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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.

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.

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.

The adequate collection of health information at the farm level is the first step in good health management. The objective of this study was to analyze how Spanish fish farms collect their census, disease occurrence, and mortality data through their farm record books and how they use them for reporting to competent authorities. Comparing and contrasting farm books between regions (autonomous communities) revealed a lack of standardization and substantial differences in the reporting. Therefore, this study points out the need to improve and standardize, at the national level, the design of fish farm record books in order to ensure the better collection of farm census data on mortality and disease occurrence, which may facilitate the production of epidemiological reports and the early detection of emerging diseases at the national level.

The spread of infectious illnesses has been a significant factor restricting aquaculture production. To maximise aquatic animal health, vaccination tactics are very successful and cost-efficient for protecting fish and aquaculture animals against many disease pathogens. However, due to the increasing number of immunological cases and their complexity, it is impossible to manage, analyse, visualise, and interpret such data without the assistance of advanced computational techniques. Hence, the use of immunoinformatics tools is crucial, as they not only facilitate the management of massive amounts of data but also greatly contribute to the creation of fresh hypotheses regarding immune responses. In recent years, advances in biotechnology and immunoinformatics have opened up new research avenues for generating novel vaccines and enhancing existing vaccinations against outbreaks of infectious illnesses, thereby reducing aquaculture losses. This review focuses on understanding in silico epitope-based vaccine design, the creation of multi-epitope vaccines, the molecular interaction of immunogenic vaccines, and the application of immunoinformatics in fish disease based on the frequency of their application and reliable results. It is believed that it can bridge the gap between experimental and computational approaches and reduce the need for experimental research, so that only wet laboratory testing integrated with in silico techniques may yield highly promising results and be useful for the development of vaccines for fish.

AbstractThe sustainable use of scarce natural resources is a significant challenge for the aquaculture industry’s future development. There are several obstacles to future expansion, including problems with fish nutrition and disease management. Aquaculture is a rapidly growing industry that faces challenges in maintaining the sustainability and environmental friendliness of production. Aquatic environments make fish especially susceptible to widespread pathogens, making disease and health management important for sustainable development. The use of probiotics has been proposed as a potential solution to these challenges. Probiotics are live microorganisms that when administered in adequate amounts, confer a health benefit on the host. In aquaculture, probiotics have been shown to improve growth rates, disease resistance, and water quality. Using probiotics to modulate intestinal microbiota is an alternative method of reducing pathogen adhesion and colonization in larval, fry, and juvenile intestines. To increase the proportion of healthy bacteria in the gut, they are administered into a fish diet or water. However, the research on the applications of probiotics in sustainable and environmentally friendly aquaculture is still not fully completed. Further research is needed to address the knowledge gap and to investigate the potential benefits and limitations of probiotics in different aquaculture systems. Areas that need to be addressed include the selection and optimization of probiotics for specific aquaculture species and production systems, the development of effective delivery methods, and the assessment of the long-term effects of probiotic use on the environment and the host. By addressing these areas, probiotics can be integrated into sustainable and environmentally friendly aquaculture practices to support the growth of the industry while minimizing its impact on the environment. This review aims to provide a comprehensive overview of the sources and standards of assortment and actions of microorganisms used in aquaculture as probiotics, whether native or commercial. Additionally, this review examines the mechanisms of action by which probiotics promote fish health and the current state of knowledge on the efficacy of probiotics in immunity, and the interchange between the reproduction and metabolism of probiotics in aquaculture. Overall, this review provides valuable insights for researchers and industry professionals seeking to effectively utilize probiotics in aquaculture. [Figure: see text]

The emerging outbreak of bacterial diseases poses a major threat to the aquaculture industry, and the abuse of antibiotics leads to the emergence of drug-resistant pathogens; hence, the development of antibacterial agents from natural resources to control and manage fish bacterial diseases has become a promising strategy. In this study, seven potential Streptomyces spp. with antimicrobial activity against fish pathogenic bacteria were isolated from the soils of different regions in China. Streptomyces termitum N-15, which showed the strongest and most stable antibacterial activity, was selected for the fish disease control experiment. Then, we investigated the effect of a basal diet and N-15 supplementation (108 ​CFU/mg diet) on growth performance, blood immune parameters (ACP and AKP), and the expression of immune genes. The results demonstrated that the ACP and AKP activities of serum were significantly increased in the N-15-supplemented group. Moreover, N-15 upregulated the expression level of Toll-like receptor 4 (TLR-4) in the kidney, liver, spleen and head kidney. The challenge test showed that supplementation with N-15 could significantly improve the survival rates of grass carp infected with A. veronii. Chalcomycin A was purified from Streptomyces termitum N-15 and found to have antimicrobial activity against fish pathogenic bacteria for the first time. Furthermore, the complete genome of S. termitum N-15 was found to consist of an 8,887,222 bp circular chromosome with 72.89% GC content and a plasmid genome, including 7744 protein-coding sequences (CDSs). The genome of S. termitum N-15 contained gene clusters for the synthesis of multiple secondary metabolites, including melingomycin, sulforaphane, oromycin, chlortetracycline, isomycin, and primycin, by antiSMASH online software. Gene cluster 1.5 revealed a chalcomycin A biosynthesis gene cluster (chmGⅠ, chmGⅡ, chmGⅢ, chmGⅣ, chmGⅤ). In summary, S. termitum N-15 and its secondary metabolites are expected to be developed into inoculants for promoting fish health in aquacultural systems.

