Evaluation of a Management Strategy to Control the Spread of Myxobolus cerebralis in a Lower Columbia River Tributary

Abstract

In October 2001, Myxobolus cerebralis, the myxozoan parasite that causes salmonid whirling disease, was detected in juvenile rainbow trout Oncorhynchus mykiss from a private hatchery that received water from Clear Creek, a tributary of the Clackamas River, Oregon. The Oregon Department of Fish and Wildlife closed the surface water portion of the hatchery in March 2003 and initiated a monitoring program to evaluate the success of the closure in containing further parasite spread. From 2002 to 2005, rainbow trout sentinels were held in live cages for 2 weeks at locations upstream, downstream, and within the area of the facility and then were tested for M. cerebralis infection. Infection prevalence in groups held in the hatchery pond, the outflow, and downstream of the facility was initially high; however, by May 2004 infection was no longer detected in Clear Creek, although the parasite continued to be detected in the hatchery pond. A single rainbow trout collected approximately 18 river kilometers upstream of the facility in 2002 was infected with M. cerebralis. The parasite was not detected in fish collected from other portions of the Clackamas River drainage, indicating that the introduction was limited. Tubifex tubifex, the invertebrate host for the parasite, were abundant in the hatchery ponds, but only a single specimen was identified in the main stem of Clear Creek. Actinospores of M. cerebralis were only detected in the hatchery waters. The monitoring indicated that the parasite had not become widely established in Clear Creek and that partial closure of the hatchery removed the primary source of infection for fish.

Tubifex Tubifex From Alaska and Their Susceptibility to Myxobolus Cerebralis

“…Because our methods of detection have proven effective in other parts of Alaska (south-central) as well as in other studies (Arsan, 2006;Bartholomew et al, 2007), we think this study accurately represents the relative abundance of T. tubifex in the areas sampled. It is possible that more extensive surveys may detect T. tubifex in southeastern Alaska.…”

“…In reference to the dense populations of worms frequently found where organic enrichment is high, the term sludge worms is often used to describe T. tubifex. Researchers have found the worms in hatchery settling ponds but not in the surrounding stream sediments (Allen and Bergersen, 2002;Bartholomew et al, 2007). Fish hatchery worms were tallied separately in this study (Table II), because settling ponds are independent from the main creek channel, and they are not representative of T. tubifex abundance in the wild.…”

Propagation of the myxozoan parasite Myxobolus cerebralis by different geographic and genetic populations of Tubifex tubifex: An Oregon perspective

“…Furthermore, because of their relatively high worm densities, disturbed environments are more likely to have worm populations at risk of infection. For example, Bartholomew et al (2007) identified a hatchery with a large worm population that propagated M. cerebralis, compared with the adjoining creek with few T. tubifex and no detectable parasite.…”

“…Establishment of the parasite life cycle in tributaries of the lower Columbia River (the Deschutes and Willamette River basins) has occurred only sporadically, after introduction by infected adult salmonids that stray during their return to the upper Columbia River tributaries (Bartholomew and Reno, 2002;Engelking, 2002;Bartholomew et al, 2007;Zielinski, 2008). In the Deschutes River basin, M. cerebralis was detected in 1987 in stray steelhead trout at Warm Springs National Fish Hatchery and later in stray steelhead and Chinook salmon at Round Butte Hatchery (Engelking, 2002).…”

“…In the Willamette River basin, M. cerebralis infection was detected in 2001 in rainbow trout at a private hatchery on Clear Creek, a tributary of the Clackamas River. Closure of this facility in 2003 apparently curtailed the parasite's life cycle and M. cerebralis has not been detected elsewhere in the basin (Bartholomew et al, 2007;Arsan and Bartholomew, 2009).…”