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We used a simple technique for filtering the actinospores of Myxobolus cerebralis from natural waters to observe seasonal periodicity at eight sites in the upper Colorado River drainage. We used a tub lined with 20-?m-mesh Pecap screen to concentrate actinospores from 1,900-L samples and estimate density by microscope count. Identity of the observed actinospores as those of M. cerebralis was confirmed in 86 samples by the use of a polymerase chain reaction test. The 42-ha Windy Gap Reservoir appeared to be a point source of actinospores; the highest densities observed were consistently from samples taken at sites just below the reservoir. Both densities and the frequency of detection were much lower 26 km below...
We chose a hypolimnetic-release tailwater of the San Juan River, New Mexico, to characterize the etiology of whirling disease, a parasitic infection of salmonids. We sampled a 2-km reach of the tailwater in August and December 2001 and June 2002 to characterize environmental factors influencing the distribution and density of Tubifex tubifex lineages and Myxobolus cerebralis infection rates. Shortly after the scouring flow, organic matter in sediments and T. tubifex densities increased within deep habitats. In contrast, no differences were observed in T. tubifex densities and organic matter collected from shallow habitats throughout the three sampling dates. Within this study area, we found three sympatric lineages...
We chose a hypolimnetic-release tailwater of the San Juan River, New Mexico, to characterize the etiology of whirling disease, a parasitic infection of salmonids. We sampled a 2-km reach of the tailwater in August and December 2001 and June 2002 to characterize environmental factors influencing the distribution and density of Tubifex tubifex lineages and Myxobolus cerebralis infection rates. Shortly after the scouring flow, organic matter in sediments and T. tubifex densities increased within deep habitats. In contrast, no differences were observed in T. tubifex densities and organic matter collected from shallow habitats throughout the three sampling dates. Within this study area, we found three sympatric lineages...
Two sizes of fingerling Snake River cutthroat trout Oncorhynchus clarkii behnkei and Colorado River rainbow trout O. mykiss were raised at hatcheries testing negative for Myxobolus cerebralis and stocked into the Dolores and Cache la Poudre rivers from 1999 to 2001. Populations were resampled over a 2-year period to determine which species and size combination had the highest growth and survival rates. Fish were tested for M. cerebralis via polymerase chain reaction and pepsin?trypsin digest analyses. Growth and survival rates between the species and size groups were not significantly different in either river. In the Dolores River, annual survival for both species and sizes of fish combined ranged from 0.063 to...
We compared the resistance to whirling disease of two groups of Colorado River rainbow trout Oncorhynchus mykiss and a domestic strain of rainbow trout in a controlled laboratory challenge. These three groups represented the progeny of wild rainbow trout known to have recruited (1) during the early years of infestation by Myxobolus cerebralis of the Colorado River or (2) before the presence of M. cerebralis in the system and (3) the Erwin strain of rainbow trout. The severity of whirling disease in each group was dependent on the dose of triactinomyxons of M. cerebralis to which the fish were exposed. Microscopic lesions and spore counts both increased with increasing parasite dose. Survival of the progeny of Colorado...
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