Failure of anti-furunculosis vaccination of rainbow trout (Salmo gairdneri Richardson). Using extra-cellular products of Aeromonas salmonicida as an immunogen.

Furunculosis vaccines were prepared from virulent strains of Aeromonas salmonicida: 2 were formalin killed bacterins, and 3 were “cell surface extracts” prepared by stirring the bacteria in lithium acetate-EDTA buffer at different pH in presence of glass beads. Rainbow trout were vaccinated by intra-peritoneal injection and challenged with virulent strains injected intra-muscularly or added to water. Although the challenges were conducted at the wanted levels and provided good reliability, no protection could be demonstrated in any of the tested groups. Techniques and methods of work cannot explain these failures and it is concluded that rainbow trout were not protected. Discrepances of these results with other recent reports are outlined, and some comments are done about the meaning and bearing of furunculosis vaccination studies.