Location: Cool and Cold Water Aquaculture Research
Title: Examination of resistance and tolerance in rainbow trout bred for differential susceptibility to bacterial cold water disease Authors
Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 2013
Publication Date: May 2, 2013
Citation: Marancik, D.P., Leeds, T.D., Blazer, V.S., Wiens, G.D. 2013. Examination of resistance and tolerance in rainbow trout bred for differential susceptibility to bacterial cold water disease. Annual Eastern Fish Health Workshop. 056. Technical Abstract: Animals exhibit two interrelated defense strategies following challenge with a pathogen: resistance and tolerance. Resistance refers to the host's capacity to limit pathogen number while tolerance refers to the ability to limit the negative health impact of a given pathogen load. Resistance and tolerance were examined in rainbow trout selectively bred for increased survival (R-line) and increased susceptibility (S-line) to bacterial cold water disease (BCWD). Rainbow trout were challenged intraperitoneally or subcutaneously with Flavobacterium psychrophilum strain CSF 259-93. Mortality in R-line and S-line fish was recorded over 21 days and systemic bacterial loads were compared using qPCR. Tissue necrosis and inflammation were characterized by histopathology. The R-and S-lines exhibited significantly different survival independent of challenge route. Quantitative PCR results indicate similar initial splenic and renal bacterial loads between lines but significantly lower levels of bacteria in R-line fish by day 6 post-infection, demonstrating that mechanisms of resistance contribute to R-line survival. This suggests that BCWD selective breeding has primarily selected for host resistance. While pathogen loads varied between the two lines, histopathology did not demonstrate appreciable differences in tissue damage in R-line and S-line fish to suggest that decreased lesion development plays a direct role in disease tolerance. Future studies will examine mechanisms of bacterial clearance in R-line fish and explore additional tolerance mechanisms that may contribute to survival.