Rainbow trout samples collected from Lees Ferry this past fall have recently tested negative for whirling disease by the Washington Animal Disease Diagnostic Laboratory in Pullman, Wash.

However, said Arizona Game and Fish Department biologists, last spring some trout sampled at Lees Ferry had tested positive for whirling disease. There are several possible explanations for these two results.

“The most likely explanation is that either whirling disease is present in the population at a very low incidence, and therefore occurrence in our samples is rare, or Lees Ferry trout were exposed to whirling disease, but the disease did not establish,” said Fisheries Branch Chief Kirk Young.

Young said time will tell whether whirling disease is permanently present and if it represents a threat to trout at Lees Ferry. “Certainly the October sampling results are promising. We will continue monitoring fish for possible whirling disease infection and conducting outreach efforts to anglers at the Ferry.”

Meanwhile, Young said, it’s crucial for anglers and others to continue treating Lees Ferry as being positive for whirling disease so that this debilitating trout disease is not spread to other fisheries. Lees Ferry is the only water in Arizona suspected of harboring the microscopic parasite that causes whirling disease.

Whirling disease affects fish in the trout and salmon family. By damaging cartilage, whirling disease can kill young fish directly, or cause infected fish to swim in an uncontrolled whirling motion. This can make it impossible for them to escape predators or to effectively seek food. Whirling disease has no known human health effects.

Wildlife officials are asking anglers to continue taking the following steps at Lees Ferry to prevent the possible spread of the disease to other trout waters:

* Never transport live fish from one water body to another (this is illegal in Arizona).
* Dispose of fish entrails and skeletal parts properly. Never discard fish parts in or near streams or rivers. Do not discard fish parts in a kitchen disposal. Whirling disease spores can survive most wastewater treatment systems. Instead, discard in dry waste that would go to a landfill.
* Rinse all mud and debris from equipment and wading gear, and drain water from boats before leaving an infected drainage.
* Saturate waders and other gear with full-strength Commercial Solutions Formula 409® cleaner degreaser disinfectant or Formula 409® all-purpose cleaner antibacterial kitchen lemon fresh for at least 10 minutes, which is good practice for preventing transfer of other aquatic hitchhikers as well.

Temporary boot cleaning stations are available at the three lodges in the Lees Ferry area, and anglers are encouraged to use them. The National Park Service is also working on plans for more extensive equipment cleaning facilities at Lees Ferry.

Anglers interested in ways to best treat their equipment should visit http://www.whirling-disease.org/files/wd_prevention.pdf for more tips.

Whirling disease is caused by a microscopic parasite called Myxobolus cerebralis. The parasite was introduced to the United States from Europe in the 1950s and has spread to many streams across the United States. The whirling disease parasite has been found in wild fish and fish hatcheries in 25 states. Once established in a stream, the whirling disease parasite cannot be eradicated, nor can its worm host, without significantly damaging the ecosystem.

More information on the disease can be obtained from the Whirling Disease Foundation http://www.tu.org/site/c.kkLRJ7MSKtH/b.3596607/ or at the Whirling Disease Initiative home page. http://whirlingdisease.montana.edu/.