Effect of β-glucan on the immune response of early stage of Anabas testudineus (Bloch) challenged with fungus Saprolegnia parasitica

The present study was carried out to study the effect of different dosages of beta-glucan suspension on immune response and disease resistance in Anabas testudineus spawns against a fungal pathogen Saprolegnia parasitica. Eight day old spawns were exposed for 3 h in four different dosages of beta-glucan suspension in phosphate buffered saline at the rate of 0, 5, 10, 15 mg l(-1). The cell suspension of spawn was assayed for total protein, acid phosphate, lysozyme, bactericidal and NBT activity. The spawns were then challenged with 3x10(5) CFU ml(-1) of S. parasitica. The survivability percentage and immunological parameters were assayed upto day 7. Exposure of fish for 3h to all the concentrations of beta-glucan recorded a significant enhancement in the immunological parameters such as lysozyme activity, bactericidal activity and NBT activity by the end of day 7. The challenge study indicated least mortality in the groups exposed to 10 mgl(-1) and 15 mgl(-1) but 15 mgl(-1) gives little higher survivability. Thus 3 h exposure of beta-glucan suspension could reduce the mortality and increase the immunity of A. testudineus spawns against S. parasitica.