This review aims to summarize the current knowledge regarding the effects of various dietary additives on osmoregulation in aquaculture. It covers salt supplements, potassium supplements, myo-inositol supplements, metal ion supplements, and monosaccharides, emphasizing their importance in improving osmotic adjustment. The review provides an overview of the underlying mechanisms involved in osmoregulation and highlights the role of some specific dietary additives in promoting osmotic balance. Dietary salt and inorganic potassium directly provide ions for osmotic balance, while dietary metals, inositol, and monosaccharides can help mitigate the effects of osmotic stress and enhance the body's capacity for osmoregulation. Additionally, the addition of exogenous glucose not only provides energy required for osmoregulation but also acts as an osmolyte itself, contributing to osmoregulation. The review underscores the need for further research to better understand the interactions between dietary additives and osmoregulation in aquaculture. It also highlights the importance of considering species-specific requirements, optimal dosage levels, and the potential synergistic effects of combining multiple additives. Overall, carefully selected and properly administered dietary additives have the potential to improve osmoregulatory capacity, mitigate osmotic stress, and enhance the overall performance and welfare of cultured aquatic organisms. Future research should focus on elucidating the underlying mechanisms and optimizing the application of dietary additives to maximize their effectiveness in aquaculture systems.

Streptococcosis is one of the septicaemic bacterial diseases of public health concern due to its zoonotic potential. Its luxurious existence in wild marine fish from an open water body strongly suggests presence of massive sewage pollution. The aim of the current study was to identify and characterize most common streptococci affecting common pandora (Pagellus erythrinus) inhabiting the Mediterranean coast of Tripoli. A total number of 270 common pandora were clinically examined for possible streptococcal infection and non-streptococcal infection. The fishes were collected from the area extending from Tripoli to Tajoura (east to Tripoli) during the three seasons, summer, autumn, and spring. No fish samples were available during winter due to the bad climate / storms along the entire western Libyan Mediterranean coasts. Streptococcus iniae, Streptococcus dysgalactiae, Streptococcus phocae, Enterococcus faecalis, and other non-streptococcal species, such as Aeromonas hydrophila, Pseudomonas anguilliseptica, and Photobacterium damselae sub species damselae were biochemically identified. Regardless of the season, S. iniae and E. faecalis were the most prevalent streptococcal species (13% and 8.88%, respectively). In contrast, the most retrieved non-streptococcal species were A. hydrophila, followed by Pseudomonas anguilliseptica, with a prevalence of 10%, and 14.44%, respectively. The highest infections were recorded during autumn, followed by summer, then spring with percentages of 53.34%, 50%, and 43.4%, respectively. The majority of the isolates were sensitive to erythromycin, florfenicol, and sulfamethoxazole-trimethoprim. The molecular screening using the sequences of 16S rRNA genes has confirmed the phylogenetic relationship to S. dysgalactiae, E. faecalis, S. iniae, and S. phocae isolates with similarity percentages exceeding 99.6%. The sequences were deposited in the GenBank with accession numbers (OK033868, OK033869, OK033870, and OK033871). To sum up, the obtained results highly suggests that the common pandora fish from Tripoli coast of the Mediterranean is biologically contaminated with various zoonotic streptococci which could be considered as a biological indicator for municipal sewage pollution.

