Manifestations of systemic autoimmunity in vaccinated salmon

The development of systemic autoimmunity may result as an undesired side-effect following vaccination, and this condition was recently shown to occur in farmed salmon (Salmo salar). Several of previously reported side-effects following vaccination of fish should therefore be reviewed in the light of this condition. Here, organs and pathological changes in three separate groups of fish severely affected by vaccination were investigated by different morphological methods (n = 84). Granulomas or microgranulomas were observed at the injection site and in several organs. Mott cells were observed in all tissues examined. Pannus-like changes with lymphocyte infiltrates were observed in spines. In conclusion, the reactions following vaccination were of a systemic nature that may be explained by a pathogenetic mechanism caused by systemic autoimmunity.