and its potent antibacterial and antioxidant activities were discovered. These findings of the current study will pave the way for developing herbal treatments from A. cardiosperma for various fish and human diseases. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to explore the potential of Murraya koenigii as a natural alternative to synthetic antimicrobial agents for the treatment of edwardsiellosis in gourami fish (Osphronemus goramy). This research employed a combination of both experimental and descriptive methods. The research followed a two-stage approach. In the first stage, antibacterial compounds were extracted and characterized from M. koenigii leaves, followed by an assessment of their antibacterial activity against Edwardsiella tarda. The second stage involved applying the crude extract of M. koenigii, known for its antibacterial properties, to gourami fish infected with E. tarda. The findings revealed that M. koenigii predominantly contains alkaloids, terpenoids, saponins, flavonoids, and tannins, all of which exhibit antibacterial activity. The application of the crude M. koenigii extract had a substantial impact on the hematological profile of the infected gourami fish. The most effective dose in treating Edwardsiellosis in gourami fish was found to be 600 mg/L, as it significantly improved various hematological parameters, including hematocrit, hemoglobin, erythrocyte count, leukocyte count, lymphocytes, monocytes, and neutrophils. Additionally, histopathological analysis showed improvements in tissue conditions, with lower scores for degeneration, congestion, and necrosis. Furthermore, the survival rate of gourami fish reached its highest at 83.33% when treated with the 600 mg/L dose of M. koenigii extract. These results suggest the potential of M. koenigii as an effective alternative for the treatment of Edwardsiellosis in gourami fish. However, further research is needed to assess the practical application of M. koenigii extract in gourami fish culture. [ABSTRACT FROM AUTHOR]

Aeromonas salmonicida is a common pathogen of salmonid fishes that poses a significant threat to the fresh water and marine culture industry, potentially resulting in huge economic losses. To prevent and control fish diseases caused by A. salmonicida, rapid and effective diagnostic approaches must be developed, and which are important for routine monitoring and clinical care. By combining recombinase polymerase amplification (RPA) technology with a visible lateral flow strip (RPA-LF), we have enhanced both the precision of RPA detection and the convenience of real-time monitoring. In this study, we introduce a robust method for detecting A. salmonicida using RPA-LF. This assay specifically targets the ASA_1441 gene of A. salmonicida, ensuring high specificity, without cross-reactivity with other prevalent fresh water or marine pathogens. The optimal amplification temperature of the RPA assay was 39 °C. Its sensitivity extends to as low as 100 fg of purified DNA, representing more than 1000-fold higher sensitivity than conventional PCR methods. Furthermore, to enhance the usability of the RPA-LF assay, we developed a rapid sample preparation method using cellulose dipsticks for nucleic acid extraction. This method achieves a limit of detection (LOD) as low as 1.67 CFU/µL and completes the entire process within 20 min. In conclusion, our findings present a rapid and precise tool for monitoring A. salmonicida infection in aquaculture and marine culture. This advancement offers valuable insights for effective disease prevention and control strategies. [ABSTRACT FROM AUTHOR]

Vaccination is an effective way to control many infectious diseases in fish. Israeli fish farming has successfully used two vaccines over the last 30 years and has no problem with the side effects of vaccination. However, after introducing new species, a new problem emerged: these fish, after vaccination, demonstrated peritoneal lesions such as granulomas. At the same time, the fish did not show retarded growth or suffering during the fattening period. This study was conducted to establish the connection between vaccination and the appearance of granulomas. Evidence drawn from this research work and comparing vaccinated and non-vaccinated fish confirms that intraperitoneal granulomas do not impact the growth, performance, or fish fillet quality at harvest. [ABSTRACT FROM AUTHOR]

Disease prevention and control are a crucial aspect of fishery management, as they ensure the sustainability of aquacultural systems. With a specific focus on Shandong Province, China, this study outlines the occurrence of diseases in aquatic organisms. It summarizes dynamics that drive disease prevention and control and supports technology, work mode, and emergency prevention and control. In addition, this study also delves into the role of epidemic prevention and control institutions, the upgrading of the social service of disease prevention systems, and insufficient technical support for new species and models. Overall, the findings outlined in this study are intended to achieve the following aims: enhance organizational management of disease prevention and control, standardize the implementation of social services, improve research into prevention and control technologies, and highlight the importance of information technology in disease prevention and control. Based on practical aquaculture production, our aim is to comprehensively analyze the situation of the construction of a disease prevention and control system, strengthen guidance on epidemic prevention technologies, establish a robust animal epidemic prevention system, and propose development strategies, serving as a reference for competent authorities to enhance the disease prevention and control of aquatic organisms. [ABSTRACT FROM AUTHOR]

Rapid growth of antimicrobial resistance is a major threat to human and animal health, and development of new drugs with effective microbicidal properties are in demand to the scientific communities. Cyanobacteria and medicinal plants inherit antimicrobial, antioxidant, anti-cancerous and anti-inflammatory properties. In the current research, we investigated antibacterial potential of crude ethanolic extracts from marine microalgae (Chlorella sp. and Spirulina sp.) and medicinal plants (Aloe vera and Clinacanthus nutans) against pathogenic bacteria isolated from chicken, dog, fish, and shellfish. Bacteria including Salmonella sp., Aeromonas sp. and E. coli, Vibrio sp. Streptococcus sp. and Staphylococcus sp., were isolated through colony morphology, Gram staining and VITEK-2 tests. Antibacterial activity was determined by disc diffusion assay. Spirulina sp. showed the highest inhibition zone of 19.3±0.58 mm against Vibrio sp. compared to other treatments, whereas Chlorella sp. exhibited maximum inhibition zone of 11.41±0.65 mm against Staphylococcus sp., C. nutans had antibacterial activity against Staphylococcus sp. and E. coli with the maximum zone of inhibition (14.21±1.08 and 15.10±0.21 mm), whereas Aloe vera against E. coli and Vibrio sp. with significant inhibition zone of 14.04±0.90 and 15.36±1.11mm, respectively. Minimum inhibitory concentration (MIC) of Chlorella sp. was found to be 20 mg/mL against all the test bacteria. Spirulina sp., Aloe vera, and C. nutans had MIC values ranging from 20-40 mg/mL. These findings highlight the antibacterial potential of native microalgae and medicinal plants against virulent bacteria that poses significant threats in poultry, canine and aquaculture. [ABSTRACT FROM AUTHOR]

