Mohamed Abdalla Khallaf

Brown seaweed has gained special attention in aquaculture nutrition studies due to its functional bioactive compounds, such as polysaccharides. This study evaluated the functional potential of the brown seaweed, Ascophyllum nodosum , as a natural immunostimulant and growth promoter in Nile tilapia. A 74-day feeding experiment was conducted using 540 fingerlings (initial body weight 18.4 ± 0.2 g), randomly allocated to six dietary treatments (0, 0.5, 1.0, 1.5, 2.0, and 2.5 g AS/kg diet) in six triplicate groups. Fish were reared under optimal water conditions. Growth performance improved significantly with AS supplementation, achieving optimal responses at approximately 1.9 g/kg, as reflected in superior specific growth rate and feed conversion ratio. Hepatic antioxidant defenses, superoxide dismutase, catalase, glutathione peroxidase, and total antioxidant capacity were markedly enhanced, whereas malondialdehyde levels declined, signifying reduced oxidative stress. Serum lysozyme activity, bactericidal activity, and total protein levels increased notably, supported by the upregulation of immune-related genes ( IL-1β , TLR2 , lysozyme , hepcidin ). Upon Aeromonas hydrophila challenge, fish receiving diets with 1.0–2.0 g AS/kg exhibited significantly higher survival, confirming strengthened immune protection. Cooperatively, A. nodosum supplementation reinforced growth, antioxidant responses, and disease resilience in Nile tilapia, highlighting its promise as an eco-friendly nutraceutical for sustainable aquaculture development.

The present study evaluated the impacts of powdered Astragalus membranaceus extract (AME) on the growth, physiological responses, and serum immunity of Pangasianodon hypophthalmus juveniles. Four test diets were formulated to include varying AME levels as 0.0 (control), 1.5 (AME1.5), 3.0 (AME3.0), and 4.5 (AME4.5) g/kg. Fish weighing approximately 11.50 g were stocked into four triplicate groups and hand-fed on the test diets three times daily for two months. At 60 days post-feeding, the growth performance, including weight gain and the specific growth rate, was increased quadratically (R² > 0.90) with increasing AME inclusion levels. An improvement in the feed intake and feed conversion ratio were also noticed in groups fed at different AME levels. The whole-body and amino acid composition were unaffected by the test diets. A significant quadratic trend in the digestive enzymes (lipase, α-amylase, and protease) was found along with increasing AME inclusion levels. Liver enzymes associated with liver functions were improved by AME dietary inclusion levels. Meanwhile, the blood urea nitrogen, uric acid, and creatinine values were unaffected by AME dietary inclusion. On the other hand, serum immunity (lysozyme and total Igs) was elevated with a significant quadratic trend along with increasing AME dietary inclusion levels. Liver MDA levels decreased with increasing AME levels. Liver CAT, GPx, and SOD enzyme activities demonstrated a significant increasing trend along with dietary AME inclusion. The aforementioned effects of dietary AME on P. hypophthalmus health underpinned the potentiality of AME to be used as a phyto-additive to improve the functionality of aquafeed.

Streptococcus agalactiae has been described as one of the most serious bacterial diseases in tilapia culture. This study investigated the isolation and characterization of Streptococcus agalactiae from a condition of mass mortality in farmed Oreochromis niloticus at Baltim region, Kafr El-Sheikh governorate, Egypt during the summer of 2019, and the effectiveness of locally prepared bacterin for prevention of streptococcal disease. Infected fish showed corneal opacity, congestion of spleen, liver, and kidney, the abdominal space filled with watery and bloody ascites, and light-colored nodules on the kidneys, spleen, or liver. Water qualities were measured parallel to the fish sample. S. agalactiae isolates were identified by phenotypic and biochemical VITEK II methods. Ampicillin, Colistin sulfate, would appear as the best antibacterial agents to use in the treatment. The relative level of protection value was 70% in Oreochromis niloticus challenged with a virulent strain of S. agalactiae (107 CFU /1 ml) and vaccinated with locally prepared killed bacterin. Histopathological investigations revealed congested blood vessels in all organ's specimens examined, inflammatory cells infiltration, degenerative changes, different stages of necrosis of the liver, and generalized meningoencephalitis of the brain. The current study recommended that S. agalactia induced many problems in tilapia culture in presence of bad water quality during the summer season, and the vaccination program gives good results and high protection which may be a useful method for the prevention and control of streptococcal infection.

