Effects of fish age and parasite dose on the development of whirling disease in rainbow trout

Diseases of Aquatic Organisms

Alexander V. Zale¹  Eileen K. N. Ryce¹  Elizabeth MacConnell¹ 

关键词: Myxobolus cerebralis;    Whirling disease;    Resistance;    Age;    Dose;    Rainbow trout;   

DOI  :  10.3354/dao059225

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: We determined the ages at which juvenile rainbow trout Oncorhynchus mykiss became resistant to the effects of whirling disease following exposure to a range of parasite doses. Heretofore, the development and severity of whirling diseasein salmonids was known to be generally dependent on the age or size of fish when first exposed to the triactinomyxon spores of Myxobolus cerebralis; larger, older individuals tended to be less diseased. However, no systematic determination had beenmade of the exact age at which fish become resistant to the development of the disease. We exposed rainbow trout at 9 ages (1 to 17 wk post-hatch) to 4 parasite dose levels (0, 100, 1000 and 10000 triactinomyxons per fish). Disease severity was measuredusing mortality, clinical signs, microscopic pathology, and myxospore counts. Disease and mortality were substantially reduced when exposure to the parasite occurred for the first time at 9 wk post-hatch (756 degree-days at 12°C) or older. High doseselicited more disease among the younger age groups, but the effect was dampened in groups exposed at about 9 to 11 wk post-hatch and absent thereafter. Rainbow trout reared in M. cerebralis-free waters for 9 wk post-hatch or longer, whether in thewild or in a hatchery situation, should experience greater survival and less disease than fish first exposed to the parasite at younger ages.

【 授权许可】

Unknown