Diseases In Aquaculture Research Articles

Expression of immuno-transcriptome response in red hybrid tilapia (Oreochromis sp.) hindgut following vaccination with feed-based bivalent vaccine.

Streptococcosis and aeromoniasis are the main obstacles to sustainable tilapia production. Vaccination offered an effective method to control microbial infections. Previously, a feed-based bivalent vaccine (FBBV) containing killed whole organisms of Streptococcus agalactiae and Aeromonas hydrophila mixed with 10% palm oil was successfully developed, which provided good protection against streptococcosis and aeromoniasis in Oreochromis sp. However, the mechanisms of immunities in vaccinated fish still need clarification. Here, the hindgut transcriptome of vaccinated and control fish was determined, as the gut displays higher affinity towards antigen uptake and nutrient absorption. The efficacy of FBBV to improve fish immunity was evaluated according to the expression of immune-related genes in the vaccinated fish hindgut throughout the 8-week experimental period using RT-qPCR. The vaccinated fish hindgut at week 6 was further subjected to transcriptomic analysis due to the high expression of immune-related genes and contained killed whole organisms. Results demonstrated the expression of immune-related genes was in correlation with the presence of killed whole organisms in the vaccinated fish hindgut. Transcriptomic analysis has allowed the prediction of robust immune-related pathways, including innate and adaptive immunological responses in vaccinated fish hindgut than control fish. Pathways related to the regulation of lipid metabolism and modulation of the immune system were also significantly enriched (p ≤ .05). Overall, results offer a fundamental study on understanding the immunological response in Oreochromis sp. following vaccination with the FBBV pellet and support further application to prevent bacterial diseases in aquaculture.

Isolation and Characterization of a Novel Aeromonas salmonicida-Infecting Studiervirinae Bacteriophage, JELG-KS1.

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

Effect of Dietary Supplementation with Lactiplantibacillus plantarum I On Queen Scallop Aequipecten opercularis Under Simulated Climate Change Conditions

Abstract This study examined the effects of dietary supplementation of queen scallop Aequipecten opercularis with an indigenous strain of lactic acid bacteria (LAB), Lactiplantibacillus plantarum I, previously isolated from its digestive tract, on gut microbial populations and growth rates during cultivation under simulated climate change conditions (pH 7.8, T = 16 ± 2 °C). After one month of feeding, the results showed a noticeable reduction in aquaculture diseases causing pathogens while maintaining sufficient viable Lpb. plantarum I cells. A higher pH and temperature resulted in higher growth rates, measured by the weight and length of scallops, compared to the control group. The results obtained shed light on the influence of the addition of lactic acid bacteria on the growth of bivalve mollusks under normal and climate change conditions, and provide control of pathogenic microorganisms. In the context of climate change, host-pathogen interactions need to be recognized and put under control by applying natural solutions to minimize the environmental footprint.

Impact of bacteriocins on multidrug‐resistant bacteria and their application in aquaculture disease prevention and control

AbstractAquaculture plays an important role in meeting human demand for animal protein. Disease is a critical factor that restricts the green and healthy development of aquaculture. Intensive aquaculture practices can increase the susceptibility of aquatic animals to pathogens due to environmental stress. Antibiotics are commonly used for disease prevention and control, but their frequent use in aquaculture can increase the risk of antibiotic‐resistant bacteria and resistance gene transmission, posing a threat to the health of aquatic animals and humans. Recent studies have shown that bacteriocins have inhibitory effects on different species of bacteria, fungi and viruses, and can even affect natural resistance structures such as bacterial biofilms, presenting promising prospects as antimicrobial agents. Bacteriocins have potential applications in various fields such as agriculture, food and medicine, but limited research has been conducted on their impact on aquaculture disease prevention and control, and the underlying mechanisms remain to be explored. Therefore, this review aims to summarise the classification, sources, preparation methods, antibacterial activity against multidrug‐resistant bacteria and application of bacteriocins as antimicrobial agents in aquaculture disease prevention and control. In addition, limitations of bacteriocin application in aquaculture and future research directions are also discussed.