The current investigation assessed the impacts of sub-lethal concentrations of silicon dioxide nanoparticles (SiO₂NPs) on hepato-renal functions, histopathological characteristics, and gene transcription in gills and liver of Nile tilapia juveniles. Fish were exposed to 20, 40, and 100 mg/L of SiO₂NPs for 3 weeks. Pairwise comparisons with the control group showed a significant dose-dependent elevation in serum ALP, ALT, and AST enzyme activities as well as blood urea and creatinine levels in SiO₂NP-intoxicated groups. Exposure to 100 mg/L SiO₂NPs significantly upregulated expression of HSP70, TNF-α, IL-1β, and IL-8 genes in the gills as compared to the control group. Moreover, exposure to 100 mg/L SiO₂NPs significantly upregulated the expression SOD, HSP70, IL-1β, IL-8, and TNF-α genes in the hepatic tissues as compared to the control group. Exposure of fish to 20 mg SiO₂NPs/L significantly increased the mRNA expression levels of IL-12 in both the gills and liver tissues. Notably, all tested SiO₂NP concentrations significantly upregulated the transcription of CASP3 gene in gills and liver of Nile tilapia as compared to the control group. Interestingly, varying histopathological alterations in renal, hepatopancreatic, and branchial tissues were observed to be correlated to the tested SiO₂NP concentrations. In conclusion, our results provide additional information on the toxic impacts of SiO₂NPs in Nile tilapia at the hematological, tissue, and molecular levels.

In the present study, fish were exposed to sub-lethal doses of CuONPs (68.92 ± 3.49 nm) (10 mg/L, 20 mg/L, and 50 mg/L) for a long exposure period (25 days). Compared to the control group (0.0 mg/L CuONPs), a significant dose-dependent elevation in blood urea and creatinine values, serum alanine transaminase, aspartate transaminase, and alkaline phosphatase enzyme activities were evident in CuONPs-exposed groups (p < 0.05). Fish exposure to 50 mg/L CuONPs significantly upregulated the transcription of pro-inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, interleukin 12, and interleukin 8), heat shock protein 70, apoptosis-related gene (caspase 3), and oxidative stress-related (superoxide dismutase, catalase, and glutathione peroxidase) genes in liver and gills of the exposed fish in comparison with those in the control group (p < 0.05). Moreover, varying histopathological injuries were noticed in the hepatopancreatic tissues, posterior kidneys, and gills of fish groups correlated to the tested exposure dose of CuONPs. In summary, our results provide new insights and helpful information for better understanding the mechanisms of CuONPs toxicity in Nile tilapia at hematological, molecular levels, and tissue levels.

Trichodinids are commensal ectoparasitic protozoa, having direct life cycle and may become pathogenic hindering with respiration and feeding of fishes. The study aimed to determine the seasonal dynamics of Trichodina spp. infecting Oreochromis niloticus and their Histopathological effects. Microscopic examination of gills of 747 Tilapia at different localities of Behera province, Egypt was carried out all over one year extended from January to December 2019. The Histopathological examination of infected gills was performed. The results showed that, the prevalence of Trichodina spp. was 4.36%. The locality and weights of examined fish had no significance on the occurrence of Trichodina spp. The infection rate was affected significantly by the season. The highest infection was recorded in autumn whereas the lowest infection was in summer. Moreover, the measurements and morphological description of recovered Trichodina spp. were reported. Trichodina spp. appeared as multiple ring-shaped structures attached to the supporting gill structure and surrounded by few inflammatory cells and there was congestion, fusion, thickening and distortion of gills secondary lamellae.

Determination of numbers of T cell subsets in tissues is important to assess the functional maturity of the immune system. The distribution of T cells in lymphoid tissues during ontogenic development has been examined in several fish species using pan-T cell markers. However, information on the age-related changes in the number of T cell subsets in tissues is limited due to the lack of antibodies against CD4 and CD8 in fish. In the present study we examined the percentage dynamics of CD4-1⁺ and CD8α⁺ cells in various tissues accompanied with age of ginbuna crucian carp using flow cytometry. We found rapid increases in both CD4-1⁺ and CD8α⁺ T cells up until 6 months post-hatch (mph). CD4 and CD8 double-positive cells (DP cells) are present only in the thymus and DP cells increased, while double negative cells decreased, in fish up to 3-6 mph. The percentages of CD4-1⁺ T cells were always higher than those of CD8α⁺ T cells in the various tissues examined, except for the thymus and intestine. In contrast, significantly higher percentages of CD8α⁺ T cells than CD4-1⁺ T cells were found in the intestine during the period between 6 mph and 2 years post-hatch.