Cyprinid herpesvirus 2 (CyHV-2), a member of the Alloherpesviridae family belonging to the genus Cyprinivirus, was initially isolated from goldfish (Carassius auratus) and has been recently emerging as a virulent pathogen for cultured prussian carp (Carassius auratus gibelio) world-wide. In this study, a novel and effective method for concentration and quantification of live CyHV-2 virions from water was successfully established through coupling the iron flocculation with real time qPCR assay. Then, the shedding intensity of CyHV-2 in fish-tank water from artificially-challenged goldfish (25 fish/20 L) was monitored continuously for 7 days on a daily basis through quantitating viral genomic copy numbers by qPCR, and the maximum shedding level was determined to be 105 copies/L. Horizontal transmission research system was established by inoculating healthy goldfish in water spiked with serial dilution of CyHV-2 virions ranging from 107 to 10³ copies/L. Our results indicated that water-borne CyHV-2 efficiently caused the infection of tested goldfish even in a concentration of 10³ copies/L, and the overall transmission efficacy was not linearly correlated with the level of input virus in the fish tank. Commercial disinfectant Composite Sodium Chlorite Powder (CSCP) has been widely applied in aquaculture to control microbial infection through direct spill in the water, and its effect in inactivating the CyHV-2 infectivity remains unknown. We further determined that the EC50 of CSCP against 3.89 TCID50/mL CyHV-2 was close to 15.625 µg/mL in vitro, and application of CSCP in a level as high as 60 µg/mL (the safety concentration of CSCP for goldfish) couldn't protect goldfish from CyHV-2 challenge through immersion. Thus, the disinfectant CSCP was regarded as none-effective for blocking CyHV-2 transmission in water during epidemic. Overall, our data provided quantitative data to demonstrate the shedding intensity of CyHV-2 in water, and CSCP was shown to be not effective in blocking water-borne horizontal transmission of CyHV-2 in goldfish. The virus-concentration protocol and virus-inhibition assay established here also paved the way for evaluating more commercial disinfectants in their effects in blocking water-borne horizontal transmission of CyHV-2. [ABSTRACT FROM AUTHOR]

Aquaculture is a critical source of seafood production, addressing the global demand for fish products. Suggesting a Deep learning-based classification technique for fishes specifically Indian Major Carp (IMC) as Mrigala, Catla and Rohu is the major objective of this paper along with detecting the disease among them. This world inside hydrosphere has their own discrete living manner. Yet they are not untouched by diseases; fishes mostly affected when young carry pathogens which cause various infections naturally or due to environmental pollutants including chemical and hazardous waste. This paper proposed the classification and prediction of diseases of fishes in aquaculture using Deep Learning based customized Convolutional Neural Network with ResNet-50 model. The proposed model performance metric compared with recent state-of-art techniques. ResNet-50 classifies accurately the IMC and type of disease the fishes are suffering from. [ABSTRACT FROM AUTHOR]

Some parasites manipulate their hosts phenotype to enhance predation rates by the next host in the parasites life cycle. Our understanding of this parasite-increased trophic transmission is often stymied by study-design challenges. A recurring difficulty has been obtaining uninfected hosts with a coevolutionary history with the parasites, and conducting experimental infections that mimic natural processes. In 1996, Lafferty and Morris provided what has become a classic example of parasite-increased trophic transmission; they reported a positive association between the intensity of a brain-infecting trematode (Euhaplorchis californiensis) in naturally infected California killifish (Fundulus parvipinnis) and the frequency of conspicuous behaviors, which was thought to explain the documented 10-30× increase in predation by the final host birds. Here, we address the primary gap in that study by using experimental infections to assess the causality of E. californiensis infection for increased conspicuous behaviors in F. parvipinnis. We hatched and reared uninfected F. parvipinnis from a population co-occurring with E. californiensis, and infected them 1-2 times/week over half their life span with E. californiensis and a small cyathocotylid trematode (SMCY) that targets the hosts muscle tissue. At 3 time points throughout the hosts lives, we quantified several conspicuous behaviors: contorting, darting, scratching, surfacing, and vertical positioning relative to the waters surface. Euhaplorchis californiensis and SMCY infection caused 1.8- and 2.5-fold overall increases in conspicuous behaviors, respectively. Each parasite was also associated with increases in specific conspicuous behaviors, particularly 1.9- and 1.4-fold more darting. These experimental findings help solidify E. californiensis-F. parvipinnis as a classic example of behavioral manipulation. Yet our findings for E. californiensis infection-induced behavioral change were less consistent and strong than those previously documented. We discuss potential explanations for this discrepancy, particularly the idea that behavioral manipulation may be most apparent when fish are actively attacked by predators. Our findings concerning the other studied trematode species, SMCY, highlight that trophically transmitted parasites infecting various host tissues are known to be associated with conspicuous behaviors, reinforcing calls for research examining how communities of trophically transmitted parasites influence host behavior.

Aquaculture in the Russian Federation is an integral part of the agricultural industry of the state economy. Countries with high rates of aquaculture growth (Norway, USA, China, Japan, Canada, etc.) and increasing efficiency of fish farming are the cradles of infectious diseases, which, in case of improper control, invade the territory of other countries and spread to new areas, bearing the risks for the domestic industry too. In recent years, infectious hematopoietic necrosis (IHN) has caused significant damage to fish farms. In 2020, Estonia suffered heavy losses; more than 65 tons of rainbow trout died and were destroyed during the IHN outbreak with a mortality rate of 71%. This was the first IHN case in this country. The aggravation of the epidemic situation at Estonian fish farms poses a threat to the northwestern regions of the Russian Federation, where aquaculture is practiced (the Leningrad Oblast and the Republic of Karelia). In 2022, IHN outbreaks were reported in France, Italy, Finland, Germany, Denmark and Macedonia. IHN-caused deaths were reported at the river trout farm in Georgia in 2023 for the first time. The domestic aquaculture depends on the import of eggs and seed material from Norway, Denmark, Finland and other countries, therefore a regular disease monitoring is urgently needed. The paper provides a brief description of the IHN causative agent, describes its epidemiology, pathogenesis, clinical signs, post-mortem lesions, diagnostic tests, infection control and prevention measures. We have reviewed 88 literature sources to summarize the information.

