Fish Diseases In Aquaculture Research Articles

Genomic Sequence of Streptococcus salivarius MDI13 and Latilactobacillus sakei MEI5: Two Promising Probiotic Strains Isolated from European Hakes (Merluccius merluccius, L.).

Frequently, diseases in aquaculture have been fought indiscriminately with the use of antibiotics, which has led to the development and dissemination of (multiple) antibiotic resistances in bacteria. Consequently, it is necessary to look for alternative and complementary approaches to chemotheraphy that are safe for humans, animals, and the environment, such as the use of probiotics in fish farming. The objective of this work was the Whole-Genome Sequencing (WGS) and bioinformatic and functional analyses of S. salivarius MDI13 and L. sakei MEI5, two LAB strains isolated from the gut of commercial European hakes (M. merluccius, L.) caught in the Northeast Atlantic Ocean. The WGS and bioinformatic and functional analyses confirmed the lack of transferable antibiotic resistance genes, the lack of virulence and pathogenicity issues, and their potentially probiotic characteristics. Specifically, genes involved in adhesion and aggregation, vitamin biosynthesis, and amino acid metabolism were detected in both strains. In addition, genes related to lactic acid production, active metabolism, and/or adaptation to stress and adverse conditions in the host gastrointestinal tract were detected in L. sakei MEI5. Moreover, a gene cluster encoding three bacteriocins (SlvV, BlpK, and BlpE) was identified in the genome of S. salivarius MDI13. The in vitro-synthesized bacteriocin BlpK showed antimicrobial activity against the ichthyopathogens Lc. garvieae and S. parauberis. Altogether, our results suggest that S. salivarius MDI13 and L. sakei MEI5 have a strong potential as probiotics to prevent fish diseases in aquaculture as an appropriate alternative/complementary strategy to the use of antibiotics.

Characteristics of CD4-1 gene and its immune responses against Aeromonas veronii infection by activating NF-κB signaling in Qihe crucian carp Carassius auratus

CD4-1 found in bony fish contains four extracellular immunoglobulin (Ig)-like domains similar to that of mammalian CD4, which is crucial for the activation of CD4+ helper T-cell. However, there is limited knowledge regarding the molecular markers, immune functions and regulation mechanism of CD4-1 in teleosts due to their vast diversity. In this study, we cloned and characterized two isoforms of Qihe crucian carp CD4-1, designated as CaCD4-1.1 and CaCD4-1.2. We further explored their expression responses upon stimulation with Aeromonas veronii, and the regulation of their immune responses against A. veronii by NF-κB. The ORF of CaCD4-1.1 and CaCD4-1.2 cDNA encoded 477 and 466 amino acids, respectively. Both proteins contained seven conserved cysteine residues in the extracellular domain, and a CCC motif in their cytoplasm, respectively. However, CaCD4-1.1 exhibited a relatively limited similarity with CaCD4-1.2 in the ectodomain. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that the mRNA expression of CaCD4-1.1 and CaCD4-1.2 exhibited differential constitutive expression across all examined tissues. Furthermore, the expression level of CD4-1.2 was higher than that of CD4-1.1 in the gills, head kidney, and spleen of Qihe crucian carp subjected to A. veronii challenge, while it was lower in the trunk kidney. Inhibition of NF-κB activity resulted in a decrease in the expression levels of CD4-1.1 and CD4-1.2 mRNA in the gill, while inducing an increase in expression levels in the spleen, in accordance with the observed ultrastructural changes in both organs. Interestingly, the impact of NF-κB on the mRNA expression level of CD4-1.1 appears to be stronger than that of CD4-1.2. Our results suggest that CaCD4-1.1 and CaCD4-1.2 could be expressed on T cells and antigen-sampling cells that exhibit similar characteristics to mammalian M cells, respectively, and differentially regulated by NF-κB in adaptive immune responses against bacterial infection. This research contributes to a better understanding of the crucial role of CD4-1 in the immune response of Qihe crucian carp and provide novel insights for the prevention and treatment of fish diseases in aquaculture.

