The present study aimed to evaluate the effect of dietary fermented extracts sourced from Saccharomyces cerevisiae (nucleotides, β-glucans and MOS) (Hilyses^®) on the production and health of Nile tilapia (Oreochromis niloticus) broodstock, as well as on seed survival and performance. The trial was performed in a hatchery along the spawning season and continued in the laboratory to monitor the performance in fry and fingerlings. The broodstock were divided into two groups, (C) fed a basal diet and (H) fed 0.4% Hilyses. Blood and histological parameters, antioxidant power, cortisol level and the expression of some immune-related (TLR-2, IL-1β and TNF-α) and growth-related genes (MUC-2 and IGF-1) were measured. The obtained seeds were subdivided into four treatments: (C-C) fed a basal diet, (C-H) fed 0.4% Hilyses, (H-C) fed a basal diet and (H-H) fed 0.4% Hilyses. Results revealed that the dietary inclusion of Hilyses in the broodstock increased seed production, survival, hematological parameters, and antioxidant power. Moreover, it improved the intestinal microstructure and upregulated the immune- and growth-related genes. The growth indices of fry and fingerlings were significantly increased in all Hilyses-treated groups (p < 0.05). The performance in the (H-H) group significantly surpassed those of all groups. Therefore, dietary fermented yeast could be used as a strategic solution to sustain tilapia production.

Background: In recent years, anthropogenic activities have released heavy metals and polluted the aquatic environment. This study investigated the ability of the silica-stabilized magnetite (Si-M) nanocomposite materials to dispose of lead nitrate (Pb(NO₃)₂) toxicity in Nile tilapia and African catfish.Results: Preliminary toxicity tests were conducted and determined the median lethal concentration (LC₅₀) of lead nitrate (Pb(NO₃)₂) to Nile tilapia and African catfish to be 5 mg/l. The sublethal concentration, equivalent to 1/20 of the 96-hour LC₅₀Pb(NO₃)₂, was selected for our experiment. Fish of each species were divided into four duplicated groups. The first group served as the control negative group, while the second group (Pb group) was exposed to 0.25 mg/l Pb(NO₃)₂(1/20 of the 96-hour LC₅₀). The third group (Si-MNPs) was exposed to silica-stabilized magnetite nanoparticles at a concentration of 1 mg/l, and the fourth group (Pb + Si-MNPs) was exposed simultaneously to Pb(NO₃)₂and Si-MNPs at the same concentrations as the second and third groups. Throughout the experimental period, no mortalities or abnormal clinical observations were recorded in any of the treated groups, except for melanosis and abnormal nervous behavior observed in some fish in the Pb group. After three weeks of sublethal exposure, we analyzed hepatorenal indices, oxidative stress parameters, and genotoxicity. Values of alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), urea, and creatinine were significantly higher in the Pb-intoxicated groups compared to the control and Pb + Si-MNPs groups in both fish species. Oxidative stress parameters showed a significant decrease in reduced glutathione (GSH) concentration, along with a significant increase in malondialdehyde (MDA) and protein carbonyl content (PCC) concentrations, as well as DNA fragmentation percentage in the Pb group. However, these values were nearly restored to control levels in the Pb + Si-MNPs groups. High lead accumulation was observed in the liver and gills of the Pb group, with the least accumulation in the muscles of tilapia and catfish in the Pb + Si-MNPs group. Histopathological analysis of tissue samples from Pb-exposed groups of tilapia and catfish revealed brain vacuolation, gill fusion, hyperplasia, and marked hepatocellular and renal necrosis, contrasting with Pb + Si-MNP group, which appeared to have an apparently normal tissue structure.Conclusions: Our results demonstrate that Si-MNPs are safe and effective aqueous additives in reducing the toxic effects of Pb (NO₃)₂on fish tissue through the lead-chelating ability of Si-MNPs in water before being absorbed by fish.