Abstract Regarding several infectious diseases in fish, multiple vaccinations are not favorable. The chimeric multiepitope vaccine (CMEV) harboring several antigens for multi-disease prevention would enhance vaccine efficiency in terms of multiple disease prevention. Herein, the immunogens of tilapia’s seven pathogens including E. tarda, F. columnare, F. noatunensis, S. iniae, S. agalactiae, A. hydrophila, and TiLV were used for CMEV design. After shuffling and annotating the B-cell epitopes, 5,040 CMEV primary protein structures were obtained. Secondary and tertiary protein structures were predicted by AlphaFold2 creating 25,200 CMEV. Proper amino acid alignment in the secondary structures was achieved by the Ramachandran plot. In silico determination of physiochemical and other properties including allergenicity, antigenicity, glycosylation, and conformational B-cell epitopes were determined. The selected CMEV (OSLM0467, OSLM2629, and OSLM4294) showed a predicted molecular weight (MW) of 70 kDa, with feasible sites of N- and O-glycosylation, and a number of potentially conformational B-cell epitope residues. Molecular docking, codon optimization, and in-silico cloning were tested to evaluate the possibility of protein expression. Those CMEVs will further elucidate in vitro and in vivo to evaluate the efficacy and specific immune response. This research will highlight the new era of vaccines designed based on in silico structural vaccine design.

Alternatives to conventional chemical treatments for parasitic diseases in fish are needed. Microalgal‐sourced fatty acid ethyl esters (FAEEs) have shown an antiparasitic effect against Gyrodactylus turnbulli infection in guppies. Here, we tested a range of commercial FAEEs of various carbon chain lengths and unsaturation levels against two fish parasites. Guppies and barramundi infected with G. turnbulli and Trichodina sp., respectively, were used. The most effective FAEE, after excluding those toxic to fish, was ethyl laurate (12:0). For both parasites, the LD50 was 18.75 μM within 250 min of incubation. Ethyl eicosapentaenoate (20:5n3) was the next most effective FAEE against G. turnbulli, and dihomo‐γ‐linolenic acid ethyl ester (20:3n6) and ethyl α‐linolenate (18:3n3) were the next most effective against Trichodina sp. In addition, FAEEs prepared from the microalga Phaeodactylum tricornutum residue, after fucoxanthin extraction, were examined against Trichodina sp. infection in barramundi for the first time. LD85 and LD100 was achieved at 2.5 and 5 μL mL−1 of the FAEE preparation, respectively. In vivo, immersion of infected barramundi in 1.25 μL mL−1 of this preparation for 24 h reduced infection prevalence from 100% to 53% and was non‐toxic to fish. [ABSTRACT FROM AUTHOR]

Background: Conventional munition dumped into the North Sea and the Baltic Sea close to the German coastline is corroding. A major concern is that biota, including fish, are negatively affected by toxic explosives leaking into marine environments. With the present study, we investigated fish living in close proximity to munition dumping sites for contamination and for signs of health impairments. The flat fish species common dab (Limanda limanda) was used as a model, since it lives in the vicinity of dumping sites and exhibits minor migratory activity. Since explosives are excreted via the bile, the bile fluids from dab were analysed. Further on we inspected the health status of the fish. Results: Dab caught in German coastal waters of the Baltic Sea and the North Sea were contaminated with explosives. Probably due to rapid metabolization, concentrations of the explosive 2,4,6-trinitrotoluene (TNT) were always below limit of detection, but its metabolites 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene were detected in bile fluid up to 26.36 ng/ml and 95.91 ng/ml, respectively. Only few fish from the Baltic Sea were positive for the explosive HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine with a maximum concentration of 0.89 ng/ml. Highest concentrations of TNT metabolites in bile fluid were detected in dab collected near the dumping site "Kolberger Heide" in the bay of Kiel (Baltic Sea). However, also dab from the North Sea were significantly contaminated with TNT metabolites. Conclusions: The present study showed for the first time that fish living close to near shore munition dumping sites in the North Sea are contaminated with explosives. Various health indicators (body condition factors, externally visible fish diseases, parasites or liver anomalies) showed differences in health status between fish living in the North Sea and in the Baltic Sea, respectively. However, the health status of fish caught at the most contaminated site in the Baltic Sea was not worse compared to fish living in less contaminated areas. We conclude that fish living in the vicinity of dumping sites in the North Sea and the Baltic Sea can be significantly contaminated with explosives. However, obvious health impairments of the fish were not observed. [ABSTRACT FROM AUTHOR]

Aquaculture is considered one of the fastest-growing food production sectors, which provides about 41% of the world's fish food. Different types of pathogens, including bacteria, viruses, amoebas, oomycetes, fungi, and ectoparasites, have emerged to cause serious fish diseases. Medicines such as antibiotics and chemicals as well as vaccines have been widely used to combat fish diseases. However, their undesirable use to treat fish in aquaculture develops drug resistance in the surrounding microbes, especially antibiotic resistance in fish-associated bacterial strains in the column water and sediment, is mostly the consequence of applying antibiotics in aquaculture. The rise of antibiotic resistance in aquaculture and multidrug-resistant pathogens in the food chain threatens public health, hampering infection treatment and compromising food safety. Addressing this challenge is vital to protect both public well-being and the aquaculture industry's future. Basic control measures for sustainable, disease-free aquaculture, including alteration of antibiotic resistance genes into other animal pathogens, have been driven by the potential development of antibiotics with respect to environmental impact and consumer safety. Anyhow, vaccination is an effective control measure that overcomes drug resistance conditions in aquaculture; even some therapeutic and prophylactic methods are being simultaneously applied for the treatment of fish diseases. Mostly, antibiotics and probiotics do not show strong effects after the development of new mutant strains and drug-resistant pathogens. Therefore, various types of vaccines have been developed to treat aquatic pathogens effectively by using advanced molecular techniques. Previous studies on fish vaccines have typically lacked comprehensive assessments of vaccine efficacy across varying environments and species, often focusing on single pathogens while neglecting the potential influence of pathogen interactions within complex aquatic ecosystems. This review focuses on advancements in technology and prospects of vaccines used in the aquaculture industries for reducing antibiotics usage. It also discussed the vaccination from traditional to modern new-generation ones including DNA, monovalent, and polyvalent vaccines. The objective is to provide an overview of aquaculture's major bacterial pathogens and how vaccines can substitute antibiotics to protect aquatic animals from various infectious diseases. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the effect of vitamin C supplementation on the survival rate and histopathological changes of gills and kidneys of tilapia infected by Aeromonas hydrophila. Three doses of vitamin C were tested (150; 300; and 450 mg/kg) with two control groups. Tilapia with uniform size (average weight of 14 grams) as the criteria for inclusion were randomly distributed in five ponds with 15 tilapia fish per pond. Tilapia was fed with hands until full for two weeks. Tilapia was then infected with A. hydrophila to find out the survival rate and histopathological changes of gills and kidneys at the end of the experimental period or 7 days after infection. The supplementation of 150 mg/kg vitamin C in feed increased Tilapia's survival rate (%) by 86.67% or higher than other treatment and control groups. The damage to gills in terms of lamella separation was found in all treatment groups and kidneys. The results found that the supplementation of 150 mg/kg vitamin C in feed increased survival rate but did not give effective protection on gills and kidneys. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS), which are key cellular signalling molecules, are reactive chemicals containing oxygen. Cell survival or death is a critical issue in the inflammatory response. Accumulation of ROS involves ROS generation and scavenging, which determine ROS homeostasis. Understanding the roles of ROS in modulating the inflammatory response in fish is vital for helping protect fish from the damage of water pollutants in harsh environmental conditions. ROS‐related key genes and signalling pathways are relatively conserved in fish but vary among different species. Recent frequent incidences of fish diseases have posed a considerable challenge to large‐scale aquaculture. ROS is important in stress perception, integration of diverse stress‐responsive signalling networks, and activation of animal defence mechanisms, which frequently occur during inflammation in fish. This review summarises recent studies on ROS signalling pathways during inflammation in fish. Furthermore, it examines the relationship between ROS and inflammation in fish. This review may contribute to the understanding of the underlying mechanisms by which ROS regulate inflammation in fish and provide suggestions for sustainable development in aquaculture. [ABSTRACT FROM AUTHOR]

