Gills of steelhead trout (Oncorhynchus mykiss) held in liveboxes to detect the presence of pathogens in the Willamette River (Oregon, USA) became heavily infected with trematode metacercariae. The metacercariae encysted adjacent to the cartilaginous rods of gill filaments and elicited a host response of cartilage proliferation from the perichondrium. Although some hyperplasia of gill epithelium and fusion of lamellae was apparent, the extent of damage to the respiratory surface was apparently insufficient to cause trout mortality. Morphological characteristics of the metacercariae did not allow precise identification, but they suggested affinities to either the Heterophyidae or Cryptogonimidae. Some heterophyids are known to cause proliferation of cartilage in fish gills, while cryptogonimids are not. This is the first report of trematode induced gill cartilage proliferation in steelhead trout.
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1 October 1997
A Trematode Metacercaria Causing Gill Cartilage Proliferation in Steelhead Trout from Oregon
Robert E. Olson,
Jack R. Pierce
Journal of Wildlife Diseases
Vol. 33 • No. 4
October 1997
Vol. 33 • No. 4
October 1997
gill cartilage proliferation
metacercaria
Oncorhynchus mykiss
pathology
steelhead trout