The yellow catfish is an economically significant freshwater fish with increasing importance in aquaculture. However, the low temperature environments prevalent in certain regions pose challenges to its growth, development, and overall health. This study aimed to explore the impact of dietary arginine (Arg) addition on the growth, digestive capacity, and intestinal antioxidant response in fish under low temperature acclimation (18 °C). Total 720 fish were randomly distributed into six groups, each containing 120 fish. Over the course of eight weeks, each group was fed with diets about varying Arg concentrations (1.79–3.26 g/kg). The results indicated that Arg supplementation resulted in an increase in specific growth rate (SGR), feed intake (FI), feed efficiency (FE), as well as pancreatic enzyme activities in both pancreas and intestine. Conversely, malondialdehyde (MDA) and protein carbonyl (PC) contents initially decreased but increased with higher Arg concentrations. Glutathione peroxidase 1a (GPX1a) showed a positive correlation with nuclear factor-erythroid 2-related factor-2 (Nrf2), showing its role in antioxidative capacity. Furthermore, this study revealed that Arg significantly enhanced the activities of anti-superoxide anion, anti-hydroxyl radical, and anti-oxidative enzymes, along with the relative mRNA abundance of Copper-Zinc superoxide dismutase (CuZnSOD), catalase, GPX1a, glutamate-cysteine ligase catalytic subunit (GCLC), and Nrf2 in the intestine. It was determined that yellow catfish weighing between 61.0 g and 89.0 g require an intake of 26.8 g of Arg per kilogram of diet based on polynomial regression analysis of specific growth rate (SGR), which is equivalent to 37.0 g of dietary protein, under sub-low temperature conditions of 18 °C.

Neonicotinoid insecticides specifically target insect subtypes of nicotinic acetylcholine receptors. Acetamiprid (ACE: C10H11ClN4), the neonicotinoid insecticide, is used to control crop insect pests worldwide. It is a nitrile, monochloropyridine, and carboxamidine that is highly soluble and accessible to waterways. There, it causes neurotoxic and oxidative perturbance to non-target organisms. The unionid mussel Chamabradia rubens is a common Northern River Nile suspension feeder. The current study aimed to assess ACE filtration from waters by C. rubens, and whether this biological power can reduce ACE effects on fish. Removal of ACE by C. rubens was assessed using LC-MS/MS. Zebrafish Danio rerio adults were exposed to different sublethal doses of ACE in the presence or absence of C. rubens in their aquaria. The results showed that mussels could remove significant ACE amounts from water, where it accumulated mostly in the digestive gland. The presence of C.rubens in zebrafish aquaria having ACE was accompanied by significant upregulation of antioxidant enzyme gene transcripts and total H2O2 scavenging, in contrast to mussel-free ACE-exposed groups. Meanwhile, liver triglycerides rose 5-6-fold in response to ACE in the “Fish-Only” groups, indicating an ACE-induced hepatotoxicity. Also, Insulin-like growth factor 1 (igf1) and fish body mass increased more in “Fish+Mussel” groups than in the “Fish-Only” ones. In aggregate, these findings suggest that the Nile mussel could reduce the oxidative stress and metabolic changes induced in fish by ACE. This can contribute valuable environmental and economic benefits upon the use of this mussel as a biofilter.

THE virulent clonal populations of Aeromonas spp. are recognized as the etiological agent of motile Aeromonas septicemia (MAS) outbreaks in aquaculture. This study aimed to identify Aeromonas spp. isolated from diseased Oreochromis niloticus , evaluate their virulence factors, and assess their resistance to antimicrobial agents. Species identification was conducted through analysis of the gyrB genes. Antibiotic resistance phenotypes and genotypes (blaTEM , blaCTX-M , aac(61)-Ib-cr , and intI1) were determined. The results indicated that 44,4% of the isolates belonged to A. veronii , 38.9% to A. sobria , and 16.7% to A. hydrophila. PCR analysis revealed the presence of blaTEM , aac(61)-Ib-cr , and intI1 genes among 100%, 77.8%, and 83.3% of the isolates, respectively, while blaCTX-M was not detected. In conclusion, the detection of the aac(6')-Ibcr gene in aquatic environments can serve as a significant indicator of multi-drug resistance (MDR). The presence of MDR, particularly mediated by integrons in Aeromonas , raises serious concerns regarding potential health risks. Moreover, the emergence of MDR complicates the efficacy of therapeutic treatments for infections. Therefore, adopting a comprehensive One Health approach becomes imperative to effectively control the spread of MDR and mitigate its impact on public health.

