Immune-biochemical response and immune gene expression profiling of Labeo rohita fingerlings fed with ethanolic tea leaf extracts and its survivability against Aeromonas hydrophila infection.

The present study was conducted to evaluate the immunostimulatory effect of tea leaf extract (Camellia sinensis) on Labeo rohita and its resistance against Aeromonas hydrophila infection. The ethanolic extract of green tea (GTEE) was found to be the most potent as compared to other solvent extract which was used for further study. It was used to evaluate immune-biochemical response of L. rohita fingerlings, fed with tea leaf extract (control- 0.0%, 0.2% (T1), 0.4% (T2), 0.8% (T3) and 1% (T4) of GTEE kg-1 feed). Different biochemical parameters like glucose, ALP, GPT, GOT, and immunological parameters like lysozyme activity, NBT, anti-protease activity, myeloperoxidase activity, plasma protein, and immune relevant genes (IL-10, C3, Lysozyme G type and iNOS) expressions were carried out. The immunological parameters such as lysozyme activity, NBT and myeloperoxidase activity showed significantly high value once fed with GTEE incorporated diets. Significant up-regulation of immune genes indicated the enhancement of immune response at molecular level. The biochemical parameters were found to be significantly decreasing, indicating that the extract had hepato-protective effect and can help to overcome stress. The fish, fed with GTEE incorporated diets, showed resistance against A. hydrophila when compared with the control group. 0.2% GTEE showed the highest post-challenged survival (76.67%). From the present study, it is concluded that GTEE @ 0.2% can be used as potent immunostimulant as a sustainable alternative prophylactic and therapeutic agent in aquaculture.

Immunity augmentation in Botia dario (Hamilton, 1822) through carotenoid: a dietary approach.

The immunity and health status of ornamental fish is an important aspect, as they are kept in a confined environment and various stressful conditions which lead to depletion of overall colourful appearance and mortality. The carotenoids can act as immunity boosters in captive aquarium system and may be supplemented in the feed as aquarium fish have no access to natural carotenoids. The study aimed to assess the role of carotenoid on the immunity of B. dario. Marigold petal meal is an important source of carotenoids and used in experimental diets. Four immunogenes namely IL20, TLR9, TRAIL, and Nramp in B. dario were characterized and also studied for their relative expression in the kidney after feeding the fish with marigold petal meal supplemented diet. The expression pattern of the genes was compared with the fish of nature. The IL20 and Nramp gene were upregulated significantly (p < 0.05) in the fish of nature as compared to the experimental fish at the 60th day of feeding carotenoid-rich diet. But the TLR9 and TRAIL gene was upregulated significantly (p < 0.05) in experimental fish as compared to nature. The haematological parameters of fish after feeding with the experimental enriched diet for 60 days also confirmed the role of carotenoids in immunity.

Effect of miconazole nitrate on immunological response and its preventive efficacy in Labeo rohita fingerlings against oomycetes Saprolegnia parasitica.

This study evaluated the effect of sublethal doses of antifungal drug miconazole nitrate (MCZ) on immunological responses and its role as a prophylactic drug against S. parasitica in Labeo rohita fingerlings. Fish were fed with sublethal doses of MCZ, that is, T1-6.30 mgMCZ kgBW-1 , T2-12.61 mgMCZ kgBW-1 and T3-25.22 mgMCZ kgBW-1 , and sampling was done at different time intervals for 240 hr. Immunological parameters viz. lysozyme activity, oxygen radical production and plasma antiprotease activity showed significant enhancement (p < 0.05) in fish fed with T2 and T3 doses. Expression of immune-relevant genes such as TLR-22 and ß2-M showed significantly higher expression at 6 hr and 24 hr of sampling in both liver and head kidney. However, these genes showed a downregulation after 120 hr of sampling in both the tissues. Preventive efficacy study showed that single dose of MCZ provides protection against oomycetes up to the fourth day of infection. Significantly higher mortality was observed in control diet-fed fish as compared to fish fed with MCZ medicated diet. Thus, it can be concluded that the MCZ can act as a potent antifungal agent for preventing oomycetes infection as well as to enhance the immune response.