The Immuno-Responses of Eel (Anguilla japonica) against Edwardsiella anguillimortifera as Studied by the Immersion Method

Abstract

The immersion method for the immunization of eel (Anguilla japonica) with the pathogen, Edwardsiella anguillimortifera, was studied and the results are summarized as follows: (1) Using the immersion method the immune response of eels can be induced effectively. (2) The effect of the treatment of hyperosmotic solution on the immunization of eels against E. anguillimortifera was evaluated. Following hyperosmotic treatment in 5.32% NaCl bath for 3 min, the eels were then immunized by soaking in the bacterial suspension for 3 min with heatkilled or formalin-killed Edwardsiella. The maximum titers in 5.32% NaCl pretreated eels were 1024 and 256 respectively, at fifth week after immunization. However, the maximum titers in the other two groups without osmotic shock were 256 and 128 respectively, at fourth week and seventh week after immunization. (3) The cumulative mortality of the eels against E. anguillimortifera challenge was higher in both groups with hyperosmotic pretreatment even though both had higher antibody titers. (4) The opsonic index of serum of immunized eels was 5.29. (5) In comparison with the control eels, the phagocytosis of the peritoneal leukocytes of the immunized eels increased significantly and specifically. © 1981, The Japanese Society of Fish Pathology. All rights reserved.