Application of Organic Acid Salts as Feed Additives in Some Aquatic Organisms: Potassium Diformate

Antibiotics are the primary measures employed in the prevention and treatment of diseases in aquaculture. However, the frequent utilization of antibiotics can significantly impact the growth and reproduction of aquatic organisms, resulting in water pollution. The European Union (EU) has prohibited antibiotic additives in animal feed. Potassium diformate (KDF) represents the first non-antibiotic feed additive approved by the EU as a viable alternative to antibiotics. Its application in animal nutrition has been validated, demonstrating beneficial health effects. This article reviews the physicochemical properties, biological functions, synthesis conditions, and applications of KDF in aquaculture and looks toward to its future potential. It also provides insights into improving the utilization of KDF in aquaculture practices.

Distribution patterns and influential factors of pathogenic bacteria in freshwater aquaculture sediments.

Pathogenic bacteria, the major causative agents of aquaculture diseases, are a serious impediment to the aquaculture industry. However, the bioinformatics of pathogenic bacteria and virulence factors (VFs) in sediments, an important component of freshwater aquaculture ecosystems, are not well characterized. In this study, 20 sediment samples were collected from fish pond sediments (FPS), shrimp field sediments (SFS), fish pond sediment control (FPSC), and shrimp field sediment control (SFSC). Molecular biological information was obtained on a total of 173 pathogenic bacteria, 1093 virulence factors (VFs), and 8475 mobile genetic elements (MGEs) from these samples. The results indicated that (1) aquaculture patterns and sediment characteristics can affect the distribution of pathogenic bacteria. According to the results of the Kruskal-Wallis H test, except for Mycobacterium gilvum, there were significant differences (P < 0.05) among the four sediment types in the average abundance of major pathogenic bacteria (top 30 in abundance), and the average abundance of major pathogenic bacteria in the four sediment types followed the following pattern: FPS > SFS > FPSC > SFSC. (2) Pathogenic bacteria are able to implement a variety of complex pathogenic mechanisms such as adhesion, invasion, immune evasion, and metabolic regulation in the host because they carry a variety of VFs such as type IV pili, HSI-I, Alginate, Colibactin, and Capsule. According to the primary classification of the Virulence Factor Database (VFDB), the abundance of VFs in all four types of sediments showed the following pattern: offensive VFs > non-specific VFs > defensive VFs > regulation of virulence-related genes. (3) Total organic carbon (TOC), total phosphorus (TP), available phosphorus (AP), nitrite, and nitrate were mostly only weakly positively correlated with the major pathogenic bacteria and could promote the growth of pathogenic bacteria to some extent, whereas ammonia was significantly positively correlated with most of the major pathogenic bacteria and could play an important role in promoting the growth and reproduction of pathogenic bacteria. (4) Meanwhile, there was also a significant positive correlation between CAZyme genes and major pathogenic bacteria (0.62 ≤ R ≤ 0.89, P < 0.05). This suggests that these pathogenic bacteria could be the main carriers of CAZyme genes and, to some extent, gained a higher level of metabolic activity by degrading organic matter in the sediments to maintain their competitive advantage. (5) Worryingly, the results of correlation analyses indicated that MGEs in aquaculture sediments could play an important role in the spread of VFs (R = 0.82, P < 0.01), and in particular, plasmids (R = 0.75, P < 0.01) and integrative and conjugative elements (ICEs, R = 0.65, P < 0.05) could be these major vectors of VFs. The results of this study contribute to a comprehensive understanding of the health of freshwater aquaculture sediments and provide a scientific basis for aquaculture management and conservation.

The function of NLRP3 in anti-infection immunity and inflammasome assembly of common carp (Cyprinus carpio L.)

