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

Diseases of Aquatic Organisms

Terry S. McDowell¹  Melanie Gay¹  Gary D. Marty¹  Marios P. Georgiadis¹  Ronald P. Hedrick¹  Elizabeth MacConnell¹ 

关键词: Myxozoan;    Myxobolus cerebralis;    Whirling disease;    Brown trout;   

DOI  :  10.3354/dao037173

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

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 theinfectious stages (triactinomyxons). Parallel groups of age-matched brown trout and rainbow trout were exposed to 10, 100, 1000 or 10000 triactinomyxons per fish for 2 h and then placed in aquaria receiving single pass 15°C well water. Severity ofinfection 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 wkpost 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 10000 triactinomyxons per fishbeginning 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 x10⁴ 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 butnot 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 thanrainbow trout, may be involved.

【 授权许可】

Unknown