Sidebar by Ed Quillen
Whirling Disease – October 1999 – Colorado Central Magazine
Whirling Disease gets its name from its effect on fingerling trout. If they’re infected, they tend to swim in circles, like puppies chasing their tails — except it isn’t cute when trout do it.
WD most often affects trout when they’re young, less than four inches long. It attacks their soft cartilage before it hardens into bone, causing skeletal deformities and nervous-system damage (thus the whirling), and sometimes death.