Fish diseases in aquaculture constitute a significant hazard to nutriment security. Identification of infected fishes in aquaculture remains challenging to find out at the early stage due to the dearth of necessary infrastructure. The identification of infected fish timely is an obligatory step to thwart from spreading disease. In this work, we want to find out the salmon fish disease in aquaculture, as salmon aquaculture is the fastest-growing food production system globally, accounting for 70 percent (2.5 million tons) of the market. In the alliance of flawless image processing and machine learning mechanism, we identify the infected fishes caused by the various pathogen. This work divides into two portions. In the rudimentary portion, image pre-processing and segmentation have been applied to reduce noise and exaggerate the image, respectively. In the second portion, we extract the involved features to classify the diseases with the help of the Support Vector Machine (SVM) algorithm of machine learning with a kernel function. The processed images of the first portion have passed through this (SVM) model. Then we harmonize a comprehensive experiment with the proposed combination of techniques on the salmon fish image dataset used to examine the fish disease. We have conveyed this work on a novel dataset compromising with and without image augmentation. The results have bought a judgment of our applied SVM performs notably with 91.42 and 94.12 percent of accuracy, respectively, with and without augmentation.

This study aimed to investigate the infection of internal parasites of Dentex macrophthalmus in Syrian marine coastal waters. A total of 409 individuals were collected from Ras Al-Basit in the north to Tartus in the south, from the following research stations: Ras Al-Basit, different areas along the Lattakia beach, Jableh, and Tartous, during the period from January 2019 to December 2020. The internal organs (stomach, intestine, and body cavity) of all fish specimens were examined to detect infection with internal parasites. The third-stage larvae of the parasite Anisakis simplex, which belongs to the nematode worms, was isolated from the stomach and gonad walls of D. macrophthalmus. The number of fish infected with this worm reached 53 out of 409 fish individuals studied, with an infection rate of 12.96% and an infection intensity of 2.70 parasites per fish. This study represents the first record of Anisakis simplex isolated from the abdominal cavity of D. macrophthalmus in Syrian marine waters.

The Gram-negative bacterium A. salmonicida is the causal agent of furunculosis and used to be one of the most loss-causing bacterial infections in the salmonid aquaculture industry with a mortality rate of about 90% until the 1990s, when an inactivated vaccine with mineral oil as adjuvant was successfully implemented to control the disease. However, the use of this vaccine is associated with inflammatory side effects in the peritoneal cavity as well as autoimmune reactions in Atlantic salmon, and incomplete protection has been reported in rainbow trout. We here aimed at developing and testing a recombinant alternative vaccine based on virus-like particles (VLPs) decorated with VapA, the key structural surface protein in the outer A-layer of A. salmonicida. The VLP carrier was based on either the capsid protein of a fish nodavirus, namely red grouper nervous necrotic virus (RGNNV) or the capsid protein of Acinetobacter phage AP205. The VapA and capsid proteins were expressed individually in E. coli and VapA was fused to auto-assembled VLPs using the SpyTag/SpyCatcher technology. Rainbow trout were vaccinated/immunized with the VapA-VLP vaccines by intraperitoneal injection and were challenged with A. salmonicida 7 weeks later. The VLP vaccines provided protection comparable to that of a bacterin-based vaccine and antibody response analysis demonstrated that vaccinated fish mounted a strong VapA-specific antibody response. To our knowledge, this is the first demonstration of the potential use of antigen-decorated VLPs for vaccination against a bacterial disease in salmonids.

Bacterial infections, such as Edwardsiella tarda, can cause fish diseases. The onset of the disease is the least expected by the cultivators because it can result in economic losses. Antibiotics are commonly used by cultivators to treat fish diseases caused by E. tarda infection. However, there are some undesirable consequences due to the use of antibiotics. As an alternative to antibiotics, a natural treatment containing antibacterial properties, such as keji beling (S. crispus) leaves, can be used. The research method employed in this study was an experimental procedure with a completely randomized design that included 5 treatments, 2 controls, and 3 replications. The treatments were Treatment A (30 ppm), B (60 ppm), C (90 ppm), D (120 ppm), E (150 ppm), positive control (chloramphenicol antibiotics), and negative control (without treatment). Then, observations were conducted for 24 and 48 hours. The results showed that the crude extract of keji beling leaves inhibited E. tarda bacteria, with the largest average diameter of the inhibition zone in treatment E (150 ppm) of 7.701 0.26 mm and the lowest in treatment A (30 ppm) of 6.207 0.30mm. The relationship between the treatments formed a linear pattern with the equation y = 0.0126x + 5.979 and the coefficient of determination (R2) was 0.6268.

Abstract Phenotypic variation is suggested to facilitate the persistence of environmentally growing pathogens under environmental change. Here, we hypothesized that the intensive farming environment induces higher phenotypic variation in microbial pathogens than natural environment, because of high stochasticity for growth and stronger survival selection compared to the natural environment. We tested the hypothesis with an opportunistic fish pathogen Flavobacterium columnare isolated either from fish farms or from natural waters. We measured growth parameters of two morphotypes from all isolates in different resource concentrations and two temperatures relevant for the occurrence of disease epidemics at farms and tested their virulence using a zebrafish (Danio rerio) infection model. According to our hypothesis, isolates originating from the fish farms had higher phenotypic variation in growth between the morphotypes than the isolates from natural waters. The difference was more pronounced in higher resource concentrations and the higher temperature, suggesting that phenotypic variation is driven by the exploitation of increased outside‐host resources at farms. Phenotypic variation of virulence was not observed based on isolate origin but only based on morphotype. However, when in contact with the larger fish, the less virulent morphotype of some of the isolates also had high virulence. As the less virulent morphotype also had higher growth rate in outside‐host resources, the results suggest that both morphotypes can contribute to F. columnare epidemics at fish farms, especially with current prospects of warming temperatures. Our results suggest that higher phenotypic variation per se does not lead to higher virulence, but that environmental conditions at fish farms could select isolates with high phenotypic variation in bacterial population and hence affect evolution in F. columnare at fish farms. Our results highlight the multifaceted effects of human‐induced environmental alterations in shaping epidemiology and evolution in microbial pathogens.

