The purpose of this study was to determine the effect of aflatoxin B1 (AFB1) on immunity and hematological profile, RBC, WBC, Hb, serum protein, albumin-A, globulin-G, A/G ratio, phygocytic activity, nitro blue tetrazolium reduction and
challenge test against Aeromonas hydrophilla of apparently healthy 150 Nile tilapia Oreochromis niloticus weighed 23.42±1.2 gram. After 84 days of exposure to AFB1 100 and 20 μg/kg fish samples were collected then O. niloticus were treated with biological antitoxin for 3 days then samples were taken after stoppage the treatment
by 7 days. Immune activities and hematological profile were significantly (P ≤ 0.05) influenced in dose and duration of exposure dependent manner this was reflected in the health and growth performance of O. niloticus. Results indicated that improvements had achieved by lowering the AFB1 compained with biological treatment