Molecular cloning of the hepcidin gene from crescent sweetlips (Plectorhinchus cinctus) and characterization of its encoded antimicrobial peptide

Hepcidin has been identified as an important antimicrobial peptide exerting important innate immunomodulatory activities in many fish species. In the present study, reverse transcription PCR coupled with the rapid amplification of cDNA ends was used to obtain the full-length cDNA of the crescent sweetlips hepcidin gene, which is 829 bp in length and includes an 273 bp ORF encoding a peptide with 90 amino acid residues. Sequence alignment showed a typical RXKR motif and eight conserved cysteine residues in the deduced amino acid sequences. Four disulfide bonds were predicted to form between these eight cysteines, which may stabilize the hairpin structure in hepcidin molecule. Furthermore, phylogenetic analysis showed that the deduced amino acid sequences of crescent sweetlips hepcidin had high sequence homology to hepcidins from fish species of Eupercaria. In addition, the crescent sweetlips hepcidin peptide demonstrated a strong antimicrobial activity in vitro against several types of pathogenic bacteria in fish. In conclusion, the obtained results suggested that crescent sweetlips hepcidin possessed the typical structure similar to other fish hepcidins and had strong antibacterial activity, which showed great potential in the prevention of fish diseases in aquaculture.

The Co-Isolation of Lactic Acid Bacteria (LAB) and A Related Pathogenic Strain from Pangasius Nasutus

Catfish species Pangasius nasutus, or locally known as Patin Buah is one of a popular aquaculture product in Malaysia. Probiotic strain is an attractive alternative to conventional antibiotics in managing aquaculture diseases. Pangasius can be a source of bacterial strain in developing suitable probiotic useful in Pangasius rearing. This study highlights on the isolation of LAB strains from the selected tissues from P. nasutus which are the heart, stomach, and intestines. These strains were subjected to morphological, biochemical, and genotypic characterisations. Three different strains were isolated from fish tissues, H-Hn from heart; S-Hn from stomach; and I-Sk from intestine. Biochemical characterisation were consistent with ribosomal rRNA sequencing, in which strain H-Hn (acc. No. MW504962) is highly similar (100%) to Lactococcus lactis, and both I-Sk (MW504964) and S-Hn (MW504963) are similar (99%) to Lactococcus garvieae. All strains appeared to be non-spore forming, non-motile, Gram-positive coccus, catalase and citrate negative, and fermenting sugar. Unlike H-Hn, both H-Sk and I-Sk strains were able to grow at 6.5% NaCl and at higher temperature (45°C). The antimicrobial properties were assessed using agar disk diffusion assay against several indicator organisms (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus and Vibrio parahaemolyticus). These strains exhibited varying degree of inhibitory properties against the indicator organisms. Strain H-Hn inhibited E. coli and V. parahaemolyticus. Meanwhile, strains I-Sk and S-Hn showed a rather broad-spectrum inhibition. From P. nasutus, other L. lactis strain, a pathogenic species from L. garvieae could also be found especially in their gut tissues. The presence of L. garvieae in commercial P. nasutus should raise some concern to those who like to consume this fish. Meanwhile, the LAB strains isolated has probiotics potential that can be commercially used in the managing fish diseases in aquaculture.

A CNN-OSELM Multi-Layer Fusion Network With Attention Mechanism for Fish Disease Recognition in Aquaculture

The increasing global population has escalated the demand for fish products. This calls for a stable supply which can only be met through improved aquaculture practices. The automatic recognition of fish diseases from diseased underwater images is one of such practices that aims to control disease, improve fish production and optimize profits. However, due to lack of public fish disease dataset, there has been limited research towards fish disease recognition. Moreover, due to low quality of underwater images and complex underwater environments, traditional hand-designed feature extraction methods or convolutional neural networks (CNNs)-based classifiers cannot adequately recognize fish diseases in real underwater scenes. Therefore, this paper proposes a novel hybrid approach based on multilayer fusion, attention mechanism and online sequential extreme learning machine (OSELM) to recognize fish diseases in aquaculture. We further compare the classification performance of the proposed model with baseline, attention-based, ConvNeXt and Swin transformer models. Feature extraction is enhanced by integrating same level features and focusing on salient features for fish disease recognition. The characteristic information of fish disease is refined by using strongly discriminative features of the infected fish regions and weakening regions of low interest using convolutional block attention module (CBAM). The module is added to the multilayer fusion network to sequentially infer attention maps along the channel and spatial dimensions for every intermediate feature map. Fish disease recognition is then done using OSELM for faster learning and improved classification performance. The models are trained, validated and tested on a custom dataset with image samples collected from various internet sources. The proposed method achieves 94.28% of accuracy, precision of 92.67%, recall of 92.17% and 92.42% of F1- score on dataset with background elimination. The proposed method can be used for fish disease identification in complex underwater environments in aquaculture.

