RELEVANCE OF RENIBACTERIUM-SALMONINARUM IN AN ASYMPTOMATIC CARRIER POPULATION OF BROOK TROUT, SALVELINUS-FONTINALIS (MITCHILL)

These studies were done to determine the prevalence of infection, over time, of progeny from a population of 1988 year class brook trout, Sa lvelinus fontinalis (Mitchill), that was asymptomatically infected wit h Renibacterium salmoninarum, the causative agent of bacterial kidney disease. This population and its progeny from the 1991 and 1992 spawni ngs were monitored for approximately 3 years for prevalence of R. salm oninarum and development of bacterial kidney disease. Ovarian fluid sa mples from the 1991 and 1992 spawnings, and from a 1993 spawning of th e 1991 progeny, were analysed for R. salmoninarum by enzyme linked imm unosorbent assay (ELISA) and the membrane filtration fluorescent antib ody technique. Kidney and spleen tissues of the 1988 year class were a ssayed by ELISA following the 1992 spawning. The progeny of the 1991 a nd 1992 spawnings were followed for increased prevalence of R. salmoni narum by the ELISA. Kidney tissues were assayed and sampling began onc e the fish were large enough. Each population of progeny was sampled q uarterly for one year. Overall, the progeny displayed decreasing preva lence of R. salmoninarum and all ovarian fluids of the 1991 progeny (i n 1993) were negative. Brood fish and progeny remained asymptomatic du ring the course of the study.