AbstractIn recent decades, probiotics have become an acceptable aquaculture strategy for shrimp growth promotion and immune modulation. This study aimed to evaluate the effect of Bacillus velezensis on Litopenaeus vannamei following a 60-day trial. L. vannamei (3 ± 0.4 g) were distributed into four groups with three replicates per group and fed an isonitrogenous diet supplemented with B. velezensis at 0, 1 × 107, 1 × 108, and 1 × 109 CFU/g, which were defined as the control, G1, G2, and G3 groups, respectively. B. velezensis significantly improved the growth, survival rate, and proximate body composition of L. vannamei (P < 0.05). All groups fed the B. velezensis diet showed significant increases in digestive enzymes (lipase, amylase, and protease), superoxide dismutase (SOD; G3), catalase (CAT; G3, G2, and G1), lysozyme activity (G3 and G2), immunoglobulin M (IgM), bactericidal activity BA%, alkaline phosphatase (AKP), and acid phosphatase (ACP) compared with the control group (P < 0.05). Malondialdehyde (MDA), triglycerides, cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels were significantly decreased in all groups fed B. velezensis diet compared with the control group (P < 0.05). The expression levels of SOD (G3), LZM, and serine proteinase genes were significantly higher in L. vannamei fed diets containing B. velezensis than in the control group (P < 0.05). This is the first study to address the effects of B. velezensis on the expression of the LZM and serine proteinase genes in L. vannamei. L. vannamei fed diet containing B. velezensis had more B and R cells in its hepatopancreas than did the control group. In conclusion, B. velezensis is a promising probiotic that can be safely added to the diet of L. vannamei with 1 × 109 CFU/g. Its application had a positive influence on the health status, survival rate, nutritional value, and immunity of L. vannamei.

This study was conducted to determine the effect of replacing fishmeal (FM) with fermented soybean meal (FSBM) for 12 weeks on the growth performance, feed utilization, immunological parameters, antioxidant enzyme assays and lipid peroxidation, digestive enzymes, and histopathological analysis of juvenile Litopenaeus vannamei ( L. vannamei ). By substituting 0.0%, 20%, 30%, and 40% FSBM for fishmeal (w/w), four isonitrogenous diets were generated. A total of 300 juvenile L. vannamei (1.59 ± 0.01 g) were randomly allocated to the experimental fiber tanks at a rate of fifteen shrimp per tank, with three replicates for each treatment. Growth performance and feed utilization decline considerably ( P < 0.05) with increasing amounts of FM replacement with FSBM in diets. In comparison to the juveniles fed the other experimental diets, the diet containing a moderate level of FM replacement (20% FSBM) considerably enhanced growth performance and feed consumption during the feeding trial. The 20% FSBM-fed group had the highest protein content. In contrast, raising FSBM levels significantly increased lipid content ( P < 0.05) compared to the control. However, there were no statistically significant differences ( P > 0.05) across FSBM treatments. Hemolymph plasma total protein (TP) concentration and lysozyme activity were substantially greater ( P < 0.05) in 20% FSBM compared to 40% FSBM ( P < 0.05). In addition, 20% FSBM exhibits a substantial ( P < 0.05) increase in the activity of antioxidant enzymes (CAT SOD, GPX, and GR). In contrast, the control and 30% FSBM groups had considerably more lipid peroxidation markers (MDA) than the 20% and 40% FSBM groups. Hepatopancreas amylase activity was considerably elevated ( P < 0.05) in the control group and with 40% FSBM. In addition, hepatopancreas and intestinal protease and lipase activity increased significantly by 20% FSBM. Considerably, more B cells were present in the 40% FSBM diet than in the control diet; however, they were significantly less prevalent in the 20% and 30% FSBM diets ( P < 0.05).