Capsalid monogeneans of fishes from the Seto Inland Sea, Japan: Description of Benedenia kobudai n. sp. parasitic on Semicossyphus reticulatus (Perciformes: Labridae)

The Seto Inland Sea, the largest inland sea in Japan, is a rich fishery with high biodiversity and productivity. Monogeneans have been studied for more than 120 years, and 58 nominal species have been recorded in the Seto inland Sea. This study provided DNA information on five species of Benedenia sensu lato (Capsalidae) from marine fishes from the sea, and one of them, Benedenia kobudai n. sp., is described from Semicossyphus reticulatus (Perciformes: Labridae). This new species differs from the other congeners by the hooded appearance between the anterior attachment organs, the morphology of the penis, the absence of the lobe near the vaginal pore and the common genital pore, the position of the vaginal pore, the germarium lying near the slightly hexagonal testes, the morphology of the haptor, and the shape and position of the hamuli. Phylogenetic analysis showed B. kobudai n. sp. in a separate clade from the other Benedenia species, B. epinepheli, B. hoshinai, B. sekii, and B. seriolae collected from the sea. Each of the newly provided DNA sequences (28S rDNA, ITS1‐5.8S-ITS2, cox1) of the above four species are based on specimens obtained from the type hosts and/or type localities and are considered important for future taxonomic re-examination and confirmation of the reliability of the registered sequences. Furthermore, these four species are important causes of fish diseases in aquaculture, and it is expected that information on the distribution, host range, and occurrence of fish diseases for each capsalid secured by molecular identification will be accumulated.The Life Science Identifier (LSID): urn:lsid:zoobank.org:pub:26C15D17-CFD1-450D-9FCE-EFFF692D2133.

Fish Disease Detection Using Image Based Machine Learning Technique in Aquaculture

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.

Dietary supplementation of salidroside increases immune response and disease resistance of crucian carp (Carassius auratus) against Aeromonas hydrophila

Some medicinal plants have been known as immunostimulants, and the medicinal plants extract has been used to control the outbreak of the disease in aquaculture for many years. In this study, a total of 270 crucian carp (30 ± 5 g) were randomly distributed in 9 aquaria (55 cm l × 40 cm w × 50 cm h) and divided into three feeding groups including 0 (Control), 50 mg kg−1 (Diet A) and 100 mg kg−1 (Diet B) of salidroside. The expression of immune-related genes (IL-1β, TNFα, MYD88, CXCL-8, TGF-β, and IL-11) in the kidney had a significant increase when the crucian carp fed with Diet B for 4 weeks (P < 0.05). Meanwhile, the expression of IL-1β, TNFα, and CXCL-8 in the spleen was significantly up-regulated when the fish fed with Diet B (P < 0.05). Higher serum alkaline phosphatase (AKP) activity, catalase (CAT) activity, superoxide dismutase (SOD) activity, and complement C3 content were found in the fish which fed with salidroside-supplemented diet. Our results also proved that fish fed with salidroside-supplemented diet for four weeks, especially at a concentration of 100 mg kg−1 diet, improved the protection of crucian carp against A. hydrophila. The amount of A. hydrophila in the kidney and spleen was significantly decreased in salidroside-supplemented diet groups (P < 0.05). In conclusion, the present results demonstrate that the addition of salidroside for four weeks can improve the immune response of crucian carp and increase the protection against the pathogen, especially at the concentration of 100 mg kg−1 diet. The protective effect of the salidroside to the crucian carp could be used as alternatives to antibiotics for controlling fish diseases in aquaculture.

