he operation of the phagocytotic cells such as neutrophils and monocytes. The thrombocytes function in the clotting of blood (Fange, 1994). Another primary defence mechanism in fish is a humoral antibacterial component known as lysozyme a hydrolytic enzyme in the kidney, serum, mucus and neutrophils of most teleosts (Mock and Peters, 1990; Nowak, 2003), capable of cleaving the peptidoglycan layer of bacterial cell walls (Kuby 1997), especially gram positive bacteria species, but also works indirectly on Gram negative bacteria (Mock and Peters, 1990). Fish lysozymes have a broader function than mammalian, with activity against gram-negative and gram-positive bacteria (Grinde et al. 1988). Lysozyme is produced in different amounts in response to different diseases, and has therefore been used as a nonspecific immune indicator (Grinde et al. 1988). Mock and Peters (1990) express that an increase in the lysozyme concentration in fish blood is caused by infections or injections of foreign material.
             The aim of this experiment was to investigate the immune response of lysozyme activity and the percentages of white blood cells in Atlantic salmon, Salmo salar, infected with AGD, Neoparamoeba pemaquidensis, as compared with controls.
             The experiment was conducted at the aquatic centre, University of Tasmania, Launceston and consisted of two treatments: (1) a control- no treatment and (2) the treatment of salmon infected with AGD.
             The experiment involved thirty Atlantic salmon (Salmo salar), 100g ± 13.2g.Body weight (BW). The salmon, both control and treatment, were maintained in 4000 L Rathburn tanks acclimated to seawater at 18°C. Treatment tank was inoculated with gill-isolated Neoparamoeba sp. At 500 cellsL-1. Five salmon were sampled, three controls and three infected 12 days post inoculation. Salom were euthanased with Aqui-S for both leucocyte counts and lysozyme activity.
             Blood samples were taken from each fish from th...