Olive leaves are an immense source of antioxidant and antimicrobial bioactive constituents. This study investigated the effects of dietary incorporation of olive leaf extract (OLE) on the growth performance, hematobiochemical parameters, immune response, antioxidant defense, histopathological changes, and some growth- and immune-related genes in the common carp (Cyprinus carpio). A total of 180 fish were allocated into four groups with triplicate each. The control group received the basal diet without OLE, while the other three groups were fed a basal diet with the OLE at 0.1, 0.2, and 0.3%, respectively. The feeding study lasted for 8 weeks, then fish were challenged with Aeromonas hydrophila. The results revealed that the group supplied with the 0.1% OLE significantly exhibited a higher final body weight (FBW), weight gain (WG%), and specific growth rate (SGR) with a decreased feed conversion ratio (FCR) compared to the other groups (p < 0.05). An increase in immune response was also observed in the fish from this group, with higher lysosome activity, immunoglobulin (IgM), and respiratory burst than nonsupplemented fish, both before and after the A. hydrophila challenge (p < 0.05). Similarly, the supplementation of the 0.1% OLE also promoted the C. carpio’s digestive capacity pre- and post-challenge, presenting the highest activity of protease and alkaline phosphatase (p < 0.05). In addition, this dose of the OLE enhanced fish antioxidant capacity through an increase in the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) and decreased hepatic lipid peroxidation end products (malondialdehyde—MDA), when compared to the control group, both pre- and post-infection (p < 0.05). Concomitantly with the superior immune response and antioxidant capacity, the fish fed the 0.1% OLE revealed the highest survival rate after the challenge with A. hydrophila (p < 0.05). A significant remarkable upregulation of the hepatic sod, nrf2, and protein kinase C transcription levels was detected as a vital approach for the prevention of both oxidative stress and inflammation compared to the infected unsupplied control group (p < 0.05). Interestingly, HPLC and UPLC-ESI-MS/MS analyses recognized that oleuropein is the main constituent (20.4%) with other 45 compounds in addition to tentative identification of two new compounds, namely oleuroside-10-carboxylic acid (I) and demethyl oleuroside-10-carboxylic acid (II). These constituents may be responsible for the OLE exerted potential effects. To conclude, the OLE at a dose range of 0.66–0.83 g/kg w/w can be included in the C. carpio diet to improve the growth, antioxidant capacity, and immune response under normal health conditions along with regulating the infection-associated pro-inflammatory gene expressions, thus enhancing resistance against A. hydrophila.

Vibrio parahaemolyticus and Aeromonas hydrophila are major public health problems and the main cause of bacterial disease in Nile tilapia (Oreochromis niloticus). This study was conducted to determine the prevalence, antibiotic resistance and some virulence genes of both V. parahaemolyticus and A. hydrophila isolates from Nile tilapia. From Manzala Farm at Dakahlia governorate, 250 freshwater fish samples were collected. The confirmed bacterial isolates from the examined Nile tilapia samples in the study were 24.8% (62/250) for V. parahaemolyticus and 19.2% (48/250) for A. hydrophila. multiplex PCR, revealing that the tlh gene was found in 46.7% (29/62) of V. parahaemolyticus isolates, while the tdh and trh virulence genes were found in 17.2% (5/29). Meanwhile, 39.5% (19/48) of A. hydrophila isolates had the 16s rRNA gene and 10.5% (2/19) had the aerA and ahh1 virulence genes. The Multiple Antibiotic Resistance indices of V. parahaemolyticus and A. hydrophila were 0.587 and 0.586, respectively. In conclusion, alternative non-antibiotic control strategies for bacterial infections in farmed fish should be promoted to avoid multidrug-resistant bacteria. Therefore, it is suggested that farmers should be skilled in basic fish health control and that molecular detection methods are more rapid and cost-effective than bacteriological methods.