Zebrafish as a Model for Fish Diseases in Aquaculture.

The use of zebrafish as a model for human conditions is widely recognized. Within the last couple of decades, the zebrafish has furthermore increasingly been utilized as a model for diseases in aquacultured fish species. The unique tools available in zebrafish present advantages compared to other animal models and unprecedented in vivo imaging and the use of transgenic zebrafish lines have contributed with novel knowledge to this field. In this review, investigations conducted in zebrafish on economically important diseases in aquacultured fish species are included. Studies are summarized on bacterial, viral and parasitic diseases and described in relation to prophylactic approaches, immunology and infection biology. Considerable attention has been assigned to innate and adaptive immunological responses. Finally, advantages and drawbacks of using the zebrafish as a model for aquacultured fish species are discussed.

Antimicrobial activity of Pseudomonas monteilii JK-1 isolated from fish gut and its major metabolite, 1-hydroxyphenazine, against Aeromonas hydrophila

The application of antibiotics in aquaculture poses a huge hidden danger to aquatic products and water environment safety. Thus, the aim of this study was to isolate probiotics that can replace antibiotics and antagonize Aeromonas hydrophila from the gut of the grass carp, and then explore the main antibacterial substances of this bacteria. Pseudomonas monteilii JK-1 was isolated from the gut of grass carp and showed significant inhibition on A. hydrophila. The safety assessment revealed that the isolated P. monteilii JK-1 was not toxic to grass carp and did not exbibit hemolytic activity on sheep blood agar plates. Disc-diffusion assays using a panel of antibiotics showed that JK-1 was susceptible to selected antibiotics. In vitro study indicated that strain JK-1 can survive at pH 6.5–7.5, and tolerate bile up to 0.5% concentration. The trial test showed dietary supplementation of JK-1 significantly improved the resistance of grass carp against A. hydrophila, and the cumulative survival rate increased by 40% compared with the control group. 1-Hydroxyphenazine isolated from the metabolite of P. monteilii JK-1, had a good effect in against A. hydrophila in vitro and in vivo. The minimum inhibitory concentration of 1-hydroxyphenazine against A. hydrophila was 31.25 μg/mL. In vitro antimicrobial assays of 1-hydroxyphenazine showed that 1-hydroxyphenazine at 100, 250 μg/mL inhibited the growth of A. hydrophila after 6 and 4 h, respectively. Grass carp inoculated with A. hydrophila and treated by intraperitoneal application of 1-hydroxyphenazine had a survival rate of 75% compared with that of untreated fish (35%, 30%). These results indicate the protective effect of the P. monteilii JK-1 and 1-hydroxyphenazine against A. hydrophila could be used as alternatives to antibiotics for controlling fish diseases in aquaculture.

Penerapan teknologi budidaya ikan baung (Mystus nemurus CV) di kolam dan keramba

Tujuan dari kegiatan pengabdin kepada masyarakat ini untuk memberikan ilmu dan teknologi kepada para anggota Kelompok Pembudidaya Ikan Alam Bendungan Desa Sungai Paku, Kecamatan Kampar Kiri, Kabupaten Kampar dalam menyelesaikan permasalah yang ditemukan selama ini, terutama tentang teknologi budidaya ikan baung di kolam dan keramba. Metode yang digunakan dalam kegiatan ini adalah metode ceramah, diskusi dan demonstrasi langsung. Hasil evaluasi perubahan pengetahuan diperoleh 14 orang (70%) telah dapat menyerap materi yang diberikan dengan predikat sangat baik, 3 orang (15%) dapat menyerap materi yang diberikan dengan predikat baik, 2 orang (10%) dapat menyerap materi yang diberikan dengan predikat cukup, dan hanya 1 orang (5%) dapat menyerap materi yang diberikan dengan predikat kurang serta tidak ditemukan peserta yang memperoleh predikat kurang sekali. Hasil evaluasi keterampilan menunjukkan bahwa peserta kegiatan telah dapat mempraktekkan materi yang diberikan terutama tentang pembuatan pakan ikan (pellet) dan cara mengatasi penyakit yang menyerang ikan baung dalam budidaya. Sedangkan hasil evaluasi dampak menunjukkan bahwa kegiatan ini telah dirasakan menfaatnya oleh anggota kelompok tani yang ada, terutama dalam penyediaan pakan ikan (pellet) dan mengatasi ikan yang terserang penyakit dalam budidaya.