In this case study, the high densities of fish in the rearing facility make an easy transfer and multiplication of specific pathogens. The limited space in which the fish are forced to live is itself a factor that overstates adaption mechanisms and can lead to the weakening of resistance to diseases. The authors presents the main parasitosis of cyprinids registered during the first period in closed recirculating aquaculture system after the transfer from open aquaculture system. These are represented by: spring viraemia of carp, ligulosis, lernaeosis, bothriocephalosis, saprolegniosis during the experimentation period of six weeks in a closed system. Results of this study shows the relationship between environmental factors and parasitosis development and the characteristics of the diseases registered in urban Recirculating Aquaculture Systems from epidemiology, pathology, etiology and diagnostics points of view. In conclusion, biosecurity measures must be applied in any kind of aquaculture activity and fish health must be monitored continuously so any treatments to be appropriate and applied as efficiently as possible.

Fish diseases have a significant negative influence on the Malaysian aquaculture industry. Since the 1980s, the sector has grown in size, which has resulted in a rise in the prevalence of infectious outbreaks affecting both freshwater and marine cultured fish species. Demand for commercially available fish vaccinations is predicted to increase as infectious disease outbreaks continue to occur. In Malaysia, aquaculture vaccine research and development (R&D) are still in its infancy, with most efforts concentrating on producing vaccines against bacterial infections, most notably streptococcosis, vibriosis, and motile Aeromonas septicemia. Despite several attempts, no homegrown vaccine has been effectively introduced into the manufacturing pipeline to date. At the moment, only three imported aquatic vaccines have received full permission, a far cry from the 314 and 60 vaccines licensed in the poultry and porcine industries, respectively. This review will describe recent findings regarding the development of aquaculture vaccines for certain fish species and diseases in Malaysia. In our opinion, R&D on fish vaccines is critical to the aquaculture industry's viability.

The aquaculture industry in the Middle East (ME) is still relatively new compared to other parts of the world, making this region highly dependent on other countries for the production of food and feed needs. Aquaculture activities in the world at current is mainly focused in China; this may be propelled by its own internal demand for seafood as determined by the United Nations Food and Agriculture Organization (FAO). Challenges faced in the ME has not been elucidated so far and the issues arising might be unique only to this region due to aquaculture being in the initial stages coupled with water access and limitations, climate and geography, in addition to pollution. This review paper will present and discuss global needs for seafood focusing later on the needs in the ME, followed by a discourse into the importance, types and challenges of aquaculture in the ME. Baseline knowledge and infrastructure to enhance knowledge is a pressing need at this stage of infancy. It is hope this sector will continue to develop, and with the support of stakeholders, aquaculture in the ME will achieve a state of independence.

Background and Aim: In 2016, the tilapia-producing farms in the department of Córdoba, Colombia, had witnessed outbreaks of disease with clinical signs compatible with those caused by the tilapia lake virus (TiLV). This study was conducted to confirm the presence of TiLV in some fish farms in the department of Córdoba. Materials and Methods: A descriptive cross-sectional study was conducted in seven farms using a non-random sampling method from July 2016 to December 2017. A total of 66 fish, including 33 healthy fish and 33 fish with clinical signs, were caught, from which 178 tissue samples of spleen, liver, and brain were collected. RNA was extracted from each organ using TRIzol®. cDNA was synthesized using a retrotranscriptase and a universal amplification primer. The polymerase chain reaction was performed using primers specific to TiLV, in which the primers were amplified in a 491 bp region in segment 3 of TiLV, and the amplicons were sequenced using the Sanger method. Results: Of the seven farms surveyed, 3 (42.85%) had TiLV in the collected fish. Of the 66 collected fish, 18 (27.27%) were infected with TiLV. The virus was detected in the brain (64.3%, 18/28), spleen (61.9%, 13/21), and liver (35.7%, 10/28). The sequences were recorded in GenBank with the codes MH338228, MH350845, and MH350846 . Nucleotide homology analyses revealed that this study's circulating strains exhibited 97% identity with the Israeli strain (GenBank KU751816.1). Conclusion: This is the first official report of TiLV in the department of Córdoba, Colombia. The circulating strains detected in this study exhibited 97% identity with the Israeli strain.

Abstract In this study, it is aimed to investigate the effects of Moringa oleifera and Sorbus domestica plant extracts on bacterial disease agents Yersinia ruckeri in aquaculture. Morphological and biochemical properties of 2 different Y. ruckeri isolates were determined. Then, Real-Time PCR analysis and gene sequencing of the isolates were identified. Phytochemicals (M. oleifera and S. domestica) and antibiotics (Oxytetracycline (OX) and Enrofloxacin (ENR)) were used together in the antibiogram test of antibiotics compared to the effect status of antibiotics. Also, the effects of phytochemicals on Y. ruckeri growth was examined comparatively by spectrophotometrically measuring at 600 nm wavelength every 2 hours according to bacterial growth densities with 10 different groups formed on TSB medium. As a result of the study, it was observed that the isolates formed Gram negative, catalase positive, oxidase negative, mobile and typical Y. ruckeri colonies. After the biochemical tests performed with Microgen ID panel, 99.85% similarity was determined. The isolates overlap with the 16S rRNA gene region after sequence analysis, and 99% of the isolates were similar in phylogenetic analysis. After the antibiogram test, Oxytetracycline and Enrofloxacin antibiotics were resistant to Y. ruckeri but the effects of phytochemicals were less on solid medium (MHA). As a result of the measurements carried out in liquid medium (TSB), it was observed that phytochemicals such as M. oliefera and S. domestica inhibit the growth of bacteria by 40-50%. As the importance of antibiotic resistance is increasing day by day, we believe that these phytochemicals will give positive results in treatment instead of using antibiotics.