NLRP3 inflammasome can be activated by a variety of stimuli and plays an important role in protecting host from pathogen invasion and maintaining homeostasis. However, the activation mechanism of NLRP3 inflammasome in fish is still unclear. In the present study, the NLRP3 gene (CcNLRP3) was identified from common carp, which was 3069 bp in length and encoded a protein with five domains. Sequence analysis showed that NLRP3 was evolutionarily conserved, and CcNLRP3 was closely related to that in grass carp and zebrafish. Real-time PCR showed that CcNLRP3 was widely expressed in various immune-related tissues of healthy common carp, and significantly increased after stimulation with E. tarda, A. hydrophila and Cyprinus spring viremia virus (SVCV), suggesting that CcNLRP3 might be involved in the immune defense of common carp. The results of co-IP, spot formation, oligomerization and fluorescence localization showed that CcNLRP3 could interact with CcASC and assemble into inflammasome. The cytotoxicity assays showed that CcNLRP3 inflammasome was involved in the pyroptosis induced by CcGSDME. At the same time, CcNLRP3 could directly interact with CcCaspase-A/B and result in increased Caspase-B enzyme activity and LDH release, indicating that CcNLRP3 could also form inflammasome through ASC-independent pathway. Taken together, the results provide targets and theoretical basis for the prevention and control of infectious diseases in aquaculture.

Sargassum sp. extract improve hematological profile of tilapia fish (Oreochromis niloticus)

Background Strategies to increase body resistance and prevent disease in aquaculture include using vaccines, antibiotics, and probiotics. Today, the use of antibiotics with natural ingredients is becoming a trend. Sargassum sp is a natural ingredient that contains high antioxidants and antibiotics. Methods This research was conducted from March to May 2022 at the Biotechnology Laboratory, Faculty of Fisheries and Marine, Universitas Riau, in two stages: 1) the sensitivity of extracts of Sargassum sp. and 2) the application of Sargassum sp. extract orally in tilapia (O. niloticus). The parameters measured were clear zone, minimum inhibitory concentration, LD50 test of leaf extract of Sargassum sp. in tilapia (O. niloticus), hemoglobin levels, hematocrit, total leukocytes, total erythrocytes, leukocyte differentiation, and survival rate. Data on hematology parameters were tabulated and analyzed using a One-Way ANOVA followed by a Student Newman Keuls (SNK) test when deemed necessary. Results The results showed that the extract of Sargassum sp. inhibited the growth of Aeromonas hydrophila bacteria with a clear zone of 6.5-15.0 mm, which is classified as resistant. At doses of 2000, 2500, and 3000 ppm, it did not cause death in fish for 96 hours (LD50). Hematological parameters can be a sign of the health status of fish. Tilapia given Sargassum sp. in different doses gave an effect between treatments after 30 days of rearing and post-test against A. hydrophila bacteria (p&lt;0.05). The results showed that the hematology of fish fed with Sargassum sp. extract was in the normal or healthy range. Healthy tilapia had erythrocyte counts ranging from 1.34-2.11×106 cells/mm3, hematocrit 26.17-33.19%, hemoglobin 6.26-11.2 g/dL and total leukocytes 1.01-1.50×104 cells/mm3 and total erythrocytes 5.88-9.13×104 cells/ mm3. Conclusions A dose of 3000 ppm provided the highest health improvement against A. hydrophila bacterial infection.

Anthropogenic Vector Ecology and Management to Combat Disease Spread in Aquaculture.

Anthropogenic vectors (transfer mechanisms) can facilitate the introduction and spread of aquatic disease in marine farming regions. Preventing or interrupting pathogen transfers associated with movements of these vectors is key to ensuring productivity and profitability of aquaculture operations. However, practical methods to identify and manage vector risks are lacking. We developed a risk analysis framework to identify disease risks and management gaps associated with anthropogenic vector movements in New Zealand's main aquaculture sectors - Chinook salmon (Oncorhynchus tshawytscha), green-lipped mussels (Perna canaliculus), and Pacific oysters (Crassostrea gigas). Vectors within each sector were identified and assigned categorical risk scores for (i) movement characteristics (size, frequency, likelihood of return to sea), (ii) biological association with pathogens (entrainment potential, contribution to previous aquaculture disease outbreaks) and (iii) available best practice biosecurity methods and tools, to inform unmitigated and mitigated risk rankings. Thirty-one vectors were identified to operate within the national network and association with livestock was found to be a primary driver of vector risk rankings. Movements of live growing stock and culture substrates (e.g., mussel ropes) in shellfish farming had high-risk vector profiles that are logistically challenging to address, while vessel vectors were identified as the salmon farming sector's priority. The framework and rankings can be used to inform both research and management priorities in aquaculture and other primary production systems, including risk validation, vector roles in disease epidemiology, compliance with permit conditions, policy development, and treatment options.