Objective: Feed additives have attracted increased attention in aquaculture due to their ability to modulate fish gut microbiota, resulting in improved fish growth and immunity. This study assessed the effects of two synbiotics in Japanese Eel Anguilla japonica: Bacillus subtilis with mannooligosaccharides (MOS) and Enterococcus faecium with fructooligosaccharides (FOS). Methods: Six diets, including a control (CON) diet, oxytetracycline (OTC) diet, and four synbiotic diets (B. subtilis at 1 × 106 or 1 × 107 colony‐forming units [CFU]/g with MOS at 5 g/kg [BS6MO and BS7MO; collectively, BSMOS diets] and E. faecium at 1 × 106 or 1 × 107 CFU/g with FOS at 5 g/kg [EF6FO and EF7FO; collectively, EFFOS diets]), were fed to triplicate groups of 20 fish (average weight ± SD = 6.00 ± 0.07 g) for 8 weeks. Result: Fish fed the BSMOS diets showed significantly higher weight gain, specific growth rate (SGR), and feed efficiency compared to fish fed the CON and OTC diets, but the values were not significantly different from those of fish fed the EFFOS diets. Weight gain and SGR of fish that were given EFFOS diets were not significantly different from those of fish fed all other diets. Fish fed the OTC diet showed a higher mean aspartate aminotransferase level, although the difference was not statistically significant. The myeloperoxidase activity of fish fed the BS7MO diet was significantly higher than those of fish receiving all other diets, and the superoxide dismutase activity of fish fed the BS7MO diet was also significantly higher than that of fish fed the EF7FO diet. Overall, the BSMOS synbiotic diets were significantly more effective than the CON diet in enhancing fish survival against a Vibrio anguillarum challenge. Conclusion: Our findings suggest that synbiotics can be a preferable alternative to antibiotics in aquaculture. Impact statementThe Japanese Eel is an economically important fish in Korea, but its aquaculture is fraught with disease challenges and slow growth. By adding synbiotics (blends of prebiotics and probiotics) to the Japanese Eel's diet, growth and immunity were improved, suggesting a potential alternative to antibiotics. [ABSTRACT FROM AUTHOR]

Background: Exotic and ornamental fish are highly popular companion animals resulting in a significant transcontinental trade of fish, invertebrates and aquatic plants. A major issue is the diseases associated with these organisms, as they have a major impact on health of the fish in both public and private household aquaria. A secondary issue is the trade with these products, which potentially may expand the distribution area and spread a range of diseases to new habitats. Results: We here describe how Poecilia reticulata (guppy), produced in a private household aquarium, were invaded by cercariae of an exotic trematode released by imported Melanoides tuberculata snails. The fish presented with severe clinical signs (tremor, flashing, scraping of body against objects). A standard parasitological examination and morphometric identification showed scale pocket infections with a digenean trematode species within the genus Transversotrema. Molecular identification by PCR, sequencing and phylogenetic analyses of a 2646 bp sequence encoding ribosomal RNA (partial 18 S, ITS1, 5.8 S, ITS2, partial 28 S) was performed. The 1107 bp sequence of mitochondrial DNA (cox1) showed that the parasite differed from previously described Transversotrema species in M. tuberculata. Morphometrics of adult and larval specimens of this isolate also differed from previously described freshwater species within the genus. The new species was described and is named after Copenhagen, for its geographic origin. Conclusions: The genus Transversotrema comprises a range of species, adapted to a microhabitat in scalepockets of teleosts. A combination of morphological and molecular characterization techniques has been shown to provide a good differentiation between species. The fish were not purchased from a pet shop but produced in the home aquarium. This indicated that an infection pressure existed in the aquarium, where the source of infection was found to be exotic intermediate host snails M. tuberculata, which originally were imported and purchased from a pet shop. The potential spread of fish diseases associated with trade of fish and snails to new geographic regions, where climate conditions are favourable, is discussed. [ABSTRACT FROM AUTHOR]

Fish intestinal tract harbors numerous microorganisms, which exert a critical function in maintaining intestinal health and regulating nutrition metabolism. Although the most economical energy source, carbohydrates cannot be efficiently utilized by some carnivorous fish and even bring serious metabolic diseases. Therefore, how to improve carbohydrate utilization is an essential direction in fish nutrition research. It is well acknowledged that intestinal microorganisms play a crucial part in the host's growth, digestion, metabolism, and immunity, but the information about their roles in fish carbohydrate metabolism is very limited. Here, we review the progress of intestinal microorganisms and carbohydrate metabolism in fish, focusing on carbohydrate and fish health, carbohydrate metabolism disorders and the possible mechanisms, and the roles of intestinal microorganisms in carbohydrate metabolism and relative metabolic disease control. This review provides theoretical support for improving the utilization of carbohydrates and preventing relative metabolic diseases in fish from the perspective of intestinal microorganisms. [ABSTRACT FROM AUTHOR]