Thiacloprid (TH) is a neurotoxic agricultural insecticide and potential food contaminant. The purpose of this study was to investigate the relationship between TH exposure and memory dysfunction in rats, as well as the potential protective effect of piracetam and piracetam-loaded magnetic chitosan nanoparticles (PMC NPs). Rats were divided into five equal groups (six rats/group). The control group received saline. Group II was treated with PMC NPs at a dose level of 200 mg/kg body weight (Bwt); Group III was treated with 1/10 LD₅₀of TH (65 mg/kg Bwt); Group IV was treated with TH (65 mg/kg Bwt) and piracetam (200 mg/kg Bwt); Group V was co-treated with TH (65 mg/kg Bwt) and PMC NPs (200 mg/kg Bwt). All animal groups were dosed daily for 6 weeks by oral gavage. Footprint analysis, hanging wire test, open field test, and Y-maze test were employed to assess behavioral deficits. Animals were euthanized, and brain tissues were analyzed for oxidative stress biomarkers, proinflammatory cytokines, and gene expression levels of glial fibrillary acidic protein (GFAP), amyloid-beta precursor protein (APP), B-cell lymphoma 2 (Bcl-2), and caspase-3. Brain and sciatic nerve tissues were used for the evaluation of histopathological changes and immunohistochemical expression of tau protein and nuclear factor kappa B (NF-κB), respectively. The results revealed that TH-treated rats suffered from oxidative damage and inflammatory effect on the central and peripheral nerves. The administration of PMC NPs considerably protected against TH-induced neuronal damage, increased antioxidant enzyme activity, decreased inflammatory markers, and improved behavioral performance than the group treated with piracetam. The neuroprotective effect of PMC NPs was mediated through the inhibition of GFAP, APP, caspase-3, Tau, and NF-κB gene expression with induction of Bcl-2 expression. In conclusion, TH could induce oxidative stress, inflammatory and neurobehavior impairment in rats. However, PMC NPs administration markedly mitigated TH-induced brain toxicity, possibly via oxidative and inflammatory modulation rather than using piracetam alone.

This study evaluated the effects of dietary organic acid (OA) blend on hemato-immunological responses, reproduction capacity, gene expression, and histological features of red tilapia (Oreochromis niloticus × O. mossambicus) broodstock. Four diets were formulated, containing 0 (control), 2, 3, and 4 g OAs kg⁻¹. The diets were fed to triplicate groups (n = 3) of red tilapia broodstock (75 ± 5.56 g( (mean ± standard deviation (SD)) stocked in 10-m³ concrete tanks at a male to female ratio of 1:3, to satiation, twice a day, for 8 weeks. At the end of the feeding trial, fish in each tank were collected, counted, and weighed. Blood samples were collected from five fish from each tank and used for the determination of hematological and biochemical parameters. The fish were then dissected to study the reproductive performance and reproduction-related genes. The red blood cells (RBCs), hemoglobin (Hb), packed cell volume (PCV%), mean corpuscular volume (MCV), and lysozyme activity were significantly increased (P < 0.05) with increasing dietary OAs to 4 g kg⁻¹. Mean corpuscular hemoglobin (MCH), white blood cells (WBCs), total protein, albumin, and globulin), and digestive enzyme activity values leveled off or slightly decreased (P > 0.05) at OA levels above 3 g kg⁻¹. Optimum liver enzyme activity was obtained at 2 g kg⁻¹ OA. The reproductive hormones: testosterone (T), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and progesterone (Prog), organo-somatic index (GSI), reproductive performance, and the expression of reproductive genes (vasa, nanos1a, nanos2, dnd1, pum1, amh, and VTG) exhibited dose-dependent responses (P < 0.05), suggesting that 4 g OA kg⁻¹ boosted the optimum reproductive performance. In conclusion, about 2–3 g OA kg⁻¹ diet can improve the hemato-biochemical parameters, immune response, antioxidant status, and digestive enzyme activity in red tilapia broodstock, whereas 4 g kg⁻¹ could accelerate their reproductive performance through upregulation of reproductive genes.