Specific Phylotypes of Saprolegnia parasitica Associated with Atlantic Salmon Freshwater Aquaculture.

Saprolegniosis is a major destructive disease in freshwater aquaculture. The destructive economic impact of saprolegniosis on freshwater aquaculture necessitates further study on the range of Saprolegnia species within Atlantic salmon fish farms. This study undertook a thorough analysis of a total of 412 oomycete and fungal isolates that were successfully cultured and sequenced from 14 aquaculture sites in Scotland across a two-year sampling period. An ITS phylogenetic analysis of all isolates was performed according to whether they were isolated from fish or water samples and during enzootic or epizootic periods. Several genera of oomycetes were isolated from sampling sites, including Achlya, Leptolegnia, Phytophthora, and Pythium, but by far the most prevalent was Saprolegnia, accounting for 66% of all oomycetes isolated. An analysis of the ITS region of Saprolegnia parasitica showed five distinct phylotypes (S2-S6); S1 was not isolated from any site. Phylotype S2 was the most common and most widely distributed phylotype, being found at 12 of the 14 sampling sites. S2 was overwhelmingly sampled from fish (93.5%) and made up 91.1% of all S. parasitica phylotypes sampled during epizootics, as well as 67.2% of all Saprolegnia. This study indicates that a single phylotype may be responsible for Saprolegnia outbreaks in Atlantic salmon fish farms, and that water sampling and spore counts alone may be insufficient to predict Saprolegnia outbreaks in freshwater aquaculture.

Evaluation of a live attenuated vaccine against Edwardsiella piscicida by 16S rRNA sequencing

A complex and dynamic community of microorganisms is attached to the mucosal surface of the fish gut. Gut microbes play important roles in fish metabolism and immunity. Edwardsiella piscicida infection of turbot causes Edwardsiellosis, and vaccination is an effective method to prevent and control aquaculture diseases. Here, intraperitoneal vaccination by E. piscicida 10Δ, a live attenuated vaccine candidate, significantly upregulated the expression of immune response-related genes in the turbot spleen and enhanced the serum antibody titers of IgM. 16S rRNA amplicon sequencing revealed that the vaccination of E. piscicida 10Δ slightly reduced the relative abundance of intestinal microbiota in turbot. Meanwhile, E. piscicida 10Δ potentially conferred the intestinal microbiota metabolic capacity associated with carbohydrate metabolism, while hypothetically impaired their metabolic capacity related to fatty acid degradation and amino acid metabolism. Collectively, E. piscicida 10Δ can effectively stimulate the host immune responses and has no apparent influence on the relative abundance of intestinal microbiota, which can thus be considered as a potentially safe live attenuated vaccine.

Antiviral innovations in largemouth bass aquaculture: Unveiling the potential of arctigenin derivatives against Micropterus Salmoides rhabdovirus

