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: In the last 100 years, it has spread to most of Europe (including Russia), the United States, South Africa, and other countries.