Aquaculture has become a crucial solution for addressing food scarcity worldwide, including Egypt. However, the intensification of aquaculture practices has led to water quality degradation and the emergence of new fish diseases, such as vibriosis. This study aimed to investigate the molecular typing, prevalence, pathogenicity, and environmental risk factors associated with Vibrio campbellii (V. campbellii) in cultured seabream. A total of 160 gilthead seabream, Sparus aurata (40 fish/season), along with 48 water samples (n = 12/season) were collected randomly and seasonally from private fish farms in the Suez Canal area over the course of a year for laboratory examinations. Clinical and postmortem inspections revealed characteristic signs and lesions similar to those observed in well-known vibrios infections. Bacteriological tests revealed the presence of V. campbellii strains in various internal organs. The isolated bacteria were identified morphologically, biochemically, and molecularly by targeting the 16S rRNA conserved gene. Histopathological examination was performed, providing insights into pathogen-induced tissue damage and septicemic disease progression. The prevalence of V. campbellii showed variable patterns across seasons, with higher proportions of cases in the summer. To examine the diagnostic performance of several water quality measures, the Receiver Operating Characteristic (ROC) curve analysis was performed. The results showed various levels of predictive performance for the outcome variable V. campbellii, with ammonia serving as a significant predictor for the variable of interest. The challenge results indicated a 100% survival rate in the controls, whereas the challenged group exhibited a mortality number of 6.00 ± 0.58, resulting in a survival rate of 70.00 ± 2.89%. The current study emphasizes how crucial it is to take into account seasonal parameters to comprehend the prevalence and seriousness of vibriosis in mariculture. The findings add to a better understanding of the impact of water quality on fish disease emergence and can benefit the creation of appropriate management measures to ensure aquaculture populations' health and well-being. [ABSTRACT FROM AUTHOR]

Banyuwangi Regency has high potential for vannamei shrimp farming. Vannamei shrimp farming is susceptible to disease attack. Disease monitoring serves to determine the distribution of disease in vannamei shrimp ponds. The purpose of this study was to monitor disease in vannamei shrimp pond waters of Banyuwangi Regency. This research method uses descriptive method. Monitoring of water quality parameters insitu and exitu. Disease monitoring using Real-Time PCR Quant studio 5 to detect AHPND, WSSV, EHP, and IMNV. The analysis used was descriptive analysis. The results showed that the water quality in vannamei shrimp ponds in Banyuwangi Regency was an average temperature of 25.8℃, average salinity of 33.9 g.L-1, average dissolved oxygen (DO) 7.15 mg.L-1, average pH 8.15, average ammonia 0.257 mg.L-1, average nitrite 0.04 mg.L-1, average nitrate 4.9 mg.L-1. As for the disease, there are three types, namely AHPND, EHP, and IMNV. [ABSTRACT FROM AUTHOR]

Aquaculture is now the main source of seafood in human diets and is one of its fastest‐growing industries worldwide. However, the industry is facing several difficulties, including infectious diseases, the most significant limiting factor for aquaculture expansion. The impact of diseases on aquaculture growth, fecundity, mortality rates, and marketability is profound. Hence, the ability to predict disease outbreaks is crucial to overcoming these challenges. Various infectious agents such as bacteria, viruses, fungi, and parasites can cause significant losses of fish in intensive aquaculture practices. In an aquaculture environment, the high host density coupled with restricted water flow promotes pathogen spread. Early detection of disease is crucial for farmers as mortality rates can reach as high as 100% if left untreated. Therefore, new techniques and technical solutions for disease management in aquaculture are required. In this context, data analytics technologies, such as internet of things (IoT) sensors, artificial intelligence, and machine learning, allow farmers to proactively monitor their farms and detect potential disease outbreaks before they strike. Here, we highlighted the potential of machine learning algorithms in early pathogen detection and the possibilities of intelligent aquaculture in controlling disease outbreaks at the farm level. IoT is currently a popular study topic for smarter and sustainable aquaculture, as seen by the growing interest and broad overall assumptions. Therefore, this review aims to provide comprehensive information on the various aspects and challenges associated with modern technologies for controlling pathogenic microorganisms, as well as the potential benefits of using the IoT to improve fish health and welfare in aquaculture. [ABSTRACT FROM AUTHOR]

EU Member States should ensure that they implement adequate health surveillance schemes in all aquaculture farming areas, as appropriate for the type of production. This study presents the results of applying the FAO’s Surveillance Evaluation Tool (SET) to assess the Spanish disease surveillance system for farmed fish species, which although applied previously in livestock production, is applied here to aquaculture for the first time. Overall, there were important score differences between trout and marine fish (seabass and seabream) surveillance, which were higher for trout in the following areas: Institutional (70.8% versus 50.0%), Laboratory (91.7% versus 47.2%), and Surveillance activities (75.3% versus 61.3%). For other categories, the values were lower and no significant differences were found. However, most surveillance efforts focused only on trout, for which there are EU and WOAH listed (notifiable) diseases. In contrast, for seabream and seabass, for which there are no listed diseases, it was considered that surveillance efforts should, nevertheless, be in place and should focus on the identification of abnormal mortalities and emerging diseases, for which there are as yet no standardized harmonised methodologies.

Flavobacterial diseases, caused by bacteria in the order Flavobacteriales, are responsible for devastating losses in farmed and wild fish populations worldwide. The genera Flavobacterium (Family Flavobacteriaceae) and Chryseobacterium (Weeksellaceae) encompass the most well-known agents of fish disease in the order, but the full extent of piscine-pathogenic species within these diverse groups is unresolved, and likely underappreciated. To identify emerging agents of flavobacterial disease in US aquaculture, 183 presumptive Flavobacterium and Chryseobacterium isolates were collected from clinically affected fish representing 19 host types, from across six western states. Isolates were characterized by 16S rRNA gene sequencing and phylogenetic analysis using the gyrB gene. Antimicrobial susceptibility profiles were compared between representatives from each major phylogenetic clade. Of the isolates, 52 were identified as Chryseobacterium species and 131 as Flavobacterium. The majority of Chryseobacterium isolates fell into six clades (A-F) consisting of ≥ 5 fish isolates with ≥ 70% bootstrap support, and Flavobacterium into nine (A-I). Phylogenetic clades showed distinct patterns in antimicrobial susceptibility. Two Chryseobacterium clades (F & G), and four Flavobacterium clades (B, G-I) had comparably high minimal inhibitory concentrations (MICs) for 11/18 antimicrobials tested. Multiple clades in both genera exhibited MICs surpassing the established F. psychrophilum breakpoints for oxytetracycline and florfenicol, indicating potential resistance to two of the three antimicrobials approved for use in finfish aquaculture. Further work to investigate the virulence and antigenic diversity of these genetic groups will improve our understanding of flavobacterial disease, with applications for treatment and vaccination strategies.

Effective disease management and mitigation strategies for fish diseases depend on timely and accurate diagnosis. In recent years, artificial intelligence methods—classification algorithms in particular—have become effective instruments for automating fish disease diagnosis. This paper presents two types of ensemble models: i) the baseline averaged ensemble (AE) model and ii) the novel Performance Metric-Infused Weighted Ensemble (PMIWE) model. By leveraging pre-trained models and novel ensemble techniques, we achieve a testing accuracy of 97.53%, corresponding precision, recall, and F1-score of 97%. We also bring about enhanced interpretability and trustworthiness using the Grad-CAM (Gradient-weighted Class Activation Mapping) explainable artificial intelligence (XAI) technique.