Aquaculture confronts an escalating threat from viral infections, necessitating effective strategies to ensure fish health. This study investigated the comprehensive antiviral properties of compound A28 against Micropterus Salmoides Rhabdovirus (MSRV) in largemouth bass. Synthesized as a derivative of arctigenin, A28 was characterized for its inhibitory effects on MSRV at both cellular and organismal levels. To elucidate A28's impact on MSRV, cytotoxicity was gauged using the CCK-8 assay, revealing a safe concentration of 2.5 mg/L for A28 on GCO cell viability. At this concentration, A28 treatment resulted in remarkable inhibition rates, notably 99.14% for the MSRV nucleoprotein (N) gene and 99.46% for the glycoprotein (G) gene expression in GCO cells. Additionally, RT-qPCR analysis demonstrated a dose-dependent inhibition of MSRV genes (N and G) with increasing A28 concentrations. Morphological assessment revealed a reduction in MSRV-induced cytopathic effects in the presence of 2.5 mg/L A28 after 48 h. Intriguingly, preventive and therapeutic experiments underscored A28's dual role against MSRV infection. Water stability assessment indicated a sustained inhibitory effect of A28 on MSRV for approximately 2 days. Notably, A28 demonstrated the capacity to alleviate MSRV-induced nuclear and mitochondrial damage, underscoring its cytoprotective effects. In vivo experiments on largemouth bass revealed that A28 significantly enhanced fish survival rates upon MSRV challenge, with a notable 38% increase following A28 treatment. Concurrently, A28 upregulated fish immune-related genes, furnishing molecular evidence of its immunomodulatory effects. Furthermore, A28 exhibited efficacy in suppressing the horizontal transmission of MSRV in fish, suggesting its potential as a therapeutic agent in aquaculture settings. In conclusion, compound A28 emerges as a promising antiviral agent against MSRV in largemouth bass, offering insights into its potential application in managing aquaculture diseases. The findings provide a foundation for further research on A28's pharmacokinetics, environmental impact, and scalability for practical aquaculture applications.

Infectious characteristics of some Vibrio spp. phages isolated in shrimp farming of the Mekong delta

Vibrio spp. Were a cause of serious disease in aquaculture. This study aimed to develop a Vibrio spp. inhibition method that is safe and friendly for the environment, namely bacteriophage (phage). Vibrio spp. and their phages were isolated from shrimp, water, and mud from farms in Mekong Delta provinces (Kien Giang, Soc Trang, and Bac Lieu provinces). Then, the phage influence on the bacterial concentration and the toxR gene was investigated by comparing the gene sequences pre- and post-infection. The polymerase chain reaction identified 31 strains of Vibrio spp., including 9 of Vibrio parahaemolyticus. Then, using several isolated Vibrio spp. as hosts, 32 phage strains were isolated. Results found that each bacteriophage affected the Vibrio toxR gene in specific ways. Phage ST9 and phage ST10 did not change bacterial concentration, but they could change nucleotides at 4 positions compared to the V. parahaemolyticus sequence. Nevertheless, phage KG6 could reduce bacterial concentration but did not affect gene sequences. The bacteriophages can affect bacteria through several mechanisms, including reducing the bacterial concentration via the lytic process or affecting genes encoding bacterial virulence. These findings open a new direction in phage therapy research if such an effect can reduce or neutralize bacterial virulence.

Chitosan nanogel aqueous treatment improved blood biochemicals, antioxidant capacity, immune response, immune-related gene expression and infection resistance of Nile tilapia.

Candida albicans is a pathogenic yeast recently associated with diverse diseases in aquaculture. The present study investigated the efficacy of chitosan nanogel (CNG) in ameliorating effects of C. albicans on Nile tilapia (Oreochromis niloticus). Fish were randomly distributed into four groups (control, waterborne CNG at 75μg/L, intraperitoneally challenged with C. albicans (1.8×107CFU/mL), and waterborne CNG at 75μg/L+C. albicans at 1.8×107CFU/mL). Results showed that C. albicans infection reduced survival rate (57.5%) and caused marked clinical symptoms in fish among all infected groups. Substantial declines in immunological (complement 3, lysozyme, and immunoglobulin M), protein (total protein and non-albumin protein), and antioxidant (catalase, glutathione peroxidase, and superoxide dismutase) biochemical endpoints were exhibited, The C. albicans infected group also showed marked down-regulation in the expression of immune-related genes, including toll-like receptor 2 (TLR-2), transforming growth factor beta2, tumor necrosis factor alpha, interleukins (IL-1β, IL-6, and IL-10), and antiapoptotic gene (B-cell lymphoma, BCL-2). The expression of the apoptotic gene (Bcl-2 associated X protein, BAX) was up-regulated in fish challenged by C. albicans. The application of waterborne CNG to fish challenged with C. albicans infection improved fish survival (79.5%) and all other measured parameters. The main finding of this work was that CNG is a nanotechnology with potential for preventing degraded health status by C. albicans infection in tilapia, and thus has promise as an intervention in aquaculture settings.

