Transcriptome profiling of brown trout posterior kidney during proliferative kidney disease

Tetracapsuloides bryosalmonae is a serious pathogen that causes proliferative kidney disease (PKD) in salmonids. This parasite causes significant economic losses to salmonid aquaculture operations. Moreover, this parasite is attributed to the declining brown trout population in Alpine streams. The parasite proliferates and matures in the kidney of infected brown trout are released via urine into the aquatic environment. It is interesting to note that, the European strain of T. bryosalmonae parasite could persist in the PKD survived brown trout and the fish could release viable parasitic spores even after 5 years. Therefore, information on the host-parasite interaction is crucial to understand the brown trout host response to T. bryosalmonae infection. We employed RNA-seq based transcriptome analysis to decipher brown trout host response during parasite proliferation in the posterior kidney. In our experiment, we exposed specific pathogen free brown trout to T. bryosalmonae and collected posterior kidney samples at various time points post exposure. The posterior kidney samples were examined for proliferating T. bryosalmonae parasitic spores based on immunohistochemistry. We found numerous parasites in the posterior kidney of brown trout at different time points. Six control and six T. bryosalmonae exposed brown trout posterior kidneys were subjected to Illumina RNA sequencing and transcriptomic analysis.