Bitter peptides from enzymatically hydrolyzed protein increase the number of leucocytes and lysozyme activity of large yellow croaker (Larimichthys crocea)

The large yellow croakers (Larimichthys crocea) are mainly present in the Chinese coast and near seas with high economic importance, but vulnerable to many diseases, especially in the breeding and aquaculture. The purpose of this research was to boost the innate immune system of the large yellow croaker by administering bitter peptides into their peritoneal cavity. Total 120 Juvenile of large yellow croakers in very even weight of 60 g were divided into 4 different groups in 200/300 L of water tank, respectively. Fish growth were observed for 3 months before and after different treatments. The bitter peptides from pepsin hydrolysis were applied because they possess the highest bitter sensory scores. The blood of fish from the different groups was collected and tested for different immune parameters to evaluate the effectiveness of bitter peptides as immune stimulants after administration for 8 weeks. The average ratio of leukocytes/total blood cells (%) for control was found at 14.6%, for the low dose of bitter peptides 0.6 mg/fish was at 29.3%, for middle dose of 1.2 mg/fish was at 35%, and high dose of 2.4 mg/fish was at 30%. The lysozyme assay showed that the OD (optical density) units of relative progress lysis activity at 60 min were 0.17, 0.101, 0.307 and 0.198, respectively. Similarly in the same order as in phagocyte assay, most importantly the middle dose (1.2mg/fish) gave the highest survival rate throughout the assay. The results showed that bitter peptides can be used as immune boosters for the yellow croakers and the optimum dose was 1.2 mg/fish due to both leukocytes and lysozyme activity in the treated samples increased significantly compared with the control group. According to the results obtained, we suggest that the incorporation of middle dose of bitter peptides into fish feeds may reduce the fish diseases in aquaculture, at least for large yellow croakers.

Teleosts Genomics: Progress and Prospects in Disease Prevention and Control

Genome wide studies based on conventional molecular tools and upcoming omics technologies are beginning to gain functional applications in the control and prevention of diseases in teleosts fish. Herein, we provide insights into current progress and prospects in the use genomics studies for the control and prevention of fish diseases. Metagenomics has emerged to be an important tool used to identify emerging infectious diseases for the timely design of rational disease control strategies, determining microbial compositions in different aquatic environments used for fish farming and the use of host microbiota to monitor the health status of fish. Expounding the use of antimicrobial peptides (AMPs) as therapeutic agents against different pathogens as well as elucidating their role in tissue regeneration is another vital aspect of genomics studies that had taken precedent in recent years. In vaccine development, prospects made include the identification of highly immunogenic proteins for use in recombinant vaccine designs as well as identifying gene signatures that correlate with protective immunity for use as benchmarks in optimizing vaccine efficacy. Progress in quantitative trait loci (QTL) mapping is beginning to yield considerable success in identifying resistant traits against some of the highly infectious diseases that have previously ravaged the aquaculture industry. Altogether, the synopsis put forth shows that genomics studies are beginning to yield positive contribution in the prevention and control of fish diseases in aquaculture.

Immunomodulation with Probiotics Against Aeromonas veronii in Grass Carp (Ctenopharyngodon idellus)

