Effect of water temperature on the morbidity of Tetracapsuloides bryosalmonae (Myxozoa) to brown trout (Salmo trutta) under laboratory conditions

Proliferative kidney disease (PKD) is a disease found in salmonid fish that is widespread in Europe and North America. The dependency of the clinical signs on the water temperature is extensively reported in rainbow trout, but detailed information on brown trout is lacking. In this study, juvenile brown trout were exposed to the spores of Tetracapsuloides bryosalmonae and then kept at different ambient water temperatures (16 degrees C, 19 degrees C and 22 degrees C) for 10 weeks along with recording of morbidity throughout the experiment. At 6, 8 and 10 weeks post-exposure, fish from each temperature group were sampled and underwent pathoanatomical examination to survey disease progression. At 16 degrees C, brown trout showed a significantly higher survival probability compared to those kept in 19 degrees C and 22 degrees C water. Additionally, the parasitic burden (MSQ) was higher and the clinical signs were more pronounced in the brown trout kept at 19 degrees C and 22 degrees C compared with the ones kept at 16 degrees C. This study highlights the correlation of PKD outbreaks and water temperature increases related to global climate change, which will impact the future distribution of brown trout in natural waters.

Automated summary

This study found that the survival probability, parasitic burden, and clinical signs of brown trout are influenced differently under different water temperature conditions, with brown trout exposed to lower temperatures showing higher survival probability and less severe disease symptoms.