Prophylactic effect of β(1,3)‐D‐glucan (laminaran) against experimental Aeromonas salmonicida and Vibrio salmonicida infections

Abstract

Immersion and intraperitoneal vaccination are the two most common and successful methods for vaccination of fish (Holm & Júrgensen 1987; Lillehaug 1989). Effective vaccines and the improvement of environmental conditions have dramatically reduced the amount of antibiotics used in aquaculture in Norway from 48.5 t in 1987 to 1.03 t in 1996. Nevertheless, the labour intensive process of vaccination and the often undesirable side‐effects of the adjuvants incorporated in injectable vaccines (Anderson 1992; Mulvey, Landolt & Busch 1995; Midtlyng, Reitan, Speilberg 1996), have resulted in a search for alternative approaches to achieve immune stimulation. Hence. there is growing interest in the development of immunomodulators that do not cause or have only minor unwanted effects on the host and preferably can be given as a feed additive. It is widely acknowledged that the beneficial (or in some instances undesirable) effects of immunomodulators such as b‐glucans and bacterial products in an infection are mainly a result of their stimulatory effects on macrophages (Johnston 1978; Chung & Secombes 1988; Júrgensen, Lunde & Robertsen 1993).

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