Potential biocontrol for bacterial and viral disease treatment in aquaculture: a minireview.

Aquaculture is part of the crucial industry that supplies food, especially for the global human population that is gradually increasing annually. Innovations of culture techniques have been improved throughout the years but aquaculture is regularly susceptible to bacterial and viral diseases. Numerous factors could contribute to occurrence of disease and usually they are from environmental or human stressors on the cultured animals. Synthetic chemicals in commercial treatments may yield fast results however, the side effects are usually unknown until it has taken effect. Therefore, biological control methods to treat diseases in aquaculture are preferred. This mini review provides an overview of different potential biocontrol practices for treatment of bacterial and viral diseases. Bacteriophage causes death of pathogenic bacteria by killing the cell and continue to multiply until all targeted pathogenic bacteria are eliminated. Probiotic, prebiotic, synbiotic, biofloc, and immunostimulants are beneficial products from the respective organisms that are effective in inhibiting pathogens. Vaccines introduce inactivated pathogen into the body to stimulate the immune system, while genetic modifications involve alteration and selection of disease resistant genetics.

Genetic parameters for host-response to acanthocephaliasis caused by the endoparasite Neoechinorhynchus buttnerae in the Amazon fish Colossoma macropomum

Tambaqui (Colossoma macropomum) is the main native fish produced by Amazon aquaculture. However, the production chain of this fish has been significantly affected by acanthocephaliasis, caused by the endoparasite Neoechinorhynchus buttnerae. The selection of superior genotypes for resistance and resilience to acanthocephaliasis is a fundamental approach to improve production in the context of environmental sustainability and food security. Thus, the objectives of this study were to 1) conduct an experimental challenge against the endoparasite N. buttnerae in tambaqui, and 2) determine the genetic parameters of disease traits caused by N. buttnerae in an experimental breeding population of tambaqui. Estimation of genetic parameters was performed using a genomic relationship matrix (SNPs data) obtained from an experimental challenge performed in 70 full-sib families. The experimental challenge was successfully performed in three replicate tanks, using the parasite eggs in the ichthyoplankton as source for a natural route of infection, which in turn was induced through oral filtration the plankton. The total gain in body weight of all individuals was measured during the infestation period, as a measure of Resilience (RSF) and averaged 42 g (SD = 21.8). The average parasite abundance per animal at the end of the challenge period, indicating Resistance (RTCT), was about 205.2 parasites (SD = 178.6). The heritability estimates for these traits ranged from 0.17 ± 0.04 to 0.20 ± 0.04, indicating the presence of low to moderate heritability levels for host response against N. buttnerae in tambaqui. Genetic correlations between resistance and resilience traits were consistently negative (favorable) and statistically significant, ranging from −0.512 ± 0.134 to −0.252 ± 0.166. These results suggest the possibility of selecting animals for both resistance and resilience simultaneously. The significant genetic variation found for N. buttnerae resistance and favorable genetic correlations with resilience in tambaqui indicated that selecting superior genotypes is a viable approach to reduce the impact of acanthocephaliasis disease in aquaculture.

The Influence of Betel Leaf Extract Administration in Enhancing Non-Specific Immunity to Combat Diseases in the Aquaculture Sector (Review)

