Whirling Disease: Reviews and Current Topics

Effects of Myxobolus cerebralis Infection on Juvenile Spring Chinook Salmon in the Lostine River, Oregon

Todd A. Sandell, Harriet V. Lorz, Sarah A. Sollid and Jerri L. Bartholomew

doi: https://doi.org/10.47886/9781888569377.ch13

ABSTRACT. The potential for Myxobolus cerebralis, the cause of salmonid whirling disease, to affect resident populations of spring chinook salmon Oncorhynchus tshawytscha in the Lostine River, Oregon, was investigated in this study. Spring chinook salmon and rainbow trout O. mykiss fry were held in the Lostine River for 14 d in late March 1999, when resident chinook salmon alevins naturally emerge. After exposure, fry were held in pathogen-free water in the laboratory. The prevalence of infection at 5 months postexposure, as determined by PCR, was equivalent in both species (37.5% and 41%, respectively). Only rainbow trout developed cranial lesions (average lesion severity 0.4 on a 5-point scale; 4 of 10 fish examined were positive), and no spores were detected in homogenates of cartilage from fish of either species. Comparison of data on chinook salmon spawning sites (1996–2000) with known distribution of M. cerebralis in the Lostine River demonstrated that the majority of chinook salmon spawn in the middle section of the river, where levels of M. cerebralis exposure were reduced. Results of this study indicate that juvenile chinook salmon may become infected with M. cerebralis, when naturally exposed to the parasite, but suggest that the timing and location of their emergence may mitigate the negative impacts of M. cerebralis infection in this river.