The present study investigated the effects of dietary supplementation of nanocurcumin (NCur = 150 ppm) in African catfish feed for 15 days along with two doses of florfenicol—a therapeutic dose (FFC1 = 10 mg/kg.BW) and a high dose (FFC2 = 30 mg/kg.BW). Serum biochemical parameters and histopathological changes in liver and kidney tissues were determined post-feeding. Additionally, fish were experimentally challenged with a virulent strain of Aeromonas veronii to explore the fish’s capacity to resist infections. Results indicated that the serum level of total protein was significantly elevated in the FFC2 + Ncur group compared with control, Ncur, and FFC2 groups. Total protein level was also higher in FFC1 + Ncur compared with that of the FFC1 group. Moreover, feeding NCur, FFC1 + Ncur, and FFC2 + Ncur resulted in a significant increase in globulin levels compared to control, FFC1, and FFC2-Fed groups. However, the albumin level was unaffected. Serum levels of AST, ALT, ALP, and urea significantly increased in FFC2-fed fish compared to controls indicating liver damage. The higher dosage of FFC2 induced histological alterations in the liver and kidney architecture, represented by a rupture of the central vein, cytoplasmic vacuolation, hepatocytes necrosis, and severe inflammation. Surprisingly, NCur inclusion improved most of the altered biochemical parameters and mitigated FFC-induced histological damage in the hepatic and renal tissues. Similarly, fish that were fed a combination of both FFC and Ncur showed a higher resistance when exposed to A. veronii infection, as the mortality rates were significantly lower than those of the control group. Our findings indicated that incorporating NCur into the diet can have multiple benefits for the sustainable aquaculture of African catfish. These advantages encompass mitigating drug-induced damage to the liver and kidney tissues, augmenting the therapeutic efficacy of FFC in a synergistic manner and providing protection against A. veronii infections.

The aim of this research was to estimate the immunopotentiation effect of brown algae Padina boergesenii water extract on Nile tilapia, Oreochromis niloticus through resistance to Pseudomonas putida infection. Gas Chromatography Mass Spectrometry was utilized to characterize the seaweed phytoconstituents. One hundred and twenty-six fish were divided in triplicates into two equal groups corresponding to two diet variants that used to feed Nile tilapia for 20 successive days: a basal (control), and P. boergesenii water extract supplemented group. Fish samples were collected at 10-days intervals throughout the experiment. Serum biochemical constituents, total antioxidant capacity (TAC), and some immune related genes expression of the spleen and intestinal tissues of experimental fish were studied, as well as histological examination of fish immune tissues. Moreover, following 20 days of feeding, the susceptibility of Nile tilapia to P. putida infection was evaluated to assess the protective effect of the used extract. The findings indicated that the studied parameters were significantly increased, and the best immune response profiles were observed in fish fed P. boergesenii water extract for 20 successive days. A bacterial challenge experiment using P. putida resulted in higher survival within the supplemented fish group than the control. Thus, the lowered post-challenge mortality of the fish may be related to the protection provided by the stimulation of the innate immune system, reduced oxidative stress by higher activity of TAC, and elevated levels of expression of iterleukin-1beta (IL-1β), beta-defensin (β-defensin), and natural killer-lysin (NKl). Moreover, the constituents of the extract used showed potential protective activity for histological features of the supplemented fish group when compared to the control. Collectively, this study presents a great insight on the protective role of P. boergesenii water extract as an additive in Nile tilapia feed which suggests its potential for improving the immune response against P. putida infection.

Objective: During Egypt's hot summer season, Aeromonas veronii infection causes catastrophic mortality on Nile Tilapia Oreochromis niloticus farms. Egypt is ranked first in aquaculture production in Africa, sixth in aquaculture production worldwide, and third in global tilapia production. This study aimed to investigate, at the molecular level, the early innate immune responses of Nile Tilapia to experimental A. veronii infection. Methods: The relative gene expression, co-expression clustering, and correlation of four selected immune genes were studied by quantitative real-time polymerase chain reaction in four organs (spleen, liver, gills, and intestine) for up to 72 h after a waterborne A. veronii challenge. The four genes studied were nucleotide-binding oligomerization domain 1 (NOD1), lipopolysaccharide-binding protein (LBP), natural killer-lysin (NKL), and interleukin-1 beta (IL-1β). Result: The four genes showed significant transcriptional upregulation in response to infection. At 72 h postchallenge, the highest NOD1 and IL-1β expression levels were recorded in the spleen, whereas the highest LBP and NKL expression levels were found in the gills. Pairwise distances of the data points and the hierarchical relationship showed that NOD1 clustered with IL-1β, whereas LBP clustered with NKL; both genes within each cluster showed a significant positive expression correlation. Tissue clustering indicated that the responses of only the gill and intestine exhibited a significant positive correlation. Conclusion: The results suggest that NOD1, LBP, NKL, and IL-1β genes play pivotal roles in the early innate immune response of Nile Tilapia to A. veronii infection, and the postinfection expression profile trends of these genes imply tissue-/organ-specific responses and synchronized co-regulation.

Background: Common carp is one of the most economically important freshwater fish species globally. Ammonia exposure, a frequent challenge in aquaculture, can lead to significant economic losses. This study investigated the impact of un-ionized ammonia (UIA) exposure on the expression profiles of three key genes in common carp fry: interleukin-1 beta (IL-1β), corticotropin-releasing hormone (CRH), and leptin a1 (Lep-a1). These genes are crucial indicators of immune response, stress regulation, and appetite control, respectively. Fish were exposed to 0.7 mg/L of UIA, and gene expression was analysed in liver and gill tissues at five time points (12 h, 2-, 4-, 7-, and 14-days of exposure) using quantitative real-time PCR (RT-qPCR). Results: Results demonstrated that expression levels of all three genes were significantly affected by exposure time and tissue type. IL-1β, CRH, and Lep-a1 were upregulated in both liver and gill tissues, with the liver consistently showing higher expression levels. Notably, significant positive correlations were observed between each pair of the three genes studied, suggesting a coordinated physiological response to ammonia stress. The liver emerged as a key organ in orchestrating the long-term adaptive response, while the gills exhibited a more acute, transient reaction. Conclusions: This study provides valuable insights into the molecular mechanisms underlying the physiological response of common carp to ammonia toxicity. The findings highlight the complex interplay between immune, stress, and metabolic pathways in coping with ammonia exposure. A deep understanding of these mechanisms could lead to improved management strategies in aquaculture and the development of potential biomarkers for assessing stress responses in fish populations.

This study was conducted to investigate the ability of common carp, Cyprinus carpio, to adapt to various salinity levels. Two experiments were conducted to study the effects of gradual increase of salinity on weight gain, survival, immunological and osmoregulatory responses and consequent resistance to Vibrio vulnificus infections in common carp. In the first experiment, sodium chloride was added to the water by 0.5ppt every two days to reach a final concentration of 4, 6 and 8ppt, and fish were sampled after 14 days. In the second experiment, sodium chloride was added by 0.5ppt every week to reach a final concentration of 6 ppt and fish were sampled after one month. Fish of the first experiment exposed to 8ppt salinity showed significant increase in all serum measurements and detrimental effects on weight gain and survival. In the second adaptation experiment, the unaltered glucose, cortisol and ions levels indicated that salinity up to 6ppt did not produce significant stress in common carp it decrease the mortality rate caused by V. vulnificus. The above results suggest that common carp, a freshwater fish, can withstand gradual increases of salinity of up to 6ppt, and thus can be raised in brackish water with little or no detrimental effects on growth and performance.