Aeromonas comprisea wide range of opportunistic bacteria that cause septicemia (blood poisoning)in fish.Withexpandingaquaculture, myriad methods have been used to combat these pathologiesincludingprobiotics and plant extracts which canpotentiallyaddress these diseases without harmingthe environment. Inthis study, four strains of opportunistic pathogens were isolated from diseased fish, thenmolecular identification of 16SrDNA was performed. Results identifiedthe four strains asAeromonas veronii, Shewanella sp., Bacillus cereus, and Aeromonas salmonicida. Experimental trialsrevealed that A.veroniiwas the primary strain. Multiple virulence-related factors were discovered, includingaerolysin (Aer), cytotoxic enterotoxin (Act), and the outer membrane protein (OmpAII).Thesewere foundonly in A.veronii. LC50 in grass carp was 3.6×104CFU/mLover 96 h, whereas the safe concentration was 9.11×103CFU/mL.Grass carp were challenged with 3 differentconcentrations of A.veronii. Following a 48h incubation period they were treated for 24 h, 48 h, and 72 h with 8.1×106CFU/mLconcentrations.The expression ofInterleukin-8(IL-8)andTumor Necrosis Factor-α(TNF-α)was up-regulated in the kidney, liver, spleen, and heart using qRT-PCR. Simultaneously, enzyme activity involving Pyruvate Kinase(PK),Alkaline Phosphatase(AKP), Alanine aminotransferase (ALT),Succinate Dehydrogenase (SDH), and Lysozyme (Lsz)inserum and liver tissues was significantly up-regulated.We found that probiotics enhancedgrowth of grass carp, improvedhealth status,and was beneficial in reducing the prevalence of this disease. Subsequent to feeding mixed probiotics,IL-8 and TNF-α geneexpression was significantly lower (p&gt;0.05)than inthe infected group,at 16 and 31 days. Expression of these genes in the liver, spleen, and intestines of healthy grass carp fed probiotics wassignificantly up-regulated in contrast to grass carp fed a basal diet (p&lt;0.05).Our results suggestthat use of probiotics as immune stimulator may improve the control of fish diseases in aquaculture.

Antibacterial Activities of Metabolites from Platanus occidentalis (American sycamore) against Fish Pathogenic Bacteria.

One approach to the management of common fish diseases in aquaculture is the use of antibiotic-laden feed. However, there are public concerns about the use of antibiotics in agriculture and the potential development of antibiotic resistant bacteria. Therefore, the discovery of other environmentally safe natural compounds as alternatives to antibiotics would benefit the aquaculture industries. Four natural compounds, commonly called platanosides, [kaempferol 3-O-α-L-(2″,3″-di-E-p-coumaroyl)rhamnoside (1), kaempferol 3-O-α-L-(2″-E-p-coumaroyl-3″-Z-p-coumaroyl)rhamnoside (2), kaempferol 3-O-α-L-(2″-Z-p-coumaroyl-3″-E-p-coumaroyl)rhamnoside (3), and kaempferol 3-O-α-L-(2″,3″-di-Z-p-coumaroyl)rhamnoside (4)] isolated from the leaves of the American sycamore (Platanus occidentalis) tree were evaluated using a rapid bioassay for their antibacterial activities against common fish pathogenic bacteria including Flavobacterium columnare, Edwardsiella ictaluri, Aeromonas hydrophila, and Streptococcus iniae. The four isomers and a mixture of all four isomers were strongly antibacterial against isolates of F. columnare and S. iniae. Against F. columnare ALM-00-173, 3 and 4 showed the strongest antibacterial activities, with 24-h 50% inhibition concentration (IC50) values of 2.13 ± 0.11 and 2.62 ± 0.23 mg/L, respectively. Against S. iniae LA94-426, 4 had the strongest antibacterial activity, with 24-h IC50 of 1.87 ± 0.23 mg/L. Neither a mixture of the isomers nor any of the individual isomers were antibacterial against isolates of E. ictaluri and A. hydrophila at the test concentrations used in the study. Several of the isomers appear promising for the potential management of columnaris disease and streptococcosis in fish.

Identification and characterization of a bacteriocin produced by an isolated Bacillus sp. SW1-1 that exhibits antibacterial activity against fish pathogens

The selected isolate, Bacillus sp. SW1-1 showed antibacterial activity against both Gram-positive and Gram-negative bacteria involved in fish diseases, including Edwardsiella tarda, Streptococcus iniae, S. parauberis, Vibrio anguillarum, and V. harveyi. The Maximum bacteriocin production was observed at 30°C after 24 h with brain heart infusion medium (pH 7.0). The bacteriocin SW1-1 was purified by 50% ammonium sulfate precipitation, followed by HiPrep diethylaminoethyl 16/10 FF and Sephacryl S-100 High resolution column chromatography. The substance was characterized as a bacteriocin-like inhibitory substance with a molecular mass of 38 kDa. Bacteriocin SW1-1 was sensitive to the proteolytic action of pepsin, trypsin, chymotrypsin, and protease types I and XIV, and relatively heat labile, despite the fact that bacteriocin activity was still detected after heating at 100°C for 30 min. The activity of bacteriocin SW1-1 was stable in the pH range of 2.0–11.0, and relatively unaffected by organic chemicals. The bacteriocin SW1-1 had a bacteriolytic mechanism, resulting in cell wall degradation of E. tarda. These characteristics indicate that this bacteriocin may be a potential candidate for alternative agent to control important pathogens of fish diseases in aquaculture.

