Protection of crucian carp (Carassius auratus Gibelio) against septicaemia caused by Aeromonas hydrophila using specific egg yolk immunoglobulins

Egg yolk immunoglobulins (IgY) were obtained from laying hens immunized with inactivated Aeromonas hydrophila. The purified IgY was shown to inhibit the growth of A. hydrophila in vitro and the optimum concentration for inhibition of A. hydrophila-specific IgY was 75mg mL1. In a subsequent challenge trial, 100 carp (200 similar to 250g) were assigned to one of ten tanks with ten carp per tank. The fish in one tank were unchallenged whereas the remaining 90 fish were injected intraperitoneally with 100L of A. hydrophila at a concentration of 108cfumL1. For the next 21days, all fish were moved in their respective groups to a clean tank for 20minday1. The fish in four tanks (one unchallenged tank and three challenged tanks) received no treatment whereas the fish in the remaining six tanks were immersed in either 0.5gL1 aqueous nonspecific IgY (N=3) or 0.5gL1 aqueous specific IgY (N=3). Haemoglobin concentrations, white and red blood cell numbers as well as the mortality of specific IgY-treated fish were significantly different from those of the control. These results suggest that passive immunization by immersion with pathogen-specific IgY may provide a valuable treatment for A. hydrophila infection in carp.