scholarly journals Whirling disease in the Crowsnest River: an emerging threat to wild salmonids in Alberta

2021 ◽  
pp. 1-14
Author(s):  
Clayton T. James ◽  
Marie F. Veillard ◽  
Amanda M. Martens ◽  
Emmanuel A. Pila ◽  
Alyssa Turnbull ◽  
...  
Keyword(s):  
Clinical Signs ◽  
Fish Populations ◽  
Tubifex Tubifex ◽  
Weight Of Evidence ◽  
Whirling Disease ◽  
Myxobolus Cerebralis ◽  
Parasite Life Cycle ◽  
Life Cycle Stages ◽  
Water Fish ◽  
Study Sites

We provide the first documented case of whirling disease (WD) impacts to wild, self-sustaining rainbow trout (RNTR, Oncorynchus mykiss) populations in Canada. Myxobolus cerebralis (Mc), the causative agent of WD, was first confirmed in Alberta in 2016. However, evidence of disease in local fish populations was unknown. Using a weight-of-evidence approach, we examined multiple parasite life cycle stages in the Crowsnest River, Alberta. Percentage of infected Tubifex tubifex worms actively shedding triactinomyxons (TAMs) exceeded known thresholds of Mc establishment and TAM densities instream exceeded thresholds known to cause ≥90% declines in RNTR populations. Mc was detected at 5 of 6 study sites in water, fish, and worms. Disease severity was highest in the lower watershed where 100% of sentinel fish tested positive for Mc 7 to 14 days post-exposure; up to 85% of wild fingerling RNTR showed clinical signs of disease and yearling trout were largely absent from the river suggesting reduced survival. Our findings indicate conditions necessary for outbreak of WD exist in Alberta, highlighting the need to consider this disease as an emerging threat to wild salmonid populations.

Whirling Disease: Reviews and Current Topics

2002 ◽  
Keyword(s):  
River Basin ◽  
Columbia River ◽  
Fish Populations ◽  
Steelhead Trout ◽  
Adult Fish ◽  
Whirling Disease ◽  
Myxobolus Cerebralis ◽  
Hydroelectric Project ◽  
Natural Production ◽  
Deschutes River

<EM>ABSTRACT. </EM>Anadromous fish were excluded above Pelton Round Butte Hydroelectric Project (PRB Project), located midway (RM 100) on the Deschutes River in central Oregon, beginning in 1968. Reintroduction of these fish above the PRB Project is proposed to meet conservation concerns that arise from lack of natural production and separation of populations. One consideration, when moving fish groups that have been isolated one from the other for thirty years, is that of disease. The health of the fish populations above Round Butte Dam could be seriously jeopardized by the introduction of whirling disease. Straying hatchery steelhead trout <em>Oncorhynchus mykiss </em>were detected with <em>Myxobolus cerebralis </em>spores, in 1987, at Warm Springs National Fish Hatchery, below the PRB Project. <em>Myxobolus cerebralis </em>is established in tributaries of the upper Columbia River basin and of the Snake River basin, where some of these straying hatchery and wild steelhead trout may have originated. From 1997 to 2000, fish from the Deschutes River basin have been sampled for the presence of <em>M. cerebralis</em>. The parasite has been found in both straying hatchery and unmarked adult chinook salmon <em>O. tshawytscha </em>and steelhead trout. Presently there is no evidence of infection of resident fish or in returning adult fish originating from Round Butte Hatchery, although the potential for establishment of <em>M. cerebralis </em>in the Deschutes River watershed cannot be ruled out.

Propagated Fish in Resource Management

2004 ◽  
Keyword(s):  
Rainbow Trout ◽  
Infectious Hematopoietic Necrosis Virus ◽  
Fish Populations ◽  
Whirling Disease ◽  
Yersinia Ruckeri ◽  
Myxobolus Cerebralis ◽  
Infectious Hematopoietic Necrosis ◽  
Tetracapsuloides Bryosalmonae ◽  
Parasite Challenge

<em>Abstract.</em>—Laboratory challenges of two rainbow trout <em>Oncorhynchus mykiss </em>strains with <em>Myxobolus cerebralis </em>triactinomyxons confirm the resistance to whirling disease of the Hofer trout strain. Although the number of fish that became infected and developed clinical disease was similar for the Hofer and the Trout Lodge strains at all challenge doses, the median spore numbers were lower at all challenge doses for the Hofer rainbow trout. Parasite challenge doses required to produce lesions of high severity were 10-fold lower for the Trout Lodge strain (100 triactinomyxons) than the Hofer strain (1,000 triactinomyxons). Challenges of the Hofer strain with other common salmonid pathogens; the myxozoans <em>Ceratomyxa shasta </em>and <em>Tetracapsuloides bryosalmonae</em>, the bacterium <em>Yersinia ruckeri</em>, and the viruses Salmonid herpes-like virus type 1 and infectious hematopoietic necrosis virus demonstrate that the susceptibility of the Hofer strain was similar to what would be expected for other strains of rainbow trout, either domestic or wild. These pathogen challenges provide evidence that the Hofer trout present a low risk for introducing any pathogen that might be detrimental to native or established fish populations or further amplifying those that are endemic.