The probiotics are being used as ecofriendly and bioremediation tools for developing sustainability to aquaculture. The present study was conducted to explore the practical capability of using dietary lactic acid bacteria (Pediococcus acidilactici) probiotics and see how its dose variation affected the water quality, growth performance, survival rate, body composition, blood biochemical parameters, and intestinal histology of European sea bass (Dicentrarchus labrax L.). A total of 120 fingerlings with an initial weight of 9 ± 0.2 g were divided into four groups, each with three replicates. The feeding experiment lasted for 60 days. In addition to the control (without probiotics) (T0), fish were fed diets containing (T1) 2.0, (T2) 2.5, and (T3) 3.0 g of probiotics per kg of diet twice a day. When compared to the control, sea bass fed probiotic-supplemented diets had significantly higher growth parameters, fish body “crude lipid,” and villi height ( p < 0.05 , p < 0.01 , and p < 0.001 ). The P. acidilactici probiotic treatments improved survival rate, feed conversion ratio, body composition, and blood biochemical markers, but not statistically significant ( p > 0.05 ). Also, in regard to water quality, P. acidilactici drastically reduced ammonia and pH levels. In this experiment, fish fed with a dosage of 3.0 g of this commercial probiotic per kg of probiotics performed better. The study found that including probiotics in the diets of European sea bass improved growth, body composition, survival rate, blood biochemical markers, intestinal histology, and some water quality parameters.

Cyclophosphamide, a common chemotherapeutic and immune suppressor agent, is regularly used in research to weaken the immune system in laboratory animal models. Nile tilapia (Oreochromis niloticus) is a widely used experimental fish model for immune-modulatory research; with the lack of knowledge about the immune-compromised tilapia model, an urgent need is to develop and optimise such a model. Sixty healthy Oreochromis niloticus fish, average weight 50 ± 10 g, were divided into four experimental groups. Fish in group I, negative control group, were injected with phosphate-buffered saline only, and fish in groups II, III and IV were injected with cyclophosphamide (CP) at 100, 200 and 400 mg/kg body weight (BW), respectively, via the intraperitoneal route. Different immune-related parameters were investigated 3 weeks after CP injection. The results have revealed a significant decrease in total red blood cells (RBCs), white blood cells (WBCs) and thrombocyte counts and reduced haemoglobin and haematocrit values in CP-treated fish, especially those injected with 200 mg/kg BW compared with the control group (p < 0.05). Also, significantly lower levels of serum proteins (total protein, albumin, α1- and γ-globulins) were observed in CP-treated fish, especially those injected with 200 mg/kg BW in comparison with the control group (p < 0.05). Furthermore, CP-treated fish showed a reduction in the expression of immune-related genes (interleukin-1, and tumour necrosis factor-α in spleen and tumour necrosis factor-α and transforming growth factor β-1 in head-kidney), especially those injected with 200 mg/kg BW compared with the control group (p < 0.05). In conclusion, the Oreochromis niloticus immune-suppressed model can be induced by intraperitoneal CP injection at 200 mg/kg BW.

The present study evaluated the effects of dietary onion (Allium cepa)powder and its extracts on growth, blood biochemical parameters, non-specific immune parameters and potential disease resistance against pathogenic Aeromonas hydrophila infection in Oreochromis niloticus. Fish formulated diets containing onion powder (1% or 0.5%) or onion alcoholic extracts (1% or 0.5%). At the end of the experiment, the weight gain and specific growth rate were significantly increased than control. Besides, red blood cells (RBCs) and haemoglobin (Hb) showed a significant increase with insignificant changes of leukocytic cells count (WBCs), triglycerides, creatinine and uric acid levels. Results showed significant increase of total protein and albumin, and significant enhancement of innate immune response including serum globulins, serum antiprotease, lysozyme activities, myeloperoxidase content and the phagocytic index compared with the control group. Meanwhile feeding on onion increased superoxide dismutase, catalase activities and glutathione-S-transferase but significantly decreased hepatic peroxidase. The cumulative mortality of O. niloticus injected with A. hydrophila exhibited relatively low mortality levels in all onion supplemented groups. The relative per cent survivals were 100%, 100%, 80% and 70% in 1% onion powder, 0.5% powder, 1% extract and 0.5% extract groups, respectively, compared with control (60%). Additionally, there was a significant increase in relative immune gene expressions of interleukin 1-beta (IL-1 beta), and transforming growth factor-beta 1 (TGF-beta 1) in head kidney tissues of treated groups than the control. These results confirm the anti-inflammatory and antioxidative activities of dietary onion with its beneficial effects on growth performance and disease resistance against A. hydrophila in O. niloticus.