Abstract Many pathogens interact and evolve in communities where more than one host species is present, yet our understanding of host–pathogen specialization is mostly informed by laboratory studies with single species. Managing diseases in the wild, however, requires understanding how host–pathogen specialization affects hosts in diverse communities. Juvenile salmonid mortality in hatcheries caused by infectious hematopoietic necrosis virus (IHNV) has important implications for salmonid conservation programs. Here, we evaluate evidence for IHNV specialization on three salmonid hosts and assess how this influences intra‐ and interspecific transmission in hatchery‐reared salmonids. We expect that while more generalist viral lineages should pose an equal risk of infection across host types, viral specialization will increase intraspecific transmission. We used Bayesian models and data from 24 hatcheries in the Columbia River Basin to reconstruct the exposure history of hatcheries with two IHNV lineages, MD and UC, allowing us to estimate the probability of juvenile infection with these lineages in three salmonid host types. Our results show that lineage MD is specialized on steelhead trout and perhaps rainbow trout (both Oncorhynchus mykiss), whereas lineage UC displayed a generalist phenotype across steelhead trout, rainbow trout, and Chinook salmon. Furthermore, our results suggest the presence of specialist–generalist trade‐offs because, while lineage UC had moderate probabilities of infection across host types, lineage MD had a small probability of infection in its nonadapted host type, Chinook salmon. Thus, in addition to quantifying probabilities of infection of socially and economically important salmonid hosts with different IHNV lineages, our results provide insights into the trade‐offs that viral lineages incur in multihost communities. Our results suggest that knowledge of the specialist/generalist strategies of circulating viral lineages could be useful in salmonid conservation programs to control disease.

Today viral fish diseases cause major losses in the world aquaculture. Pathogen spread often occurs during the transportation of fish from infected farms to the disease-free ones. Therefore, the import of fish stocking material to Russia from countries with a different epidemic situation requires risk-based monitoring and forecasting. Diagnostics is of primary importance in the complex of measures to prevent the spread of viral infections in fish. To date, laboratory diagnostics of viral fish diseases is based on pathogen isolation and its identification using serological methods which require a lot of time and are performed only in large research institutes with specialized laboratories. Molecular diagnostic methods are more sensitive and high-performance. The article presents the results of using reverse transcription polymerase chain reaction to detect a number of highly dangerous viral diseases of fish (Salmonidae). As a result of this work, primers were selected and the temperature and time conditions of the reaction were optimized for the identification of infectious hematopoietic necrosis, viral hemorrhagic septicemia and infectious salmon anemia. The results obtained during the research allowed us to establish that this diagnostic method is highly specific with analytical sensitivity to infectious salmon anemia virus of 2.5 lg TCD50/сm3, to infectious hematopoietic necrosis – 2.9 lg TCD50/сm3 and to viral hemorrhagic septicemia – 4.2 lg TCD50/ сm3. The described method was used to identify reference and field strains available at the FGBI ARRIAH Reference Laboratory for Aquaculture Diseases and isolated in different years in fish farms in the territory of the Russian Federation. The research data correlated with the results obtained from virus neutralization in cell culture and ELISA performed using commercial kits. The proposed method of RT-PCR allows to detect pathogens both in fish with pronounced clinical signs and in latent virus carriers.

The aim of this study is the identification of microbial agents recovered from 8 moribund common dentex (Dentex dentex) samples (140-200 g), determination of their antimicrobial susceptibilities and description of histopathological changes. Main clinical external and internal symptoms of bacterial haemorrhagic septicaemia cases such as fin base and liver haemorrhages, splenomegaly, accumulation of fluid in the intestines and peritoneal cavity were observed. Bacteriological samples of liver, kidney and spleen were streaked onto Marine Agar and Tryptic Soy Agar plates containing %1,5 NaCl and incubated at 22°C for 48h. Gram-positive non-motile cocci and Gram-negative motile bacillus were isolated from visceral organs. According to morphological and biochemical characteristics, isolates were identified as Micrococcus luteus and Vibrio sp. The Kirby-Bauer disk diffusion method was also performed using multidisc and all isolates were determined to be sensitive against kanamycin, oxytetracycline and flumequine. In the infected fish, general cell degenerations and necrosis in various tissues, a remarkable increase in the goblet cells of the intestines, hepatic lipidosis in the liver, hyperplasia in the gills and the presence of melanomacrophage centres in various tissues were demonstrated. As a result, here, a mixed infection in moribund fish samples was described and this is the first report on the histopathological changes of M. luteus infection in a marine fish species. This bacterium was detected as a possible pathogen of common dentex with various external, internal and histopathological damages.

Marine bio-sourced chitosan nanoparticles (CSNP) are antimicrobial and immunomodulatory agents beneficial for fish medicine. Herein, dietary CSNP was investigated for the amelioration of the systemic inflammatory responses of an induced fish model. One hundred and forty-four rainbow trout were assigned to one pathogen-free and non-supplemented group (negative control), and three challenged groups: non-supplemented (positive control), CSNP-preventive, and CSNP-therapeutic. After a feeding experiment extended for 21 days, the organosomatic indices (OSI) and molecular aspects were assessed. After a challenge experiment extended for further 28 days, CSNP-therapeutic intervention was assessed on fish survival and systemic inflammatory responses on pathology, histo-morphology, and molecular aspects. With CSNP administration, OSI nonsignificantly decreased and the relative expression of targeted inflammatory-mediator genes was significantly increased. The CSNP-therapeutic fish showed an RPS of 80% as compared to the positive control group, and CSNP-therapeutic administration retained the highest gene expression augmentation up to 28 days after the challenge. Notably, the splenic reticulin fibers framework of the CSNP-therapeutic group retained the highest integrity among the groups during the infection. After recovery, reticulin fibers density in the CSNP-therapeutic samples was significantly higher than in the negative control group, which indicates high innate immunity. Thus, CSNP showed promising biotherapeutic features enhancing fish resistance against infections.

