Research by OSU scientists, including Dr. Jerri Bartholomew, on the C.  shasta parasite’s role in the Klamath Basin began in the early 1980s in the Williamson and Lower Sprague Rivers, where high populations of worms were detected on the riverbed and high densities of parasite spores in the water. But the disease only seemed to impact non-native rainbow trout, which had been transplanted from another system and, unlike the native trout, hadn’t developed a resistance to C. shasta.