Simple Summary: Viral Encephalopathy and Retinopathy (VER) is a severe neurological disease that affects a wide range of fish species, especially at early stages of development. The disease is caused by the Nervous Necrosis Virus (NNV) and is of major global concern as no effective treatments have been described. Therefore, the objective of this study was to obtain an NNV live attenuated vaccine for sole by introducing point mutations in non-coding regions. Vaccination assays were performed on juvenile Senegalese sole by bath, intramuscular, and intraperitoneal injection, at two temperatures (18 and 22 °C); these trials revealed higher survival in vaccinated fish and poorer viral replication, while showing a significant immune response, therefore indicating that the attenuated strain is a good vaccine candidate. Viral Encephalopathy and Retinopathy (VER) is a neurological infectious fish disease that causes vacuolization and necrosis in the central nervous system, which lead to swimming abnormalities and, generally, host death in the early stages of development. VER is caused by the Nervous Necrosis Virus (NNV), a non-enveloped virus with a bisegmented and positive-stranded (+) RNA genome. The largest segment (RNA1) codes for viral polymerase while capsid protein is encoded by RNA2. The aim of this study was to explore the potential of a reverse-engineered RGNNV/SJNNV strain that harbors mutations in both 3′NCRs (position 3073 of RNA1 and 1408 and 1412 of RNA2) as an attenuated live vaccine for sole. The attenuation of this strain was confirmed through experimental infections in sole at 22 °C. Vaccination trials were performed by bath, intramuscular, and intraperitoneal injection, at two temperatures (18 and 22 °C). Our results indicate the improved survival of vaccinated fish and delayed and poorer viral replication, as well as an overexpression of immune response genes linked to T cell markers (cd4 and cd8), to an early inflammatory response (tlr7 and tnfα), and to antiviral activity (rtp3 and mx). In conclusion, our study indicates that the attenuated strain is a good vaccine candidate as it favors sole survival upon infection with the wt strain while inducing a significant immune response. [ABSTRACT FROM AUTHOR]

Simple Summary: Antibiotics have become a threat to aquaculture due to their negative impact on aquatic environments, fish, and consumers. To contribute to the research and creation of novel tools that are able to treat and control disease in fish and substitute the use of antibiotics in the aquaculture industry, this study investigates the impact of postbiotics added through feed on health parameters and disease resistance in rainbow trout. After 30 days of supplementation with postbiotics, an improvement in survival rate when facing an experimental infection with the causative agent of Red Mouth Disease was observed in rainbow trout. This research illustrates, for the first time, the positive effect of postbiotic supplementation on rainbow trout survival when challenged with Red Mouth Disease infection; in summary, this proves the suitability of the postbiotic product for the aquaculture industry and its relevance regarding the current efforts to reduce and replace the utilization of antibiotics in animal husbandry. Postbiotics are innovative tools in animal husbandry, providing eco-friendly solutions for disease management within the industry. In this study, a new postbiotic product was evaluated for its impact on the health of rainbow trout (Oncorhynchus mykiss). In vivo studies were conducted to assess the safety of the Weissella cibaria strains used in postbiotic production. Additionally, this study evaluated the impact of diet supplementation with 0.50% postbiotics on growth performance during a 30-day feeding trial; the gut microbial communities, immunomodulation, and protection against Yersinia ruckeri infection were evaluated. The strains did not harm the animals during the 20-day observation period. Furthermore, the effect of postbiotics on growth performance was not significant (p < 0.05). The treated group showed a significant increase in acid-lactic bacteria on the 30th day of the feeding trial, with counts of 3.42 ± 0.21 log CFU/mL. Additionally, there was an up-regulation of the pro-inflammatory cytokine IL-1β in head kidney samples after 48 h of feed supplementation, whereas cytokines IL-10, IL-8, INF-γ, and TNF-α were down-regulated. The findings indicate that rainbow trout fed with postbiotics saw an improvement in their survival rate against Y. ruckeri, with a 20.66% survival improvement in the treated group. This study proves that incorporating postbiotics from two strains of W. cibaria previously isolated from rainbow trout into the diet of fish has immunomodulatory effects, enhances intestinal microbial composition, and improves fish resistance against Y. ruckeri. [ABSTRACT FROM AUTHOR]

Disease outbreaks negatively affect fish production. Antimicrobial agents used in the treatment of diseases become ineffective over time because of antibiotic resistance developed by bacteria distributed in the aquaculture environment. This study was conducted for 4 months (cold period) in a fish farm to detect the fish disease, cold water streptococcosis. In the study, four brood stock showing disease signs were detected. Bacteria isolates were obtained and identified as Vagococcus salmoninarum. Antimicrobial susceptibility of V. salmoninarum was tested and antibiotic resistance gene profiles of V. salmoninarum isolates were screened. The phylogenetic relation of the isolates with the previously reported strains was evaluated. Antibiotic resistance developed by pathogenic bacteria is distributed in the aquaculture environment. The transfer of resistance genes from one bacterium to another is very common. This situation causes the antimicrobial agents used in the treatment of diseases to become ineffective over time. The disc diffusion test showed that all four isolates developed resistance to 13 (FFC30, AX25, C30, E15, CF30, L2, OX1, S10, T30, CRO30, CC2, PT15 and TY15) of the evaluated antibiotics and were about to develop resistance to six others (AM 10, FM 300, CFP75, SXT25, APR15 and TE30). Furthermore, antibiotic resistance genes tetA, sul1, sul2, sul3, dhfr1, ereB and floR were detected in the isolated strain. Moreover, the phylogenetic analysis showed that isolated V. salmoninarum strain (ESN1) was closely related to the bacterial strains isolated from USA and Jura. [ABSTRACT FROM AUTHOR]

