Comparative susceptibility of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta to Myxobolus cerebralis, the cause of salmonid whirling disease

Ronald Hedrick, Terry S. McDowell, Melanie Gay, Gary D. Marty, Marios P. Georgiadis, Elizabeth MacConnell

Research output: Contribution to journalArticle

93 Citations (Scopus)

Abstract

The susceptibility of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta to Myxobolus cerebralis, the cause of salmonid whirling disease, was assessed following dosed exposures to the infectious stages (triactinomyxons). Parallel groups of age-matched brown trout and rainbow trout were exposed to 10, 100, 1000 or 10 000 triactinomyxons per fish for 2 h and then placed in aquaria receiving single pass 15°C well water. Severity of infection was evaluated by presence of clinical signs (whirling and/or black tail), prevalence of infection, severity of microscopic lesions, and spore counts 5 mo after exposure. Clinical signs of whirling disease, including a darkened caudal region (black tail) and radical tail chasing swimming (whirling), occurred first among rainbow trout at the highest dose at 6 to 7 wk post exposure. Black tail and whirling occurred among rainbow trout receiving 1000 and 100 triactinomyxons per fish at 8 to 9 wk post exposure. Only 1 of 20 fish had a black tail among rainbow trout receiving 10 triactinomyxons per fish, although 30 % of the fish were infected at 5 mo post exposure. Black tails were observed in brown trout at 1000 and 10 000 triactinomyxons per fish beginning at 11 and 7 wk post exposure, respectively. There was no evidence of the tail chasing swimming (whirling) in any group of brown trout. The prevalence of infection, spore numbers, and severity of microscopic lesions due to M. cerebralis among brown trout were less at each exposure dose when compared to rainbow trout. Infections were found among rainbow trout at all doses of exposure but only among brown trout exposed to doses of 100 triactinomyxons per fish or greater. Risk of infection analyses showed that rainbow trout were more apt to be infected at each exposure dose than brown trout. Spore counts reached 1.7 x 106 per head among rainbow trout at the highest dose of exposure compared to 1.7 x 104 at the same exposure dose among brown trout. Spore numbers increased with dose of exposure in rainbow trout but not in brown trout. As microscopic lesion scores increased from mild to moderate, spore numbers increased in rainbow trout but not brown trout. The mechanisms by which brown trout resist infections with M. cerebralis were not determined. Cellular immune functions, including those of eosinophilic granular leukocytes that were more prominent in brown trout than rainbow trout, may be involved.

Original languageEnglish (US)
Pages (from-to)173-183
Number of pages11
JournalDiseases of Aquatic Organisms
Volume37
Issue number3
DOIs
StatePublished - Sep 14 1999

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whirling disease
Myxobolus cerebralis
salmonid
Salmo trutta
rainbow
Oncorhynchus mykiss
tail
spore
dosage
fish
spores
lesion
lesions (animal)
infection
exposure
dose
aquarium
well water
aquariums

Keywords

  • Brown trout
  • Myxobolus cerebralis
  • Myxozoan
  • Whirling disease

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science

Cite this

Comparative susceptibility of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta to Myxobolus cerebralis, the cause of salmonid whirling disease. / Hedrick, Ronald; McDowell, Terry S.; Gay, Melanie; Marty, Gary D.; Georgiadis, Marios P.; MacConnell, Elizabeth.

In: Diseases of Aquatic Organisms, Vol. 37, No. 3, 14.09.1999, p. 173-183.

Research output: Contribution to journalArticle

Hedrick, Ronald ; McDowell, Terry S. ; Gay, Melanie ; Marty, Gary D. ; Georgiadis, Marios P. ; MacConnell, Elizabeth. / Comparative susceptibility of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta to Myxobolus cerebralis, the cause of salmonid whirling disease. In: Diseases of Aquatic Organisms. 1999 ; Vol. 37, No. 3. pp. 173-183.
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