VIBRIO anguillarum causes severe economic losses in fish and shellfish species and poses public health concerns. This study aimed to provide some information about the prevalence and virulence determinants of V. anguillarum isolated from the farmed Oreochromisniloticus fish fingerlings nearby Qarun Lake, El-Fayoum Governorate, Egypt. PCRtargeting the rpoA (RNA polymerase alpha subunit) gene was done forconfirmation of Vibriospp. Moreover, V. anguillarum isolates were biochemically identified and confirmed by 16S rRNA gene sequence. V. anguillarum isolates produced caseinase, gelatinase, lipase, lecithinase, haemolysins, and possessed biofilm formation. The virulence-related genes; empA, vah1, vah3 and vah4, flaA, angM, and angR were detected in all tested isolates. Therefore, proper identification of V. anguillarumis crucial to better understand the ecology and distribution patterns of such pathogen within Egyptian aquaculture. Moreover, the water quality in these farms near Qarun Lake was less supportive for larval rearing activities of O. niloticus fish.

The current study was designed to investigate the potential of bioorgano (thymol and carvacrol) with and without the water quality improvement product Q Z Toss™ on growth and health performance of Nile tilapia (Oreochromis niloticus). Six fish groups were maintained on control diet supplemented with the bioorgano for one month. Both bioorgano dietary levels exhibited significant increase in growth parameters as well as in white blood cell count with no negative impacts on both hepatic and renal functions. The histopathological examination revealed better intestinal epithelial status in bioorgano treated groups than other groups, and an increase in intestinal villi length regardless of bioorgano concentration used. while the posterior kidney showed activation of melanomacrophages centers (MMCs) which is linked to enhancement of fish immune response. Therefore, we can recommend the dietary inclusion of bioorgano in aqua-feed along with Q Z Toss™ application in rearing water as an efficient method to achieve feasible and sustainable fish production.

In recent decades, several mass mortalities were recorded in riverine ayu (Plecoglossus altivelis) in Tokyo Metropolis, Hiroshima Prefecture, and Yamaguchi Prefecture, Japan; in these outbreaks, microbiological and pathological examinations revealedEdwardsiella ictalurias the causative agent. In this study, histopathological findings and immunohistochemical localization of the bacteria following experimental infection of ayu were discussed. Infection experiments were performed using 44 healthy cultured ayu fingerlings usingE. ictaluriisolate (H90). The fish were injected with the isolate intraperitoneally with a dose of 5.1 x 10(5)cfu/fish, while the control fish were injected with sterile phosphate buffered saline. The fish were observed for clinical signs, with daily collection of dead fish, and isolation of bacteria from the posterior kidney was performed and confirmed to beE. ictaluriby slide agglutination using anti-PH0744 serum. Daily collection of five moribund fish for necropsy and tissue specimens collection from hepatopancreas, spleen, posterior kidney, gills, brain, heart, and intestine for histopathological and immunohistochemical examination. Post-mortem lesions were recorded as exophthalmia, bloody ascitis, hemorrhagic kidney and distended gallbladder, meningio-encephalitis, hemorrhagic vent, and petechial hemorrhages on viscera. Histopathological examination revealed diffuse severe congestion in blood vessels and several degenerative and necrotic changes inconcurrent with positive antigenic staining by immunohistochemistry.