Whirling Disease: Reviews and Current Topics

2002 ◽  
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Positive Control ◽  
Negative Control ◽  
Infected Fish ◽  
Tubifex Tubifex ◽  
Potential Contribution ◽  
Whirling Disease ◽  
Myxobolus Cerebralis ◽  
Dead Fish

<em>ABSTRACT. </em>In Colorado, Windy Gap Reservoir is a focus of <em>Myxobolus cerebralis </em>infectivity of greater intensity than may be explained by the potential contribution of <em>M. cerebralis </em>myxospores by dead fish. One mechanism that would help explain this situation is the expulsion of viable <em>M. cerebralis </em>myxospores by living infected fish. We conducted laboratory experiments to see if <em>Tubifex tubifex</em>, purged of infection by incubation at 26°C for a minimum of 30 d, could become reinfected by exposure to feces and wastes from aquaria containing <em>M. cerebralis</em>-infected brown trout <em>Salmo trutta</em>. In two separate experiments, replicate experimental units of <em>T. tubifex </em>were thoroughly infected in this manner. By comparison, evidence of infection in negative control replicates was much weaker in both experiments. It is possible that the purging process used to remove initial infection was not 100% effective, yet the differences between experimental and negative control replicates were dramatic. Positive control replicates, intentionally exposed to harvested myxospores of <em>M. cerebralis</em>, became heavily infected in both experiments. These results strongly support the hypothesis that brown trout are capable of expelling viable <em>M. cerebralis </em>myxospores.

Myxobolus cerebralis (Myxozoa), the causative agent of whirling disease, reduces fecundity and feeding activity of Tubifex tubifex (Oligochaeta)

Parasitology ◽  
2009 ◽  
Vol 136 (6) ◽  
pp. 603-613 ◽  
Author(s):  
S. SHIRAKASHI ◽  
M. EL-MATBOULI
Keyword(s):  
Causative Agent ◽  
Feeding Activity ◽  
Ecological Impacts ◽  
Tubifex Tubifex ◽  
Infection Prevalence ◽  
Limited Information ◽  
Whirling Disease ◽  
Myxobolus Cerebralis ◽  
Cocoon Production ◽  
Spore Release

SUMMARYMyxobolus cerebralis is the causative agent of whirling disease that has significant economical and ecological impacts on trout populations. Although intensive studies have been conducted to understand its effects on and interactions with its fish host, only limited information is available about how and to what extent M. cerebralis affects its oligochaete host, Tubifex tubifex. We investigated the effects of M. cerebralis on survival, growth, reproduction, and feeding activity of T. tubifex. Mature, immature and juvenile worms were exposed to myxospores and their infection prevalence, mortality, sexual development, reproduction and spore production were compared with unexposed worms. The parasite affected neither survival nor growth but inhibited clitellar development and reduced cocoon production by over 80%. Numbers of actinospores released from mature worms were nearly 9-fold higher than that of immature worms. When non-clitellated infected worms were kept at 30°C for 4 days, spore release ceased and they re-developed a clitellum. These results suggest parasite-induced castration. Comparative monitoring of defecation rate revealed that M. cerebralis reduced feeding activity of T. tubifex by approximately 40%. Low energy intake and impaired energetic allocation may be the underlying mechanism behind reduced fecundity of infected T. tubifex.

Whirling Disease: Reviews and Current Topics

2002 ◽  
Keyword(s):  
Clinical Signs ◽  
Cutthroat Trout ◽  
The Other ◽  
Mountain Streams ◽  
Oncorhynchus Clarki ◽  
Whirling Disease ◽  
Myxobolus Cerebralis ◽  
Histological Evidence ◽  
Spawning Sites

<EM>ABSTRACT. </EM>We assessed endemic age-0 cutthroat trout <em>Oncorhynchus clarki </em>for evidence of pathology associated with <em>Myxobolus cerebralis </em>in two streams formed by springs in western Wyoming. We hypothesized that the location of spawning sites in spring streams would affect the extent of exposure of cutthroat trout fry to <em>M. cerebralis </em>triactinomyxons (tams), occurrence of the parasite in their bodies, and clinical signs of whirling disease. The spring streams were warm relative to nearby streams flowing from the mountains or spawning and emergence of fry was early compared with fish in mountain streams. Tams were abundant early in the summer and clinical signs of whirling disease among age-0 fish were seen as early as mid-June in one stream. There were high densities of tams in one stream, and densities declined with upstream progression from May through July, whereas in the other stream, low densities of tams were observed in the downstream portion early in the summer, and they were not detected in July and August. Age-0 cutthroat trout were abundant; clinical signs of whirling disease were evident, and histological evidence of whirling disease was common in the stream where tams were abundant. Low densities of age-0 cutthroat trout and no clinical signs of whirling disease were observed in the stream where tams were not abundant. Among sentinel fish in the stream with abundant tams, we found extensive occurrence of <em>M. cerebralis</em>, with many fish showing clinical signs and histological evidence of pathology associated with <em>M. cerebralis</em>. The proportion of sentinel fish with clinical and histological signs of whirling disease decreased with upstream progression. In the stream with low tam, densities sentinel fish became infected with <em>M. cerebralis</em>, but there were essentially no clinical signs or histological indications of whirling disease.

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