Study 8: Prevalence and load of Nanophyetus salmincola infection in outmigrating steelhead trout from five Puget Sound rivers

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Abstract

Nanophyetus salmincola is a parasitic trematode, or flatworm, that infects salmonid fishes in the Pacific Northwest, including Washington, Oregon, and portions of California. The adult worm lives in the intestine of fish-eating birds and mammals. Eggs shed into the water hatch into miracidia which penetrate the first intermediate host, one of two species of snail Juga plicifera or J. silicula. Asexual reproduction occurs within the snail. Free-swimming cercaria are released from the snail and penetrate the secondary intermediate host, often a salmonid fish, in fresh and brackish water. The cercaria encyst as metacercaria in various organs of the fish, including gills, muscle and heart, but favor the posterior kidney. Penetration and migration by the cercaria through the fish causes damage to nearly every organ system. Once encysted, metacercaria survive the ocean phase of salmonid life cycle. N. salmincola is a likely contributor to mortality of juvenile coho salmon (Oncorhynchus kisutch) during the early ocean rearing phase, and it is the most prevalent pathogen of outmigrating steelhead in the estuaries of the Pacific Northwest.

A field survey was implemented from March-June 2014 to compare the prevalence and parasite load of N. salmincola infections in outmigrating steelhead from five Puget Sound watersheds and to assess changes in infection levels that occurred during the smolt out-migration through each watershed. N. salmincola infection prevalence and parasite loads were determined by counting metacercaria in posterior kidney samples. Tissue samples were collected and examined by standard histological methods.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Study 8: Prevalence and load of Nanophyetus salmincola infection in outmigrating steelhead trout from five Puget Sound rivers
Year Published 2015
Language English
Publisher Long Live the Kings
Publisher location Seattle, WA
Contributing office(s) Western Fisheries Research Center
Description 2 p.
Larger Work Type Book
Larger Work Subtype Monograph
Larger Work Title Puget Sound steelhead marine survival: 2013-2015 research findings summary
First page 46
Last page 48
Country United States
State Washington
Other Geospatial Puget Sound