The Oral Immunization of Trout Against Bacterium Salmonicida

Summary Prolonged feeding of a Bacterium salmonicida vaccine to groups of cutthroat trout, at temperatures varying between 2.2 C and 14.4 C, resulted in: (a) a mortality of the order of 25 per cent in vaccinated trout, compared to a mortality of the order of 75 per cent in untreated fish, when infection was attained by adding a suspension of the virulent organism to the tank water, at 19 C; (b) a marked increase, in the vaccinated groups, in the numbers of fish showing specific agglutinins, and a tendency in this group toward higher agglutinin-titres. A lesser increase in survival-numbers following the same treatment occurred where trout were infected by intramuscular inoculation.