Efficiency of phage cocktails in the inactivation of Vibrio in aquaculture

Abstract Aquaculture is one of the fastest growing sectors in the world, having a very important role in the economy. However, the losses associated with bacterial infections such as vibriosis, lead to huge economic costs. The regular use of antibiotics in aquaculture has resulted in the development of resistant strains, which have contributed to the inefficacy of antibiotics. To reduce the risk of the development and spreading of microbial resistance and to control the fish diseases in aquaculture, alternative strategies must be developed. Phage therapy can be an eco-friendly alternative to prevent and control pathogenic bacteria in aquaculture. However, phage bacterial resistance is already well documented but the use of phage cocktails can overcome this drawback. The aim of this study was to evaluate the efficiency of cocktails of two and three phages of Vibrio parahaemolyticus (VP-1, VP-2 and VP-3) to control Vibrio in aquaculture. All phages were effective against V. parahaemolyticus, however, the VP-3 phage was the most efficient one (additional reduction of more 2 log when compared with the other two phages). The use of cocktails with two and three phages was significantly more effective (reductions of 4 log after 2 h) than the use of VP-1 and VP-2 phages alone (reductions of 0.8 log after 2 h), however, the efficiency of VP-3 phage was similar for the phage alone and for the phage in the cocktails (reduction of 3.8 log and 4.2 log for VP-3 phage alone and in cocktails, respectively, after 8 and 6 h). All phages remained viable for a long time (at least 5–7 months) in marine water. The VP-3 phage presented a larger burst size and a shorter latent period (42 and 40 min, respectively) than the other two phages (9 and 120 min and 15 and 90 min, respectively, for VP-1 and VP-2 phages). Overall, the use of phage cocktails of two or three phages increased the efficiency of phage therapy against Vibrio (more efficient and faster bacterial inactivation), delaying the development of resistance by the bacteria and the use of Vibrio phages with high burst sizes and short lytic cycles also increases the efficiency of phage therapy.

In vitro and in vivo efficacy of garlic compounds against Gyrodactylus turnbulli infecting the guppy (Poecilia reticulata)

Traditional compounds used to treat fish diseases in aquaculture and the ornamental fish industry (such as formalin and malachite green) can be more toxic to the hosts than their parasites. With the reviviscence in the use of herbal products, various botanicals have been heralded as cures for particular pathogens, but the efficacy of these compounds for parasitic worms is questionable. Here, we tested a range of garlic (Allium sativum) products against a major aquarium pathogen, Gyrodactylus turnbulli, infecting the guppy (Poecilia reticulata). All garlic products significantly reduced parasite mean survival time in vitro, from 13h to <1h. In fully randomised trials, the number of parasites was also significantly reduced on infected fish exposed to garlic from different sources. Two garlic treatments (minced and granule forms) reduced worm burdens by 66% and 75% after three doses, whereas Chinese freeze-dried garlic and allyl disulphide were 95% effective after a single application. In fact, Chinese freeze dried garlic was equally effective as Levamisole, a licensed livestock dewormer that is highly effective against G. turnbulli but not routinely prescribed for use in fish; hence, garlic may be a potential alternative treatment for gyrodactylosis.