Featured Application: The specific application of this work involves the development of an intelligent system for diagnosing and treating fish diseases in Greek fish farming. The project aims to enhance the competitiveness of Greek fish farming by addressing the increasing mortality rates attributed to unsustainable farming methods and environmental factors. The application of data mining classifiers, particularly decision trees (DTs), in predicting and categorizing fish mortality instances contributes to the development of an intelligent system for disease diagnosis and treatment. The proactive approach, supported by rigorous evaluation processes and a feature importance analysis, holds implications for sustainable aquaculture management and aligns with global sustainability initiatives. A proposal has been put forward advocating a data-driven strategy that employs classifiers from data mining to foresee and categorize instances of fish mortality. This addresses the increasing concerns regarding the death rates in caged fish environments because of the unsustainable fish farming techniques employed and environmental variables involved. The aim of this research is to enhance the competitiveness of Greek fish farming through the development of an intelligent system that is able to diagnose fish diseases in farms. This system concurrently addresses medication and dosage issues. To achieve this, a comprehensive dataset derived from various aquaculture sources was used, including various factors such as the geographic locations, farming techniques, and indicative parameters such as the water quality, climatic conditions, and fish biological characteristics. The main objective of the research was to categorize fish mortality cases through predictive models. Advanced data mining classification methods, specifically decision trees (DTs), were used for the comparison, aiming to recognize the most appropriate method with high precision and recall rates in predicting fish death rates. To ensure the reliability of the results, a methodical evaluation process was adopted, including cross-validation and a classification performance assessment. In addition, a statistical analysis was performed to gain insights into the factors that identify the correlations between the various factors affecting fish mortality. This analysis contributes to the development of targeted conservation and restoration action strategies. The research results have important implications for sustainable management actions, enabling stakeholders to proactively address issues and monitor aquaculture practices. This proactive approach ensures the protection of farmed fish quantities while meeting global seafood requirements. The data mining using a classification approach coincides with the general context of the UN sustainability goals, reducing the losses in seafood management and production when dealing with the consequences of climate change. [ABSTRACT FROM AUTHOR]

Background: Vaccinations are still the most effective means of preventing and controlling fish viral diseases, and cells are an important substrate for the production of a viral vaccine. Therefore, the rapid-stable growth and virus sensitivity of cells are urgently needed. Methods: Chinese perch brain 100th passage (CPB p100) were acclimated in a low serum with 5% FBS L-15 for 50 passages, then transferred to 8% FBS L-15 for 150 passages. Additionally, the morphology and cell type of CPB 300th passage (CPB p300) cells were identified. We analyzed the transfection efficiency and virus sensitivity of CPB p300 cells, and then optimized the conditions of ISKNV, SCRV, and LMBV multiplication in CPB cells. Results: CPB p300 cells were more homogeneous, and the spread diameter (20–30) µm in CPB p300 cells became the dominant population. The doubling time of CPB p300 was 1.5 times shorter than that of CPB p100.However, multiplication rate of CPB p300 was 1.37 times higher than CPB p100. CPB p300 cells were susceptible to ISKNV, SCRV, and LMBV, and the optimal conditions of ISKNV, SCRV, and LMBV multiplication were simultaneous incubation, 0.6 × 105 cells/cm2 and MOI = 0.1; infection at 48 h, 0.8 × 105 cells/cm2 and MOI = 0.01; simultaneous incubation, 0.7 × 105 cells/cm2 and MOI = 0.05, respectively. The time and economic costs of ISKNV, SCRV, and LMBV multiplication in CPB p300 cells were significantly reduced. Conclusions: The acquisition of CPB p300 cells laid a good material foundation for the production of ISKNV, SCRV, and LMBV vaccines. [ABSTRACT FROM AUTHOR]

Representatives of the bacterial genus Aeromonas are some of the most notorious aquaculture pathogens associated with a range of diseases in different fish species. As the world forges toward the post-antibiotic era, alternative options for combating bacterial pathogens are needed. One such alternative option is phage biocontrol. In this study, a novel podophage—JELG-KS1—infecting Aeromonas salmonicida was retrieved from wastewater along with its host strain. The genome of the JELG-KS1 phage is a 40,505 bp dsDNA molecule with a GC% of 53.42% and 185 bp direct terminal repeats and encodes 53 predicted proteins. Genomic analysis indicates that JELG-KS1 might represent a novel genus within the subfamily Studiervirinae. Podophage JELG-KS1 is a strictly lytic phage without any identifiable virulence or AMR genes that quickly adsorbs onto the surface of host cells to initiate a 48 min long infectious cycle, resulting in the release of 71 ± 12 JELG-KS1 progeny virions per infected cell. JELG-KS1 effectively lyses its host population in vitro, even at very low multiplicities of infection. However, when challenged against a panel of Aeromonas spp. strains associated with diseases in aquaculture, JELG-KS1 shows host-specificity that is confined only to its isolation strain, immediately compromising its potential for Aeromonas spp. biocontrol in aquaculture. [ABSTRACT FROM AUTHOR]

Co-infection with pathogenic microorganisms has substantial harmful effects on susceptible host organisms. It may influence disease progression and severity via synergistic and, in rare cases, antagonistic interactions. Therefore, sick fish are more prone to acquire infections and disseminate them to other neighboring species. Several studies have been conducted regarding the existence and impact of co-infections of bacteria, parasites, fungi, and viruses in different tilapia species. However, the effect and role of parasitic co-infections in farmed tilapia have not been fully addressed and need further investigation. Thus, this review aims to discuss various aspects of pathogenic parasitic and other microbial co-infections, the mode of transmission of major parasites, and the ecological impacts of the parasites affecting farmed tilapia species worldwide. Co-infections have a significant impact in aquaculture and may influence the development and severity of various fish diseases. Nevertheless, information regarding the underlying pathogenic mechanisms and microbial associations that emerge during these co-infections is scarce. In many cases, a prominent pathogen is believed to be critical and is thus recommended for treatment, while the co-infecting agents are ignored, which may worsen the case. This review also highlights other ways to raise awareness of co-infections and assist scientists and fish health inspectors in paying more attention to the natural occurrence of co-infections. This will result in further investigation and the continuous diagnosis of co-infectious events to maximize treatment practices to save tilapia that have been infected with parasites that cause co-infections. [ABSTRACT FROM AUTHOR]

Background: Formaldehyde (FA) and oxytetracycline (OTC) are the chemicals commonly used in aquaculture to prevent or treat fish diseases due to protozoa, parasites, and bacteria. Aim: The goal of the present study is to assess the liver injury and oxidative stress induced by exposure of sea bass (Dicentrarchuslabrax L) to therapeutic doses of FA (200 ml.m-3) and OTC (40 g.m-3) under the same conditions being applied in intensive aquaculture systems in Tunisia. Methods: The liver histopathological survey was achieved after 5 and 10 days of exposure to FA, OTC separately or mixed. In parallel, liver catalase activity and malondialdehyde (MDA) were measured to assess oxidative stress. Results: Results showed that treatment with FA and OTC used alone or in combinations induced liver damage as measured by sinusoid dilatation, intensive vacuolization, blood congestion, and focal necrosis. Significant elevation in catalyze activity and MDA levels were also observed in liver homogenates by the treatment (p ≤ 005). Conclusion: Combined treatment induced higher effects suggesting the critical hazards associated with FA and OTC when released to the environment. [ABSTRACT FROM AUTHOR]