The antimicrobial activity of tilapia piscidin 3 (TP3) was determined in vitro against a locally isolated Aeromonas hydrophila. A 388 bp fragment was amplified from the TP3 cDNA and sequenced. The coding sequence (CDS) of TP3 was estimated to be 231 bp codes for 76 amino acids long and stop codon. In silico analysis was performed to detect both the signal peptide and the prodomain cleavage sites to follow the amino acids number 22 and 70, respectively. Based on this, a peptide 23 amino acids long with a remarkably high computed antimicrobial probability was synthesized and used in the subsequent experiments. The antimicrobial activity of TP3 was determined with minimum inhibitory concentration (MIC) and minim um bactericidal concentration (MBC) methods. TP3 exhibited relatively weak antimicrobial activities against the tested bacteria. A challenge experiment was then performed in Nile tilapia with low and high doses of A. hydrophila, followed by timely recognition; after 3, 6, 24 h, and 7 days of the specific TP3 gene expression, immunohistochemical localization was also performed. Histopathological examination revealed provoked inflammatory responses and congestion in the same organs of TP3 expression. Immunohistochemical localization showed that A. hydrophila induced tilapia fish to express TP3 after 24 h within the gills, intestine, hepatopancreas, spleen, and posterior kidney. In quantitative real time (RT)-polymerase chain reaction analysis, the high dose showed higher mRNA expression levels than the low dose, and its expression levels increased in the A. hydrophila-infected fish. It was therefore concluded that TP3 plays an essential role in fish immunity.

The antimicrobial activity of tilapia piscidin 4 (TP4) was determined in vitro against four bacterial strains, Aeromonas hydrophilla, Pseudomonas fluorescens, Streptococcus iniae and Vibrio anguillarum. Nile tilapia were infected with low and high doses of the tested pathogens; after 3, 6, 24 h and 7 days of the specific TP4 gene expression, tissue immunolocalization was also performed. Histopathological examination revealed septicaemia and necrosis of hemopoietic tissue for all of the tested bacteria. Immunolocalization showed abundance in S. iniae-infected fish tissues. Quantitative RT-PCR analysis revealed that high doses raised mRNA expression levels compared to low doses and expression levels increased in the infected fish, particularly after 24 h, indicating that TP4 exerts potent bactericidal activity against some fish pathogens and plays an essential role in fish immunity.

The practical difficulty of parenteral application of fish vaccines against devastating fish diseases diverted the interest toward oral vaccination. Search for effective methods to enhance the oral uptake of viral and bacterial vaccines is continuing. The current research focus on a new role of mucosal fish vaccine adjuvants inducing the antigen uptake by enhancing vascularity or increasing intestinal permeability. Some inflammatory substances cause reversible pathology to the intestinal epithelium, which could be employed for the transepithelial passage of vaccine particles. The natural inflammatory substances used were capsaicin, piperine, and okadaic acid as 1 mg, 2 mg, and 1 μg/fish, respectively. Two inactivated vaccines were used as antigens to test the effect of these inflammatory substances in two different fish hosts. Tested vaccines were inactivated redspotted grouper nervous necrosis virus vaccine in sevenband grouper (Epinephelus septemfasciatus) and inactivated Edwardsiella tarda vaccine in red sea bream (Pagrus major) fish models. The inflammatory substances and each vaccine were anally intubated to fish. Capsaicin proved to be effectively aiding the transepithelial passage of vaccine particles more than piperine, while okadaic acid had no detectable effect.

The current study was designed to investigate the probiotic potential of the BiogenO with and without the water quality improvement product (Q Z Toss™) on growth and health performance of Nile tilapia (Oreochromis niloticus). Four fish groups were maintained on control diet supplemented with the BiogenO for one month with or without inclusion of Q Z Toss™ in water. Dietary levels of BiogenO exhibited significant raise in growth parameters with no harmful impacts on hepatic functions. Importantly, Q Z Toss™ supplemented group showed obvious decline of water ammonia level. However, water ammonia level didn’t change in BiogenO treated fish compared to control. The histopathological examination revealed better hepatopancreas and intestinal epithelial status in BiogenO treated groups than other groups. Therefore, we can recommend the dietary addition of BiogenO in aqua-feed along with Q Z Toss™ application in rearing water as a proficient method to achieve feasible and sustainable fish health.