Background: Lernaea cyprinacea was introduced in South America with cyprinids. To the best of our knowledge, this ectoparasite has not been reported in Santa Fe province (Argentina). Objective: To report Lernaea cyprinacea presence in Rhamdia quelen under hatchery conditions in Santa Fe province (Argentina). Methods: In May 2014, samples of L. cyprinacea attached to the fins and flanks of R. quelen were obtained in the Chronobiology Laboratory of the Veterinary Sciences School at Esperanza (Santa Fe, Argentina) where they were collected and identified. Results: A description of L. cyprinacea is presented along with detailed records previously reported in this and other regions. Conclusions: Presence of this parasite constitutes evidence of the introduction of exotic species through commercialization of their natural hosts and the potential pathogen colonization of natural environments, which constitutes a threat to the integrity of aquatic ecosystems.

Clarias gariepinus is widely cultured due to its tolerance to environmental extremes, high production and good feed conversion rate. This communication describes the farming practices of C. gariepinus in North and South 24 Parganas districts of West Bengal. Clarias gariepinus is cultured in ponds of 0.1–0.75 ha, where fingerlings were stocked at a density of 860–1150 cubic meter–1. The current practices of seed transportation were stressful to fish as the majority of the farmers noticed 5–10% mortalities, despite the use of antibiotics. Acclimatization of seeds was practiced by the majority of farmers before stocking. Different feeds including slaughter-house wastes and dead poultry were supplied. Multiple stocking and harvesting were a common practice. Major problems identified were insufficient feed, disease, transport, poor seed quality and lack of financial support. The survival percentage was poor, as 88% of the farmers recorded

The disruption of pathogen communication or quorum-sensing (QS) via quorum-quenching (QQ) molecules has been proposed as a promising strategy to fight bacterial infections. Bacillus spp. have recognizable biotechnology applications, namely as probiotic health-promoting agents or as a source of natural antimicrobial molecules, including QQ molecules. This study characterized the QQ potential of 200 Bacillus spp., isolated from the gut of different aquaculture fish species, to suppress fish pathogens QS. Approximately 12% of the tested Bacillus spp. fish isolates (FI). were able to interfere with synthetic QS molecules. Ten isolates were further selected as producers of extracellular QQ-molecules and their QQ capacity was evaluated against the QS of important aquaculture bacterial pathogens, namely Aeromonas spp., Vibrio spp., Photobacterium damselae, Edwardsiela tarda, and Shigella sonnei. The results revealed that A. veronii and E. tarda produce QS molecules that are detectable by the Chr. violaceum biosensor, and which were degraded when exposed to the extracellular extracts of three FI isolates. Moreover, the same isolates, identified as B. subtilis, B. vezelensis, and B. pumilus, significantly reduced the pathogenicity of E. tarda in zebrafish larvae, increasing its survival by 50%. Taken together, these results identified three Bacillus spp. capable of extracellularly quenching aquaculture pathogen communication, and thus become a promising source of bioactive molecules for use in the biocontrol of aquaculture bacterial diseases.

Climate change is expected to have a drastic effect on aquaculture worldwide. As we move forward with the agenda to increase and diversify aquaculture production, rising temperatures will have a progressively relevant impact on fish farming, linked to a multitude of issues associated with fish welfare. Temperature affects the physiology of both fish and pathogens, and has the potential to lead to significant increases in disease outbreaks within aquaculture systems, resulting in severe financial impacts. Significant shifts in future temperature regimes are projected for the Mediterranean Sea. We therefore aim to review and discuss the existing knowledge relating to disease outbreaks in the context of climate change in Mediterranean finfish aquaculture. The objective is to describe the effects of temperature on the physiology of both fish and pathogens, and moreover to list and discuss the principal diseases of the three main fish species farmed in the Mediterranean, namely gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax), and meagre (Argyrosomus regius). We will attempt to link the pathology of each disease to a specific temperature range, while discussing potential future disease threats associated with the available climate change trends for the Mediterranean Sea.

Abstract Background Antibiotic resistance is a global issue that threatens public health. The excessive use of antibiotics contributes to this problem as the genes of antibiotic resistance can be transferred between the bacteria in humans, animals and aquatic organisms. Metallic nanoparticles could serve as future substitutes for some conventional antibiotics because of their antimicrobial activity. The aim of this study was to evaluate the antimicrobial effects of silver and zinc oxide nanoparticles against major fish pathogens and assess their safety in vitro. Silver nanoparticles were synthesized by chemical reduction and characterized with UV–Vis spectroscopy, transmission electron microscopy and zeta sizer. The concentrations of silver and zinc oxide nanoparticles were measured using inductively coupled plasma-mass spectrometry. Subsequently, silver and zinc oxide nanoparticles were tested for their antimicrobial activity against Aeromonas hydrophila, Aeromonas salmonicida subsp. salmonicida, Edwardsiella ictaluri, Edwardsiella tarda, Francisella noatunensis subsp. orientalis, Yersinia ruckeri and Aphanomyces invadans and the minimum inhibitory concentrations were determined. MTT assay was performed on eel kidney cell line (EK-1) to determine the cell viability after incubation with nanoparticles. The interaction between silver nanoparticles and A. salmonicida was investigated by transmission electron microscopy. Results The tested nanoparticles exhibited marked antimicrobial activity. Silver nanoparticles inhibited the growth of both A. salmonicida and A. invadans at a concentration of 17 µg/mL. Zinc oxide nanoparticles inhibited the growth of A. salmonicida, Y. ruckeri and A. invadans at concentrations of 15.75, 31.5 and 3.15 µg/mL respectively. Silver nanoparticles showed higher cell viability when compared to zinc oxide nanoparticles in the MTT assay. Transmission electron microscopy showed the attachment of silver nanoparticles to the bacterial membrane and disruption of its integrity. Conclusions This is the first study on inhibitory effects of silver and zinc oxide nanoparticles towards A. salmonicida and A. invadans. Moreover, zinc oxide nanoparticles inhibited the growth of Y. ruckeri. In low concentrations, silver nanoparticles were less cytotoxic than zinc oxide nanoparticles and represent an alternative antimicrobial compound against A. hydrophila, A. salmonicida and A. invadans.

