Development of Bacteria in Fish and in Water During a Standardized Experimental Infection of Rainbow Trout (Salmo gairdneri) with Aeromonas salmonicida

Abstract

In the opinion of many workers, one of the major difficulties in studying furunculosis of salmonids has been the experimental reproduction of the disease (Amend, 1969; Anderson, 1972). Notwithstanding some success obtained with parenteral injection of low doses of the responsible agent, Aeromonas salmonicida (Groberg et al., 1978), this problem has never been well solved. We recently described a standardized method using intramuscular injection of highly virulent bacteria to rainbow trout (Salmo gairdneri), which has given consistent results and has proven fairly reliable in testing the efficacy of therapeutic treatments (submitted for publication). The difficulties that we had to overcome during this work and the proposed solutions are summarized in Table 1. In the present work we have tried to give some additional features of this model, concerning the fate of the causative organism, both when it multiplies in the fish and when it is shed in water by infected fish. Especially in the latter case, serious hazards of superinfections could have interfered with standardization procedure.