Combined effect of a mixture of Bacillus species and vaccination on haemato‐biochemical parameters, immune response and transcriptomic changes of Nile tilapia challenged with <i>Streptococcus iniae</i>

Abstract

The aim of this study was to evaluate the effect of probiotic supplementation and vaccination on haemato-biochemical parameters, immune and transcriptomic response of Nile tilapia challenged with Streptococcus iniae for 90 days. A total of 144 fish (50 ± 0.32 g) were divided in triplicates into four groups. Fish of the first group received a basal diet and were kept as control group (CG). Fish of the second group (VG) received a basal diet and were intraperitoneally vaccinated with ME-VAC Aqua Strept® polyvalent vaccine (0.1 ml/100 g fish body weight). Those of the third group (PG) received a basal diet supplemented with Sanolife PRO-F® probiotic (0.02 g/kg feed). The fourth group (PVG) received a basal diet supplemented with Sanolife PRO-F® probiotic (0.02 g/kg feed) and were vaccinated with ME-VAC Aqua Strept® polyvalent vaccine. Results showed that simultaneous supplementation of probiotics and use of vaccines elevated haematological, biochemical and immune parameters suggestive of improved health and immunity of fish. Similarly, concomitant supplementation of probiotics and use of vaccines upregulated the expression patterns of immune-related genes, growth-regulating genes (IGF1 and GH), and feed intake gene (ghrelin) indicative of improved heath, feeding and growth of fish. Findings, therefore, confirm the synergistic effect of probiotics and vaccination in improving the health status and immunity of tilapia against Streptococcus iniae infection. Use of probiotics and vaccination appears to not only improve health, production, disease resistance and welfare of fish but also help achieve goals of global sustainable development agenda.