I recently read that the release of fish with whirling disease by the state hatcheries was done as a step to introduce more genetic diversity into the wild trout stocks. The fish that were released did have the disease but seemed to tolerate WD well. As an example they cited the fact that the more diverse california rainbows are not affected by WD as hard as their eastern cousins. I cannot help but think of the cane toads that were introduced to australia to help control the cane beetle. The idea seemed good except the only problem was that the beetle lives in the top of the cane where the toads cannot reach them and the toads, which have no natural predators, have overrun many areas.