Physiological and microbiota profiling of African catfish ( Clarias gariepinus ) challenged with Bdellovibrio sp.: implications for safe pathogen control in fish production

This study evaluated the safety of Bdellovibrio as a biocontrol agent in African catfish (Clarias gariepinus) by assessing physiological parameters, including haemato-biochemistry, stress enzymes, nitric oxide, gut histology, and microbiota. African catfish were orally administered Bdellovibrio sp. PW6 at two dosages: a low dose of 8.5 × 104 PFU (plaque-forming unit)/mL (Bd104) and a high dose of 1.8 × 106 PFU/mL (Bd106). The experimental and control fish showed no statistically significant differences (p > .05) across all analyzed parameters, suggesting that Bdellovibrio sp. PW6 had no observable adverse effects on the experimental fish. Histological analysis revealed goblet cells and mucous secretions in the Bdellovibrio-fed fish, indicating protective inflammatory response unlike in the control. Probiotic Cetobacterium somerae dominated the gut of Bd104 fish. Overall, Bdellovibrio sp. PW6 can be safely administered to African catfish at the study doses.