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Distribution and transmission of the highly pathogenic parasite Ichthyophonus in marine fishes of Alaska

By: , , , , , and 

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Abstract

A combination of field surveys, molecular typing, and laboratory experiments were used to improve our understanding of the distribution and transmission mechanisms of fish parasites in the genus Ichthyophonus. Ichthyophonus spp. infections were detected from the Bering Sea to the coast of Oregon in 10 of 13 host species surveyed. Sequences of rDNA extracted from these isolates indicate that a ubiquitous Ichthyophonus type occurs in the NE Pacific Ocean and Bering Sea and accounts for nearly all the infections encountered. Among NE Pacific isolates, only parasites from yellowtail rockfish and Puget Sound rockfish varied at the DNA locus examined. These data suggest that a single source population of these parasites is available to fishes in diverse niches across a wide geographic range. A direct life cycle within a common forage species could account for the relatively low parasite diversity we encountered. In the laboratory we tested the hypothesis that waterborne transmission occurs among Pacific herring, a common NE Pacific forage species. No horizontal transmission occurred during a four-month cohabitation experiment involving infected herring and conspecific sentinels. The complete life cycle of Ichthyophonus spp. is not known, but these results suggest that system-wide processes maintain a relatively homogenous parasite population.

Suggested Citation

Gregg, J., Grady, C.A., Thompson, R.L., Purcell, M., Friedman, C., Hershberger, P., 2014, Distribution and transmission of the highly pathogenic parasite Ichthyophonus in marine fishes of Alaska, 46 p.

Publication type Report
Publication Subtype Organization Series
Title Distribution and transmission of the highly pathogenic parasite Ichthyophonus in marine fishes of Alaska
Year Published 2014
Language English
Publisher North Pacific Research Board
Contributing office(s) Western Fisheries Research Center
Description 46 p.
Additional publication details