TEMPERATURE IMPACTS ON ATLANTIC SALMON (SALMO SALAR) RESPONSE TO INFECTION WITH RENIBACTERIUM SALMONINARUM
Mark Fast, University of Prince Edward Island
Jonathon E. Perreira, Sara L. Purcell, and Mark D. Fast.
Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE C1A 4P3, Canada.
Mitigating the impact of climate-related challenges on salmon and understanding how climate factors affect host-pathogen interactions is essential to the future sustainability of salmon aquaculture. Among these challenges, is understanding the mechanisms by which current pathogens, like Renibacterium salmoninarum (Rsal), exploit their hosts, Atlantic salmon (Salmo salar), and under what conditions the host is able to fight off infection and prevent the development of Bacterial Kidney Disease. For most of the year in Eastern North American sea cage culture, temperatures are between 8-13oC, however, IPCC and other future global climate predictions foresee coastal regions experiencing extended periods up to
and beyond 20 oC. For this reason, multiple studies have been initiated to investigate BKD progression and Atlantic salmon immune responses at 13 oC (i.e. current temperature) compared to 20 oC (i.e. future temperature). Following a period of acclimation to these different temperature regimes, salmon smolts (150-300 g) were inoculated (i.p.) with a culture of R. salmoninarum. Over multiple studies, mortalities at 13 oC reached between 50-100%, whereas exposure at 20 oC resulted in 0% mortality. Despite, Rsal growth in culture at 20 oC no clinical signs were observed in salmon exposed at 20 oC, but also showed no significant difference in survival upon re-exposure at 13 oC (ca. 50%), compared to naïve salmon exposed at 13 oC (ca. 50%). Dual transcriptome analysis of head kidneys of exposed Atlantic salmon showed impacts in endo/exocytosis, phagosome, lysosome, MAPK signaling, NOD-like receptor signaling and other pathways associated with intracellular pathogen recognition and processing. Temperature impacts and exposure history will be discussed with respect to antibody production, recognition and intracellular success of Rsal infection in Atlantic salmon.