Effect of Renibacterium salmoninarum levels in the ovarian fluid of spawning Chinook salmon on the prevalence of the pathogen in their eggs and progeny

Abstract

Chinook salmon, Oncorhynchus tshawytscha , eggs were exposed to ovarian fluid inoculated with various concentrations of Renibacterium salmoninarum (Rs), the causative agent of bacterial kidney disease of salmonids. Intraovum infections occurred in eggs exposed to Rs cells at concentrations of 1.7 x 10 super(5) or higher/ml. Smolts derived from these eggs were Rs-infected. As with eggs, the highest prevalence of infection in smolts occurred in those derived from eggs exposed to the highest concentration of Rs tested. In addition, smolts derived from eggs that were not deliberately exposed to Rs, but which were obtained from ovarian fluid naturally infected with as few as 28 to 113 Rs cells/ml, were also infected.