DAO 99:139-144 (2012)  -  doi:10.3354/dao02458

Inability to demonstrate fish-to-fish transmission of Ichthyophonus from laboratory infected Pacific herring Clupea pallasii to naïve conspecifics

J. L. Gregg1,*, C. A. Grady1, C. S. Friedman2, P. K. Hershberger1

1Marrowstone Marine Field Station, Western Fisheries Research Center, US Geological Survey, 616 Marrowstone Point Road, Nordland, Washington 98358, USA
2School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, Washington 98195, USA

ABSTRACT: The parasite Ichthyophonus is enzootic in many marine fish populations of the northern Atlantic and Pacific Oceans. Forage fishes are a likely source of infection for higher trophic level predators; however, the processes that maintain Ichthyophonus in forage fish populations (primarily clupeids) are not well understood. Lack of an identified intermediate host has led to the convenient hypothesis that the parasite can be maintained within populations of schooling fishes by waterborne fish-to-fish transmission. To test this hypothesis we established Ichthyophonus infections in Age-1 and young-of-the-year (YOY) Pacific herring Clupea pallasii (Valenciennes) via intraperitoneal (IP) injection and cohabitated these donors with naïve conspecifics (sentinels) in the laboratory. IP injections established infection in 75 to 84% of donor herring, and this exposure led to clinical disease and mortality in the YOY cohort. However, after cohabitation for 113 d no infections were detected in naïve sentinels. These data do not preclude the possibility of fish-to-fish transmission, but they do suggest that other transmission processes are necessary to maintain Ichthyophonus in wild Pacific herring populations.


KEY WORDS: Ichthyophonus · Pacific herring · Horizontal transmission · Parasite


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Cite this article as: Gregg JL, Grady CA, Friedman CS, Hershberger PK (2012) Inability to demonstrate fish-to-fish transmission of Ichthyophonus from laboratory infected Pacific herring Clupea pallasii to naïve conspecifics. Dis Aquat Org 99:139-144

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