A comparison of total and specific immunoglobulin levels in healthy Atlantic salmon (Salmo salar L.) and in salmon naturally infected with Aeromonas salmonicida subsp. achromogenes.

Healthy Atlantic salmon and salmon with a history of chronic natural Aeromonas salmonicida subsp. achromogenes infection were compared with respect to total serum protein and the concentration and specificity of serum immunoglobulin. The immunoglobulin level was measured using competitive ELISA and the specific antibody activity against Aeromonas salmonicida subsp. achromogenes was measured using double sandwich ELISA. Significant elevation of serum protein and immunoglobulin concentration was observed in the infected salmon compared with the healthy fish. This was accompanied by weak anti-A. salmonicida activity in the infected fish which seemed to contribute to the raised immunoglobulin level to only a limited degree.