Simple Summary: The purpose of this study is to evaluate veterinary records of fish diagnosed with cancer to determine the most common presentation of this disease and the efficacy of various treatments. Currently, there are no comprehensive analyses of cancer across all fish species, and this study serves to aid veterinary clinicians in the management of these patients. Fish serve an important role in society as companion animals, educational ambassadors, and research models, and advances in their standard of care benefit veterinary medicine and several other industries. This study evaluated neoplasia in fish using medical records from zoos, aquariums, and exotic animal veterinarians. The parameters evaluated included geographic location, habitat type, signalment, anatomic location of neoplasia, type of neoplasia as confirmed with histologic examination, survival time, and treatments provided for each patient. These data were entered into the Exotic Species Cancer Research Alliance (ESCRA) database. Out of 455 cases from across the United States and England, most animals submitted were from zoologic parks or aquariums (62.9%), followed by private ownership (1.5%). The percent of female (19.3%) and male (17.8%) patients were similar, and the mean age at the time of diagnosis was 99.45 months, with a range of 12 to 300 months. The species with the highest neoplasia prevalence was koi (18.5%), followed by goldfish (10.8%). The eye was the most commonly reported site for a primary neoplasm (8.4%), and the most prevalent diagnosis across all organ systems was soft tissue sarcoma (26.2%). Only 13 patients in this study (2.9%) received any form of treatment, with a mean survival time of 8.85 months post-treatment. These data demonstrate that while information related to clinical therapy of cancer in fish species is lacking, surgical excision of tumors in fish, when feasible for the patient and client, may improve patient outcomes. [ABSTRACT FROM AUTHOR]

Immunoglobulins (Igs), also termed antibodies, orchestrate host-acquired immune responses against foreign antigens, including invasive pathogens. In fish, IgM, which is present predominantly circulating in the blood, is particularly important for humoral systemic immunity and protecting the host from pathogens. The efficacy of inactivated vaccines, a major type of vaccine commonly used worldwide in fish, is directly linked to the serum antibody level; however, the timing of the appearance of systemic IgM circulating in the blood has not been determined in fish. In the present study, we examined the dynamics of serum IgM levels in juvenile Japanese amberjack Seriola quinqueradiata, using a highly sensitive sandwich enzyme-linked immunosorbent assay (ELISA) that we developed for IgM. We found that serum IgM concentration in young fish up to 72 days post-hatching (d.p.h.) (mean ± standard error of the mean [SEM]; body weight: 5.73 ± 0.38 g, standard length [S.L.]: 72.2 ± 1.94 mm) was sustained at a low level, but that the level significantly increased from 79 d.p.h. onward, reaching a mean of 84.76 ± 9.23 μg/mL at 85 d.p.h. (body weight: 14.05 ± 0.92 g, S.L.: 101.1 ± 2.07 mm). These results suggest that systemic immunity mediated by IgM is only partially matured in the early growth stage of juveniles. The present findings could help establish effective vaccination programs for infectious diseases in young fish. [ABSTRACT FROM AUTHOR]

Bacterial fish diseases are one of the challenges facing the aquaculture industry and lead to tremendous economic losses. After surveying the infected farms understudy from April 2018 to November 2019, we collected 480 samples from 12 tilapia and carp farms experiencing mortalities in Kafr El-Sheikh region of Egypt with major aquaculture production. Clinically, hemorrhages, exophthalmia, and ulceration were the most common symptoms. We then determined the frequency, bacteriological and molecular identity, antibiotic sensitivity, pathogenicity, and histopathological characteristics of pathogens. For molecular identification was used a set of specific primers (16S rRNA, 16SPSEflu, and Sin-1b). Our results showed that Aeromonas hydrophila, Pseudomonas fluorescens, and Streptococcus iniae were the most important causes. Antibiotic sensitivity test revealed that all isolates were highly sensitive to ciprofloxacin. Additionally, naturally and experimentally infected fish are the same in pathognomonic signs. Overall, a valuable tool for diagnosis is the combination of both bacteriological and molecular examination. Besides, choosing the best antibiotics by sensitivity test helps avoid drug resistance phenomenon. [ABSTRACT FROM AUTHOR]

The establishment of animal models for Parkinson's disease (PD) has been challenging. Nevertheless, once established, they will serve as valuable tools for elucidating the causes and pathogenesis of PD, as well as for developing new strategies for its treatment. Following the recent discovery of a series of PD causative genes in familial cases, teleost fishes, including zebrafish and medaka, have often been used to establish genetic PD models because of their ease of breeding and gene manipulation, as well as the high conservation of gene orthologs. Some of the fish lines can recapitulate PD phenotypes, which are often more pronounced than those in rodent genetic models. In addition, a new experimental teleost fish, turquoise killifish, can be used as a sporadic PD model, because it spontaneously manifests age‐dependent PD phenotypes. Several PD fish models have already made significant contributions to the discovery of novel PD pathological features, such as cytosolic leakage of mitochondrial DNA and pathogenic phosphorylation in α‐synuclein. Therefore, utilizing various PD fish models with distinct degenerative phenotypes will be an effective strategy for identifying emerging facets of PD pathogenesis and therapeutic modalities. [ABSTRACT FROM AUTHOR]

Praziquantel (PZQ) is a drug effective against several parasitic diseases of fish caused by Platyhelminthes. The study assesses the efficacy of selected in-feed PZQ doses in eliminating metacercariae Diplostomum pseudospathaceum in grass carp. The fish were infected with D. pseudospathaceum in laboratory conditions and subsequently treated with PZQ at daily doses of 30 (PZQ1), 50 (PZQ2), and 100 (PZQ3) mg/kg bw for seven days. The treatment trial was followed by a 23-day observation period during which the fish were parasitologically examined on days 0, 2, 8 and 23. Smaller fish were infected with a significantly higher (P < 0.05) number of metacercariae than bigger fish among three weight groups as follows: up to 7 g > 7 to 12 g > 12 g. The in-feed PZQ at doses of 30, 50 and 100 mg/kg bw for seven days was 47%, 84% and 88% effective against metacercariae D. pseudospathaceum, respectively. A significant decrease (P < 0.01) in moving and an increase (P < 0.01) in the immotile metacercariae in the eye's lens were recorded in all the trial groups on each sampling day. An increasing proportion of motile metacercariae in the post-treatment observation period was seen in PZQ2 and PZQ3, indicating a decreasing trend in the actual efficacy in an environment with no reinfection possibility. [ABSTRACT FROM AUTHOR]