Background: Infectious Pancreatic Necrosis Virus (IPNV) is the etiological agent of a highly contagious disease that affects salmonids. In Chile, the second worldwide salmon producer, IPNV causes great economic loss and is one of the most frequently detected pathogens. Due to its high level of persistence and the lack of information about the efficiency of its diagnostic techniques, the National Reference Laboratory (NRL) for IPNV in Chile performed the first inter-laboratory ring trial, to evaluate the sensitivity, specificity and repeatability of the qRT-PCR detection methods used in the country. Results: Results showed 100% in sensitivity and specificity in most of the laboratories. Only three of the twelve participant laboratories presented problems in sensitivity and one in specificity. Problems in specificity (false positives) were most likely caused by cross contamination of the samples, while errors in sensitivity (false negatives) were due to detection problems of the least concentrated viral sample. Regarding repeatability, many of the laboratories presented great dispersion of the results (Ct values) for replicate samples over the three days of the trial. Moreover, large differences in the Ct values for each sample were detected among all the laboratories. Conclusions: Overall, the ring trial showed high values of sensitivity and specificity, with some problems of repeatability and inter-laboratory variability. This last issue needs to be addressed in order to allow harmonized diagnostic of IPNV within the country. We recommend the use of the NRL methods as validated and reliable qRT-PCR protocols for the detection of IPNV.

Objective of research: to present the actuality and novelty of application of fish and grass “rotation” because this allows to reveal new data on pond drainage planning which is the most effective in sanitation of the fish farm.Materials and methods: To determine the most effective cycle for the summer drying of ponds, we studied ecological and epizootological features of fishing ponds, which had been used after drying within 1 and 5 years. As research object served 8 fish ponds: 4 drained ponds under crop (40 ha), 4 – overflowed (40 ha) and filled with one-year carps (2,5-З thousand ind./ha) and silver carps (1,2-1,4 thousand ind./ha).Results and discussion: The results of comparative research on anti-epizootic efficacy of pond drying at different periodicity of 1 and 5 years with the use of fish and grass “rotation” are provided. Data on decreased invasion of fishes (carp, silver carp) by parasites, absence of causative agents of infection, improved blood indicators, increased fish production at annual pond drying (with the use of fish and grass “rotation”) compared with the pond drying of 5 year periodicity are presented. Advantages of economic efficacy of the annual frequency of pond drying are confirmed: twice increased commercial fish production; reduced expenses for purchase of food (own barley and wheat production), drugs, disinfectants, fertilizers that allow increasing economic revenue and making profit.

A total of 128 fish samples including 70 Cyprinus carpio Linnaeus, 1758, 10 Leuciscus vorax (Heckel, 1843), 40 Oreochromis aureus (Steindachner, 1864) and eight Planiliza abu (Heckel, 1843) were collected during the period from November 2016 to May 2017. Seven different localities (floating cages, earthen ponds and natural water) in Basrah were investigated. Among some detected fish diseases, whirling disease symptoms was reported for the first time in Iraq in April 2017, from two C. carpio cultured in earthen fish ponds of Marine Science Centre, University of Basrah. The infested fish were dwarfed, with abnormal big head and small body. Grossly signs of the diseases represent fins and tail deformities in addition to open ulcers and losing of scales, and necrosis of skin and muscles. Internally, fish suffered of muscles ecchymosis and vertebral deformities. Histological sections revealed that the spinal cord had healthy structure.

One of the main constraints in aquaculture production is farmed fish vulnerability to diseases due to husbandry practices or external factors like pollution, climate changes, or even the alterations in the dynamic of product transactions in this industry. It is though important to better understand and characterize the intervenients in the process of a disease outbreak as these lead to huge economical losses in aquaculture industries. High-throughput technologies like proteomics can be an important characterization tool especially in pathogen identification and the virulence mechanisms related to host-pathogen interactions on disease research and diagnostics that will help to control, prevent, and treat diseases in farmed fish. Proteomics important role is also maximized by its holistic approach to understanding pathogenesis processes and fish responses to external factors like stress or temperature making it one of the most promising tools for fish pathology research.

The aim of the work was to evaluate long-term results of studies focusing on improving methods for preventing and treating fish diseases using selected natural and syntetic immunomodulators and vaccines in fish culture. Simultaneously, attention is drawn to infectious or environmental threats against which appropriately composed immunoprophylaxis can be used in production cycles. Fish culture is intensifying in Poland and globally, which means that the role of prevention and well-designed prophylaxis is of increasing significance to the prevention and treatment of fish diseases. Currently, 33 fish species are cultured in Poland as stocking material or for production. The primary methods for preventing diseases in controlled fish culture are ensuring the welfare of fish and other prophylactic methods, including immunoprophylaxis. Many infectious and non-infectious threats that can cause direct losses and limit fish culture are present in the aquatic environment. Fish diseases generally stem from the simultaneous action of many factors that coincide and are difficult to distinguish. Pesticides (organochlorine insecticides, organophosphorus herbicides), aromatic hydrocarbons, pentachlorophenol, heavy metals, and chemotherapeutics are particularly toxic to fish. Biodegradation, which is continual in aquatic environments, is a process by which toxic and other substances that negatively affect fish become bioavailable and impact the immune system, the functioning of which is a specific bioindicator of environmental quality. Innate immunity plays a key role in the defense against disadvantageous factors, which also include pathogens. Immunomodulation methods can protect resistance mechanisms, thereby increasing disease prevention and treatment in controlled fish culture.

