Antibody Production and Immune Responses of Rainbow Trout and Coho Salmon to Chondrococcus columnaris

Active immunity to Chondrococcus columnaris disease was established in coho salmon (Oncorhynchus kisutch) approximately 3 months old by oral vaccination with heat-killed cells. Average agglutinating titers were 1:17 for control survivors and 1:168 for the orally vaccinated salmon. When rainbow trout (Salmo gairdneri) approximately 3 months old were exposed in a trough to C. columnaris present as a natural contaminant in Columbia River water, 52% of the fish died during the first 6 weeks of the test. Fish that survived the exposure were generally resistant to subsequent challenge. Many age 1 + rainbow trout that survived the C. columnaris infection as juveniles, when sampled after several months of reexposure to the disease, were immune carriers of the pathogen and developed agglutinating antibody titers ranging from 1:80 to 1:640. Titers up to 1:5120 were developed in disease-free yearling rainbow trout by parenteral vaccination.