An article came to my attention from the Whirling Disease Foundation. FYI.
Steve Schalla
Whirling Disease Foundation Press Release
In the U.S., although at least 15 different strains of rainbow trout have been tested in an effort to find a strain with resistance to whirling disease, no significant differences in resistance have been apparent. However, in 1999, Dr. El-Matbouli reported that whirling disease was no longer observed in certain hatcheries in Germany. Because these hatcheries had a history of whirling disease problems, he suspected that resistance may have developed as a result of continuous exposure (up to 150 years) to the parasite. If this observation proved to be true, this would be the first evidence that rainbow trout could develop resistance. In February of 2001, the Whirling Disease Foundation was presented with a research proposal from Drs. Hedrick and El-Matbouli. In the first phase of this research, the resistance of the Hofer strain of rainbow trout was demonstrated in controlled laboratory challenges conducted under a variety of conditions. The confirmation of a naturally resistant rainbow trout in Germany offers unprecedented opportunities for long-term solutions to whirling disease in the U.S. The potential outcomes of this research are:
to provide scientists with an essential tool for determining how resistance may develop in our wild and native North American trout
to provide opportunities for re-establishment of certain wild populations of rainbow trout in areas where their numbers have declined drastically and
to provide information for decision making regarding the use of these fish for the purpose of decreasing parasite numbers (e.g. aquaculture, non-salmonid habitats). The Whirling Disease Foundation recognizes that plans to re-introduce/re-establish rainbow trout populations using the Hofer strain must proceed with caution. Foremost, it is necessary to provide assurance that these fish do not pose a threat to existing populations by introducing exotic pathogens and that development of resistance to whirling disease has not occurred at the expense of increased susceptibility to other diseases they might encounter here. These concerns were addressed in the second phase of the research. To date, after repeated health inspections there has been no evidence of exotic pathogens, and no evidence of heightened susceptibility to common diseases. Second are native trout concerns. The most likely role for these fish is in states where rainbow trout are not native, and therefore would not interfere with rainbow trout management programs. Here, the Hofer trout strain should be incorporated into selective breeding programs with established rainbow trout strains having other desired characteristics. The WDF is supporting initial efforts in Colorado to look at the resistance of progeny from crosses between Hofer rainbow trout and other strains (e.g. Harrison Lake). However, as with existing rainbow trout programs, use of these fish should not occur at the expense of re-establishing native fish assemblages, particularly those fish species that might hybridize with rainbow trout (e.g. cutthroat trout).