This study was conducted on 70 diseased Pangasius hypophthalmus fish collected from different Pangasius fish farms in Egypt. Bacteriological examination revealed the isolation of P. aeruginosa that was biochemically confirmed using MALDI-TOF MS and VITEK 2 compact system. The prevalence and virulence of Pseudomonas aeruginosa were estimated genotypically using species-specific 16S rDNA gene, OprL and ToxA virulent genes for detection of pathogenic strains followed by sequencing analysis. Pathogenicity of isolated Pseudomonas aeruginosa was confirmed by experimental intraperitoneal injection of healthy Pangasius hypophthalmus with positively virulent strains resulting in high mortalities among injected fish.

This study aimed to assess the in vitro and in vivo disinfectant potential of peracetic acid (PAA) (1 mg/L) and hydrogen peroxide (H₂O₂) (20 mg/L) on the physicochemical and microbiological water quality parameters of fish aquaria, the microbial density of Nile tilapia muscular tissue, fish hepatic cortisol levels, and antioxidant biomarkers. In vitro, PAA and H₂O₂ reduced A. hydrophila colony viability by 5 log units after 30 and 5 min of contact time, respectively. PAA and H₂O₂ were added to aquaria water twice a week for the three-week experiment. Increased fish escape reflexes were observed only in the PAA group, which returned to normal within 10 min. No mortalities were reported in either the PAA or H₂O₂ groups. An in vivo experimental challenge with a pathogenic strain of A. hydrophila revealed a 20% reduction in mortality in the PAA group, with no mortalities in the H₂O₂ group. Cortisol levels and antioxidant markers were measured to assess the impact of PAA and H₂O₂ on fish health. Cortisol levels in the PAA and H₂O₂ groups were significantly higher than in the control group after disinfectant exposure, but they progressively returned to normal. A significant reduction in superoxide dismutase (SOD) and catalase (CAT) activity, along with considerably higher glutathione peroxidase (GPx) and malondialdehyde (MDA) enzymatic activity, was observed in the PAA and H₂O₂ groups compared to the control group. A substantial increase in total antioxidant capacity (TAC) was recorded in the PAA group. Physicochemical analyses revealed reduced pH and increased dissolved oxygen levels in the PAA and H₂O₂ groups. Microbiological analyses showed a significant reduction in bacterial density in water by 64% and 76% after 30 min of exposure to PAA and H₂O₂, respectively, with a non-significant increase in microbial count after bacterial challenge. Additionally, aerobic bacterial count, Aeromonas spp., and psychotropic bacterial count in fish muscle showed a significant reduction in the H₂O₂ group compared to the PAA and control groups before and after infection. The study concludes that regular application of PAA and H₂O₂ can temporarily reduce bacterial load in aquaria and fish muscle, regulate stress responses, and improve fish health by reducing A. hydrophila-induced infections and improving survival.

Nowadays, Qarun and Wadi El-Rayan lakes are exposed to adverse ecological changes that have led to the loss of fish stocks. In this study, we recorded the most common parasitic infestations in these lakes regarding bad water quality parameters and the associated parasitological and pathological effects. A total of 274 fish species were categorized into 205 Tilapia zillii, and 69 Solea aegyptiaca were randomly collected from Wadi El Rayan lakes; private fish farms and Shakshouk area of Lake Qarun in Fayoum governorate, Egypt. Total prevalence of parasitic infection was 33.9 %. All of the examined fish were positive for one or two mixed parasitic infections. Trichodina spp., Gyrodactylus spp., Cichlidogyrus tilapiae, Centrocestus formosanus encysted metacercaria and Livoneca redmanii were detected in 4.3%, 11.2 %, 13.6 %, 14.6% and 4.3% of infected fishes respectively. The immunological response of fish to parasitism was detected via the upregulation in levels of TNFα and IL-1β genes with significant differences (P =0.000). The obtained physicochemical water parameter results from studied places indicate that ammonia, nitrite, nitrate, and phosphate concentrations were above the specified permissible limits. The histopathological lesions associated with parasitic infestation described severe hyperplasia, degeneration and necrosis of gill lamellae; congestion of branchial blood vessels, associated with the presence of Trichodina spp., and encysted C. formosanus in gills. These all highlight how important it is to comprehend how these parasites can affect fish health, productivity and the aquaculture industry. However, the presence of these parasites in fish-rearing water requires more financial and management efforts.