The present study aimed evaluates the antibacterial, biochemical, and heamatological activities of neem (Azadirachta indica) leaves on the health statues of catfish (Clarias gariepinus) experimentallyinfectedwith Aeromonas hydrophila.The bacteriological examination of naturally infected Clarias gariepinus revealed that,the most prevalent isolates were Aeromonas hydrophila 13% followed by Pseudomonas fluorescens 12%. Two hundred and forty apparently healthy Clarias gariepinus were divided into 8 subgroups for experimental purpose. Experimental infection was done by intraperitoneal (IP) injection of Aeromonas hydrophila and examination of the infected and control fish in the 1st, 2nd and 3rd weeks post infection. The antibacterial activity of neem leaves reduced the mortality rate from 80% in an infected nontreated subgroup to 26.6% and 30% in subgroups that infected and treated with neem and oxytetracycline combination and treated with neem only respectively. Subgroup infected and treated with neem had lower total bacterial count (TBC) (1x104CFU/ml) than subgroup infected and treated with oxytetracycline (7x105CFU/ml). Heamatological parameters and serum biochemical index in both infected subgroups treated with neem or treated with neem and oxytetracycline combination were approximately similar to noninfected nontreated subgroups (negative control normal subgroup). We could conclude
that neem leaves-supplemented diets had a potential effect in reduce mortality and bacterial infection in Clarias gariepinus