Original: It was first described from rainbow trout in Germany a century ago , but its range has spread and it has appeared in most of Europe ( including Russia ) , the United States , South AfricaBartholomew , J.L. and Reno , P.W. (/O2002/O) .
Simplified: Myxobolus cerebralis is a small creature that eats the insides of fish like salmon and trout , causing whirling disease .