Egyptian propolis extracts have an activity on cryptosporidiosis in rats. Moreover, propolis modulated the immunity in dexamethasone-immunosuppressed rats.

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‐1β), and transforming growth factor‐beta 1 (TGF‐β1) 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.

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The present study investigated the protective effects of dietary Allium cepa against Saprolegnia parasitica infections and the amelioration of cadmium-induced immunosuppression in Oreochromis niloticus. Saprolegnia isolates were recovered during an outbreak of saprolegniasis in farmed O. niloticus raised in a poor aquatic environment. Isolates were identified phenotypically as S. parasitica. Results were confirmed further by ITS gene sequencing. Four fish groups were kept in water with cadmium (1.5 mg/L) and fed for 30 days on a diet supplemented with crude or alcoholic extracts of A. cepa using two concentrations (0.5% or 1%). Positive (with Cd) and negative (without Cd) control fish groups were given the basal diet. The 96 h LC50 value of Cd in tilapia was (15.1 mg/L Cd). Fish exposed to Cd showed poor growth performance parameters, abnormal biochemical measurements, impaired immunological responses, and high oxidative stress indicators. Feeding tilapia on A. cepa-supplemented diets enhanced their growth performance (WG, SGR) and improved the nonspecific immune responses (WBCs, total protein, globulins, lysozyme, myeloperoxidase, and antiproteases). The inclusion of A. cepa in the diets reduced the oxidative stress (GST, SOD) and significantly decreased fish mortality after the challenge with S. parasitica. Dietary supplementation with A. cepa reduced cadmium accumulation in fish organs and up-regulated IL-1β and IFNɣ levels. The most favorable benefits were obtained by the addition of 0.5% A. cepa extract. Our results highlight the immunostimulatory properties of A. cepa dietary supplementation for farmed tilapia and recommend its use prophylactically to control saprolegniasis and mitigate cadmium adverse effects.