Agent for whirling disease found in trout in five northeast Washington waters

Federal and state fish scientists have found the pathogen that causes whirling disease in trout in five locations in northeast Washington.

Although harmless to humans and other wildlife, whirling disease has been blamed for significant declines in trout populations in Montana and Colorado.

Fish pathologists from the U.S. Fish and Wildlife Service (USFWS) and the Washington Department of Fish and Wildlife (WDFW) found the pathogens during an on-going wild fish health survey in Pend Oreille, Stevens and Ferry county streams. Although not the first time the whirling disease agent has been found in Washington, this is the furthest upstream occurrence in the Columbia River drainage.

Waters where the pathogen was detected are: Scatter Creek (Ferry County); Cee Cee Ah Creek, the east branch of Le Clerc Creek, and the north fork of Calispell Creek (all in Pend Oreille County), and the south fork of Mill Creek (in Stevens County).

Although the disease-causing pathogen was detected, the disease itself was not. The presence of the pathogen was confirmed at only five locations, out of a total of 60 sites sampled. All the fish in which the pathogen were found were eastern brook trout.

Field sampling in the area occured in late summer when the sites were accessible. The samples were sent to the U.S. Fish and Wildlife Service's Idaho Fish Health Center for analysis.

The new detection significantly expands the known geographic range of the pathogen, said WDFW Fish Health Program Manager John Kerwin.

"This will definitely affect how we handle fish from those areas," he said.

Kerwin said fisheries managers from several agencies and organizations will work cooperatively on a plan to prevent the spread of the pathogen and further investigate its presence during the 2002 field season.

Whirling disease is a parasitic infection of salmon and trout caused by the microscopic protozoan, Myxobolus cerebralis. The disease causes deformity and death in some species of trout while other related species, notably salmon and char, seem unaffected. Some of the deformities in affected fish cause them to "whirl" in a tail-chasing pattern.

The disease is not passed directly from fish to fish but through an intermediate aquatic host, tubifex worms. The pathogen passes through the worm, changing into an infectious form, before being released back into the water where it can infect fish and cause the disease. If a fish eats the host worm, spores of the pathogen infect the fish and cause the disease. When the fish dies, spores of the pathogen are released, find the intermediate host, and the cycle begins again. Tubifex worms are found throughout North America, including the state of Washington.