The present study was performed to determine the efficacy of
lipopolysaccharide (LPS) and
levamisole on immune response and
disease resistance in striped catfish and to compare their respective efficiency with the one of an
antibiotic treatment after
infection of fish by the bacteria Edwardsiella ictaluri. Fish were divided into 3 groups and each group was injected with LPS (3 mg/kg fish),
levamisole (5 mg/kg fish) or
phosphate buffer saline as control. At day 21st post
immunostimulant injection, fish were bled for assaying immunological variables and then challenged with E. ictaluri. Three days after
bacterial infection, an
antibiotic treatment was applied into fish subgroups and mortality was compared daily between
antibiotic treated and untreated fish until 2 weeks post-challenge. LPS and
levamisole significantly enhanced non-specific immune responses such as respiratory burst,
lysozyme and
complement activity in fish compared with control (p < 0.05). Respiratory burst and
complement activity significantly increased in
levamisole groups when compared with LPS groups while
lysozyme activity did not differ significantly between
immunostimulant treatments. Total
immunoglobulins significantly increased in
levamisole treatment compared with control. After challenge test, accumulated mortality was reduced significantly in both non-
antibiotic and
antibiotic subgroups of LPS and
levamisole compared with control. Moreover, no differences of mortality were observed between fish treated with
levamisole or LPS without
antibiotics and control fish treated with
antibiotics. These results support the possible replacement of
antibiotics in striped catfish farming by
immunostimulants such as
levamisole and LPS.