Purpose. The methods of molecular diagnostic (MMD) gradually become widespread in modern fish farming. MMD contain a wide variety of specific approaches, each of which has distinct limits of their possible applications and is characterized by individual peculiarities in practical performance. In addition to high sensitivity and the possibility of rapid diagnostics, the main advantage of molecular methods is to determine the uncultivated infectious agents. DNA amplification allows identifying pathogenic microorganisms at very small quantities even in the minimum sample volume. Molecular methods of diagnostic enable the determination of infection in latent or acute phases. These methods allow showing the differences between pathogens with similar antigenic structures. The current literature data on this subject usually show a methodology in the narrow context of the tasks or practical results obtained through such approaches. Thus, a synthesis of existing information on the mechanisms of action and the limits of the typical problems of basic methods of molecular diagnostics are an urgent task of fish breeding. In particular, the following description will more effectively choose one or several approaches to identify pathogens in fish. Findings. This paper reviews the basic molecular methods that are used in the world's aquaculture for diagnosis of various diseases in commercial fish species. Originality. This work is a generalization of data on the principles and mechanisms for the implementation of diagnostics based on modern molecular techniques. For each of the mentioned approaches, the most promising areas of application were shown. The information is provided in the form of a comparative analysis of each methodology, indicating positive and negative practical aspects. Practical value. The current review of modern methods of molecular diagnostic in aquaculture is focused on practical application. Generalizing and analytical information can be used when planning the work flow and differential diagnostic measures (both operational as well and preventive), and will be useful when creating complex diagnostic approaches of general and individual character.

Clarias gariepinus is widely cultured due to its tolerance to environmental extremes, high production and good feed conversion rate. This communication describes the farming practices of C. gariepinus in North and South 24 Parganas districts of West Bengal. Clarias gariepinus is cultured in ponds of 0.1–0.75 ha, where fingerlings were stocked at a density of 860–1150 cubic.m–1. The current practices of seed transportation were stressful to fish as the majority of the farmers noticed 5–10% mortalities, despite the use of antibiotics. Acclimatization of seeds was practiced by the majority of farmers before stocking. Different feeds including slaughter-house wastes and dead poultry were supplied. Multiple stocking and harvesting were a common practice. Major problems identified were insufficient feed, disease, transport, poor seed quality and lack of financial support. The survival percentage was poor, as 88% of the farmers recorded

Discusses myxozoans--metazoan parasites of marine and freshwater invertebrates and fishes. Provides examples of species that infect aquarium and warmwater species; morphology; general life cycle and transmission; methods for diagnosing infections in fish; and advice for treatment, prevention, and control.

Discusses myxozoans--metazoan parasites of marine and freshwater invertebrates and fishes. Provides examples of species that infect aquarium and warmwater species; morphology; general life cycle and transmission; methods for diagnosing infections in fish; and advice for treatment, prevention, and control.

Discusses myxozoans--metazoan parasites of marine and freshwater invertebrates and fishes. Provides examples of species that infect aquarium and warmwater species; morphology; general life cycle and transmission; methods for diagnosing infections in fish; and advice for treatment, prevention, and control.

Skin infections by Mycobacterium marinum are quite rare in our environment and, therefore, little studied. The majority of the lesions appear three weeks after traumas in aquariums, beaches and fish tanks. Lymph node drainage and systematization of the disease are rare and most lesions disappear in about three years. This case aims to show the effectiveness of the treatment used (lymecycline 150 mg/orally/day). This medication may be a new therapeutic option for the treatment of Mycobacterium marinum.

Ciguatera is a disease transmitted, particularly by fish consumption. Fishes thatcome from tropical and subtropical waters where reefs and corals abound, have moreprobability of being contaminated with the different forms of ciguatoxin and onlyhumans are poisoned when they consume contaminated fishes. The symptomatologyappear generally in the first 24 hours, in a fast way, and they are characterized forgastrointestinal, neurological and cardiovascular symptoms. In some cases alsochronic neurological, urinary and psychiatric symptoms can be presented. A possibletransmission by human milk is mentioned. Epidemiological and clinical criteria are veryimportant to do a suitable clinical impression and through instances of public health topromote the mechanisms for the definitive diagnosis of the disease by means of themicrobiological exam of the species of consumed fish. The treatment is symptomatic and it requires subsequent controls for the chronic complications. The authorities ofpublic and environmental health must look for means and methods to prevent theconsumption of fishes with high risk of being contaminated. Rev.Cienc.Biomed.2013;4(1):174-185RESUMEN:La ciguatera es una enfermedad transmitida de manera particular por la ingesta depescado. Los peces provenientes de aguas tropicales y subtropicales en donde abundanarrecifes y corales tienen mayor probabilidad de contaminarse con las diferentesformas de ciguatoxina. El hombre se intoxica cuando ingiere los peces contaminados.La sintomatología aparece en las primeras 24 horas, de forma rápida, caracterizadapor síntomas gastrointestinales, neurológicos y cardiovasculares. En muchos casosse pueden presentar síntomas crónicos neurológicos, urinarios y psiquiátricos. Se haseñalado la posible transmisión por leche materna. Los criterios epidemiológicos yclínicos son muy importantes para realizar una adecuada impresión clínica. Se debenpromover los mecanismos para el diagnóstico definitivo de la enfermedad por mediodel examen microbiológico de las especies de pescado consumido. El tratamientoes sintomático y requiere controles para identificar las complicaciones crónicas. Lasautoridades de salud pública y ambiental deben buscar medios y métodos para prevenirel consumo de pescados con riesgo de estar contaminado. Rev.Cienc.Biomed.2013;4(1):174-185

