LAUSR

Nanotechnology has become an important tool for fish disease prevention and treatment. The current study was carried out to evaluate the efficacy of dietary thyme essential oil (TEO) and its nano-emulsion (TEO-NE) for motile Aeromonas septicemia prevention (MAS) in Oreochromis niloticus after in vitro evaluation. Aeromonas hydrophila was isolated from naturally diseased Oreochromis niloticus and Clarias gariepinus showed signs of septicemia and congestion of internal organs. Prevalence of MAS among diseased O. niloticus and C. gariepinus was 86.9 and 44.4%, respectively. The obtained isolates were identified as Aeromonas hydrophila by molecular assay and found to be highly pathogenic as they contained hemolysin and cytotoxic enterotoxin virulence genes. Experimental infection and medial lethal concentration were performed and it was 1.5 × 104. TEO-NE was synthesized by ultrasonication and characterized by TEM, ATR-FTIR, and zeta potential. The antibacterial activity of TEO-NE was noticed at the least concentration during in vitro evaluation. TEO-NE succeeded in preventing MAS in dietary fed O. niloticus with no mortality compared to 10 and 80% O. niloticus groups fed TEO and positive control group, respectively. Dietary TEO-NE induced significant increase in IgM, IL-1β, and lysozyme. Liver and kidney functions were within the normal levels in groups fed TEO and TEO-NE.