(Salem, OR) -- A new parasite is sickening rainbow trout raised at three Oregon fish hatcheries. ODFW fish health and hatchery staff noticed more fish dying at the Klamath Falls, Rock Creek and Elk River facilities, but they didn't detect any known pathogens in subsequent testing. Oregon State University's College of Veterinary Medicine and Department of Microbiology were brought in to help. They discovered a previously unknown parasite infecting blood vessels, gills and kidney tissue of the trout. It appears to first infect invertebrates like worms, then move into the water, where it infects fish. To stop the spread, ODFW disposed of 160-thousand legal-sized rainbow trout, which will lead to a slight decline in the number of trout stocked across the state.