Search

Immunomodulation is one of the useful tools to prevent diseases in aquaculture. In this study, the immunomodulatory effects of vitamin-E (100 mg/kg feed) and commercial probiotic consortia, Rhodomax™ (5 g/kg feed) on the innate immunity of Labeo rohita and their protective effect against Aeromonas hydrophila infection were evaluated and compared. Three groups of fish at 30 numbers/tank were fed with vitamin-E, probiotic and control diets at 3% body weight for 30 days, in triplicate. Following this, the fish of all groups were injected intramuscularly with A. hydrophila N10P at 2.40 × 107 cells/fish. The growth indices like specific growth rate (SGR) and feed conversion ratio (FCR) during the feeding and the non-specific immune responses during the feeding and post-challenge regimen were recorded. The dietary supplementation of vitamin-E and/or commercial probiotics caused significant improvements in the innate immunity of L. rohita compared to control. Nevertheless, the vitamin-E diet offered markedly better results in terms of SGR, FCR, ceruloplasmin, antiprotease, myeloperoxidase and phagocytic activities of L. rohita during the feeding and post-challenge regimen. While the respiratory oxidative burst activity was enhanced in probiotic diet-fed L. rohita only during the feeding regimen. All the immune parameters reached normalcy on day 15 post-injection with A. hydrophila. These findings revealed that supplementation vitamin-E at 100 mg/kg feed may improve the growth indices, prime the non-specific immune responses of L. rohita against A. hydrophila infection and enhance the overall health status than the tested commercial probiotics.

The study was conducted to evaluate the vaccination effects on rohu, Labeo rohita head kidney tissues while assessing the vaccine efficacy of Aeromonas hydrophila antigens. Six acclimatized rohu groups were immunized with three antigenic formulations (outer membrane proteins, somatic and whole-cell antigen) @ 200 µg/fish and also with equal volume of Freund's incomplete adjuvant (FIA), separately. Simultaneously, two non-vaccinated groups, i.e., injected with FIA (100µl), normal saline solutions (0.85%) and one control without injection were maintained for 28 days. All rohu were challenged with median lethal dose of A. hydrophila (2.85 × 106 cells/rohu) intraperitoneally. After 7 days, highest cumulative mortality (%) of ˃88% was found for all non-vaccinated groups. During histopathological observations in head kidney tissues of all treatment and control groups, numerous histopathological changes in the nephritic cells like mild loss of typical tubular epithelial lining, necrosis, thickening of renal epithelial lining, haemorrhages, inflammation, distorted and widening of the lumen with vacuolated surrounding and the constricted lumen of nephritic tubules were noticed for vaccinated rohu in contrast to non vaccinated groups before A. hydrophila challenge. In case of all non-vaccinated fish, including control, extensive degenerated and necrotized head kidney tissues were observed, whereas it was least observed in vaccinated rohu after 7 days A. hydrophila challenge. Results suggest that OMPs antigen along with FIA was the premier vaccine approach for improving resistance to Aeromonas disease and reduce mortality in rohu. Similarly, vaccination with all three antigenic formulations, preferably when applied along with FIA, can effectively protect the head kidney against A. hydrophila infection.