Tolerance of signal crayfish (Pacifastacus leniusculus) to Persteril 36 supports use of peracetic acid in astaciculture

Peracetic acid (PAA) is useful in treating a wide variety of serious fish diseases in aquaculture. As no information on PAA toxicity to crayfish is available, we conducted acute toxicity tests of Persteril 36, a commercial PAA-containing product, on three age/size classes of signal crayfish, Pacifastacus leniusculus. Results confirmed high tolerance of the target species to this product, expressed as a 96h LC50 of 77.3±1.0mgL−1 PAA in adults and low post-treatment mortality in 9month old juveniles. As PAA concentrations successfully applied in aquaculture are generally 2.0mgL−1 or lower, PAA can be recommended for use in astaciculture. After necessary evaluations, uses might include limiting spread of crayfish plague, treating saprolegniosis on artificially incubated crayfish eggs, and avoiding translocations of further crayfish-related non-native species when introducing crayfish or stocking them in closed culture systems.

Remarks on an increasing resistance of fishpathogenic and facultative-fishpathogenic bacteria in lower saxony (FRG).

Increasing resistance of specific-fishpathogenic and facultative-fishpathogenic bacteria against the main drugs licensed in Germany.With an average of yearly 600 examined cases-including the whole range of additional virological-, bacteriological-, histological-, water quality and residual. tests-the Fish Health Service (FHS) of Hannover of the Northern Federal State of LOWER SAXONY reached within the last years some representative experience dealing with the control and therapy of fish diseases in aquaculture. The control of the three notifiable viral epidemics of freshwater fish presently included in the pertinentlegislation (Animal Epidemics Act) of the FRG-VHS, IPN and SVC-is the competence of the STATE FISH EPIDEMICS CONTROL SERVICE OF LOWER SAXONY from which the FHS mentioned above is a part. The therapy of bacterial diseases-essentially Aeromonas salmonicida infections (Furunculosis/Salmonids; Erythrodermatits/Cyprinids), vibriosis, from 1981 on increasingly Enteric Redmouth Disease/ERM (with an unexpected peak in late winter-, spring and summer 1984) as well asthe mainly environment dependent-sometimes with septicemic development of the whole range of ubiquitous facultative-fishpathogenic bacteria from the aquatic environment-developed rather unprob lematic and successful in Lower Saxony for many years. From 1981 on a change in this situation with concomitant increasing resistance of specific-fishpathogenic as well as facultative-fishpathogenic bacteria. against the main drugs licensed in the FRG and used in the control of freshwater fish diseases mainly through medicated feed is observed. The bacterological examination with antibiogramme proved indispensable. In the FRG the presently licensed drugs for treatment of bacterial infections in fish are Chloramphenicol, Chlor- and Oxitetracycline, Furazolidone, Trimethoprim/Sulfadimethoxine and Nifurpracine. In the FRG Chloramphenicol was forbidden for use in domestic animals (homoeotherms) for human consumption in April 1984. It is to assume that Chloramphenicol will be withdrawn for use in fish soon. Only in few individual cases and strictly controlled by the veterinary authorities some otherdrugs can be experimentally tested under prescription and strict supervision of a veterinarian specialized in fish diseases and aquaculture. Besides the substances mentioned above antibiogrammes are routinely carried out with Oxolinic acid, “Lincospectin” (Lincomycine + Spectinomycine 1 : 2), Ampicilline, Erythromycine and very recently Flumequine.The results of 596 FHS-cases from which in 289 the bacteriological examination proceed necessaryfrom them in 162 cases the antibiogramme was feasible-carried out within the frame of the work of the FHS from January 1983 to May 1984 are discussed-, the increased resistance showed-, the effectivity and/or uselessness of some of the drugs presented. Flumequine, Oxolinic acid, Lincospectine (not yet licensed in the FRG) and last but not least the tetracyclines showed promising. The finding of few Aeromonas salmonicida subsp. salmonicida isolates completely resistant against the drugs licensed in the FRG may involve further serious problems as well as cases of total failure of therapy carried out in strict accordance with the antibiogramme if a chronic viral infection is present in the background-as e.g. observed with ERM concomitant to VHS. The results of a first field trial with Oxolinic acid in a rainbow trout population during summer of 1984 are shown. As a main result of this trials it is recommended to 86 enlarge the presently narrow frame of drugs licensed for fish in the FRG by at least two of the compounds tested: Oxolinic acid and Flumequine, or Oxolinic acid and Lincospectin; and to delete Ampicilline which was included in a pertinent priority list in 1982.