Argentina's central region includes an important area covered by shallow pampean lakes and dams. In these environments, fishing of pejerrey Odontesthes bonariensis Valenciennes, 1835 (Pisces, Atherinopsidae), the most important fresh-water fish of the country, is a relevant social activity and also a considerable economic resource. The main diseases found in this species were studied from 1992 to 2003 in the provinces of Córdoba, La Rioja and Santa Fe (30º and 35º S, 61º and 67º W). Most cases were registered in high temperature months. Lernaea sp and Aeromonas hydrophila were the etiological agents most frequently found. The trophic characteristics of the aquatic environments enhanced disease processes and caused massive death of O. bonariensis, due to complex hydrochemical interactions.A região central de Argentina possui uma importante superfície coberta por represas e lagunas pampianas. Nestes ambientes, a pesca do peixe-rei Odontesthes bonariensis Valenciennes, 1835 (Pisces, Atherinopsidae), peixe de água doce mais importante do país, é uma atividade social relevante e de significado valor econômico. Estudaram-se as principais enfermidades que afetaram esta espécie de peixe no período de 1992-2003, nas províncias de Córdoba, La Rioja e Santa Fe (30 e 35ºS, 61 e 67ºW). A maior quantidade de casos foi registrada nos meses de temperaturas elevadas. Lernaea sp e Aeromonas hydrophila foram os agentes etiológicos mais importantes. As características tróficas particulares dos ambientes aquáticos estudados foram importantes por potenciarem alguns casos, mas em outros a causa da mortandade dos peixes esteve relacionada a complexas interações hidroquímicas.

The study was carried out to assess the impact of diseases on fish production in baors of Jessore district, Bangladesh from March 2012 to January 2013. Studied baors were selected randomly from each sub-district which covered 39.22% of total baors and 71.87% baor areas in Jessore district. All the surveyed baors were affected more or less by various diseases and in 80% baors noticeable production loss occurred almost every year. The main diseases were epizootic ulcerative syndrome (EUS), dropsy, gill rot and fin rot; out breaking time ranged from November to February each year. EUS was recorded in 85% baors whereas other diseases were found in various baors at various percentages: dropsy (75%), gill rot (45%) and fin rot (55%). Conferring to the number of affected fishes, 31.25% were affected by EUS, 37.5% by dropsy, 12.5% by gill rot and 18.75% by fin rot. In the year 2012, 0.513% loss of production has occurred that designated 0.7599 million BDT. Through successful work on disease control and management, production loss may be minimized.

This document is about betanodaviruses, an emerging group of viruses infecting over 40 marine and some freshwater fish species worldwide1. It details the characteristics of these viruses, including their non-enveloped, icosahedral-shaped capsid and single-stranded, positive-sense RNA2. The document discusses the diseases caused by betanodaviruses, such as viral nervous necrosis (VNN) and viral encephalopathy and retinopathy (VER), which primarily affect the central nervous system of fish34. It also covers prevention and control measures, including good husbandry, biosecurity, and the potential use of vaccines. The document emphasizes the importance of working with fish health professionals for diagnosis and management. First published Dec. 2010.

RESUMEN Objetivo. Determinar la presencia y prevalencia de Mycobacterium spp., en granjas de tilapia nilótica (Oreochromis niloticus) en el Municipio de Champotón, Campeche, México. Materiales y métodos. La colecta de organismos se realizó en tres granjas de cultivo de tilapia nilótica del municipio de Champotón, Campeche, México. Los organismos se examinaron externa e internamente y se tomó una muestra de riñón la cual fue sembrada en forma de estría en medios de cultivo: Löwesntein-Jensen, TCBS, KF y en TSA; las placas fueron incubadas a 35°C de 24 a 48 horas, los órganos fueron fijados en formalina tamponada al 10% para ser procesados para histología de rutina para análisis posteriores. Asimismo, muestras de cultivo bacteriológico y de tejido fueron teñidas con la técnica de Ziel-Neelsen con el fin de observar la presencia de bacilos ácido-alcohol resistentes. Resultados. Los resultados obtenidos sugieren que la presencia de Mycobacterium spp., es constante y en alta prevalencia y puede ser un factor que este mermando la rentabilidad del cultivo. Conclusiones. La presencia de Mycobacterium spp., representa un riesgo para el cultivo de tilapia en el municipio de Champotón, por ser una enfermedad muy persistente y difícil de erradicar una vez ocurrido e brote de infección, por lo cual es importante llevar estudios más detallados de la presencia de este género bacteriano, así como, medidas de prevención y dispersión de este patógeno en los cultivos adyacentes.

Concomitant infections by several parasitic genera are rare, very debilitating and often lethal to fish reared under commercial breeding conditions. Were describe a multiple and concurrent parasite infestation in cultured goldfish Carassius auratus with skin damage (nodules and/or ulceration). Fish with skin lesions underwent necropsy, and the skin and gills were scraped and examined. Histopathological examination with Hematoxylin-Eosin and Giemsa stain, and an ultrastructure study using transmission and scanning electron microscopy were conducted. In the skin, we identified multiple-parasite infestations by Gyrodactylidae, Epistylis sp., Trichodina sp., Ichthyophthirius multifiliis, Tetrahymena sp. and Ichthyobodo necator,associated with epithelial cell hyperplasia and epidermal sloughing. Although no gross lesions were observed, were identified a large number of parasites in the gills (Epistylis sp., Piscinoodinium sp., Ichthyophthirius multifiliis, Trichodina sp., Apiosoma sp., Hexamitasp. and cysts of a trematode digenean). The observed trematodes were not identified. The associated microscopic lesions were epithelial hypertrophic and hyperplasic and exhibited fusion of secondary lamellae and epithelial cell detachment. This is the first description of a protozoan Vorticella sp. parasitizing goldfish in Brazil. Multiple ectoparasitism by protozoa and Platyhelminthes, with or without apparent tissue damage, can be fatal for goldfish raised on farms with poor management.