Investigating the immunomodulatory and haemato-protective roles of curry leaf ethanolic extract (Murraya koenigii) in Labeo rohita fingerlings Infected with Aeromonas hydrophila.

Aeromonas hydrophila is a highly virulent pathogen that causes substantial mortality in Labeo rohita fingerlings. In our present study, phytochemical analysis of curry leaf (Murraya koenigii) confirmed the presence of bioactive compounds such as alkaloids, phenolics, flavonoids, and terpenoids, known for their potent antimicrobial and immunomodulatory properties. This study evaluates the immunomodulatory and haemato-protective effects of curry leaf (Murraya koenigii) ethanolic extract (CLEE) against Aeromonas hydrophila infection in Labeo rohita, focusing on haematological, biochemical, and immunological parameters. In infection trials, survival rates were higher for feeds treated with 1 g, 2 g, and 3 g of CLEE were 46.67%, 68.89%, and 66.67%, respectively, compared to 36.67% in the bacterial control group. Haematological results showed a significant dose-dependent increase in red blood cell (RBC) count, haemoglobin, and white blood cell (WBC) count. The CLEE 2 g and CLEE 3 g groups had significantly (P < 0.05) higher RBC counts of 1.08 ± 0.01^a × 10¹²/L and 0.99 ± 0.07^a × 10¹²/L, compared to 0.49 ± 0.09^c × 10¹²/L in the bacterial control. Biochemical analysis revealed significant (P < 0.05) reductions in serum glucose, total protein, and liver enzymes (SGOT, SGPT, ALP). Specifically, serum glucose levels significantly (P < 0.05) decreased from 99.93 ± 3.04^a mg/dL in the bacterial control to 75.52 ± 1.68^d mg/dL in the CLEE 2 g and 79.89 ± 1.86^c mg/dL in the CLEE 3 g. Antioxidant enzyme activities, including superoxide dismutase (SOD), catalase, and myeloperoxidase activity (MPO), were significantly (P < 0.05) higher in CLEE-treated groups. Histopathological analysis showed partial regeneration of liver and kidney tissues, especially in the CLEE 2 g and CLEE 3 g groups. These findings suggest that CLEE effectively mitigates A. hydrophila infection, improves immune function, reduces oxidative stress, and promotes tissue recovery in L. rohita fingerlings. This study addresses a significant research gap, offering insights into CLEE's potential applications in aquaculture and its therapeutic efficacy in combating bacterial infections.