This review aims to investigate the impact of betel leaf extract administration in enhancing non-specific immunity in fish within the context of aquaculture. A literature review was conducted to evaluate previous studies, analyze the mechanisms of action of active compounds, and provide practical recommendations for field implementation. The review results indicate that betel leaf extract has antimicrobial potential that can inhibit the growth of bacteria, viruses, and parasitic agents causing diseases in cultured fish. The administration of this extract also stimulates non-specific immune responses, including increased production of immune cells such as macrophages and lymphocytes. The antioxidant effects of compounds in betel leaves provide protection against oxidative stress, enhancing fish resilience to unfavorable environmental conditions. Despite these positive findings, further research is needed to deeply understand the mechanisms of action of active compounds, taking into account environmental factors in betel leaf extract administration. Integration with other disease management strategies and strict monitoring of environmental safety are crucial aspects of practical implementation. In conclusion, the administration of betel leaf extract can be a promising alternative to enhance fish resistance to diseases in aquaculture. Administering betel leaf extract in feed and water can improve survival rates and egg hatching. Collaboration among researchers, farmers, and other stakeholders is necessary to optimize the practical application of these findings, with the goal of enhancing productivity and sustainability in the aquaculture sector as a whole.Top of Form

Analysis of alternative splicing provides insights into its vital roles in immune responses of half-smooth tongue sole (Cynoglossus semilaevis) against Vibrio anguillarum

Aquaculture plays important roles in global food security. Prized as a valuable commercial species, the aquaculture industry of half-smooth tongue sole (Cynoglossus semilaevis) has faced unprecedented challenge due to bacterial diseases, including vibriosis caused by Vibrio anguillarum. Alternative splicing (AS) is an important layer of post-transcriptional regulation, being involved in almost all biological processes, including development, reproduction, and immunity. However, its roles in immunity in half-smooth tongue sole remain elusive. In this study, therefore, we profiled the changes of alternative splicing in half-smooth tongue sole after infection with different concentrations of V. anguillarum, and investigated their functions by both enrichment analysis and targeted gene transcript overexpression analysis with half-smooth tongue sole macrophages. Intriguingly, differentially alternatively spliced (DAS) genes were found to be involved in RNA splicing for each bacterial treatment and for the shared gene set, consistent with previous studies that splicing factor themselves often underwent alternative splicing. A set of 12 immune-related shared DAS genes were identified, including hp, c5, and traf2b. Targeted gene analysis using the shared DAS gene, haptoglobin (hp), showed that alternative splicing resulted in changes of protein domains, and overexpression analysis demonstrated that two transcripts of hp exhibited contrary roles in stimulating or reducing the expression of immune factors in response to lipopolysaccharides (LPS), reflecting the vital roles of alternative splicing in immunity of tongue sole. DAS events were further verified by qRT-PCR (20 primer pairs for 10 DAS events) to confirm the reliability of our bioinformatics analysis. This study, for the first time, revealed the involvement of alternative splicing in immune responses of half-smooth tongue sole using both omics data and targeted gene functional analysis, setting a solid foundation for further analysis and providing clues for potential usage in controlling bacterial diseases in aquaculture.

Unlocking Eco-solutions: Analyzing parasitic disease resistance in Yellow River carp (Cyprinus carpio haematopterus) under different ecological treatments

Combatting parasitic diseases in intensive aquaculture is crucial for sustainable and healthy fish production. The use of chemical pesticides, although effective, poses environmental and public health risks. To address this issue, we investigated the impact of ecological treatments on the occurrence of parasitic diseases in intensive culture of Yellow River carp (Cyprinus carpio haematopterus) pond. A comprehensive survey was conducted in 160 ponds, and the data were collected through a normative questionnaire which included the main factors related to ecological management such as pond water sources and depth, stocking methods, whether or not mixed culture with carps, water quality adjustment and sediment operation methods. Whether parasitic diseases have happened was determined by combination of both field investigation and laboratory diagnostic methods. For assessment the relationship between ecological treatments and parasitosis occurrence, the data were analyzed using two methods, including univariate and multivariate logistic regressions. The final model revealed the influence of five significant ecological treatments (P < 0.05) on parasitosis occurrence in the ponds. The three ecological treatments significantly reduced disease occurrence, which were mixed culture with silver and/or bighead carp, maintaining water quality at intervals of ≤7 days, and aeration time > 10 h in 24 h. Additionally, utilizing underground water, avoiding sediment stirring increased the incidence of the parasitosis. These findings demonstrate the effectiveness of appropriate ecological treatments in minimizing parasitic diseases in Yellow River carp, supporting sustainable aquaculture development.

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.