Chehalis river disease - a unique gill disease of ...
|Title||Chehalis river disease - a unique gill disease of salmonids|
|Author(s)||G. C. Newbound, David J. Speare, K. Larry Hammell, M. L. Kent, V. E. Ostland, G. S. Traxler|
|Journal||Canadian Journal of Fisheries and Aquatic Sciences|
|Abstract||Epidemic mortalities of chinook salmon alevins (Oncorhynchus tshawytscha) have occurred annually at a freshwater hatchery at the Chehalis River, British Columbia, Canada, since 1982. Previous work has identified branchial epithelial hyperplasia as the predominant pathological change. Our initial work lead us to test the hypothesis that Chehalis River disease (CRD) was actually a novel form of bacterial gill disease (BGD). Histological and ultrastructural observations indicated that CRD-affected gills harboured a bacterial biofilm apparently complexed with particulate iron prior to and during clinical CRD. In one instance, extracellular viruslike particles were observed. Large numbers of a mixed bacterial population were recovered from diseased gills. Flavobacterium sp. and Pseudomonas fluorescens were considered the predominant isolates from the 1990-91 outbreak. However, indirect immunofluorescence of gills with anti-Flavobacterium branchophila serum failed to detect antigenically similar bacteria on the gills of CRD-affected fish. Chemotherapeutic treatment of both naturally and experimentally infected fish was successful, thereby confirming the infectious nature of the disease. We conclude that CRD is a form of BGD, but the significance of the branchial viruslike particles and the presence of particulate iron has not yet been established.|
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