A Genomics Study of the Role of Infectious Hematopoietic Necrosis Virus infection in Sockeye Salmon Populations
Description
Disease has been identified among a list of factors that may be responsible for declines of Fraser River Sockeye Salmon. There are a variety of pathogens causing disease and death in Sockeye Salmon and among these, infectious hematopoietic necrosis virus (IHNV) is recognized as a lethal contagion. Key questions remain about IHNV regarding the origins, transmission and impact of the virus across salmonid species and stocks. It has been suggested that IHNV is maintained in salmon populations by persisting over the life of its host and/or by residing in species other than its susceptible hosts. Understanding how IHNV is maintained within Sockeye Salmon populations and what triggers disease development is the first step in understanding what, if any, role IHNV plays in the population dynamics of Sockeye Salmon.
This three year genomics study investigated IHNV in salmonids to examine:
- how IHNV is maintained in fish populations;
- whether Sockeye that were exposed to the virus and did not succumb to disease became carriers of IHNV; and
- what environmental factors triggered a switch from carrier to disease state.
Among contributions to new knowledge, the study was designed to identify the best Sockeye Salmon tissues to use for IHNV disease detection. This could be used to inform next generation fisheries management computer models that will take into account the health and disease status of salmon for more precise estimates of salmon aquaculture escapement as well as help determine the prevalence of IHNV in Fraser River wild salmon populations.
Results: Researchers began the work of illustrating the effect of IHNV in Sockeye by first developing a new highly sensitive IHNV diagnostic tool which was used to track the presence of IHNV in Sockeye Salmon after being exposed to the virus.
In a small percentage of those fish surviving IHN virus exposure, the virus was detected despite the absence of disease. These persistent virus infections, when identified in Sockeye Salmon, were linked with a unique brain function that suggested an ongoing adaptive immune (antibody-driven) response. However, despite this response, IHNV carriers displayed little sign of having an impaired ability in mounting an efficient innate (inherited) antiviral response when exposed to a viral mimic. The capacity of IHNV to reside in hosts that show no symptoms supports a virus carrier hypothesis and if proven infectious, could have significant consequences towards maintaining and spreading IHNV among susceptible host populations.
Scientific title for this project:
Characterization of infectious hematopoietic necrosis virus (IHNV) carrier state in sockeye salmon using genomic tools
Program Name
Genomics Research and Development Initiative (GRDI)
Year(s)
2011 - 2014
Principal Investigator(s)
Kyle Garver
lead
Stewart Johnson
Fisheries and Oceans Canada
Ben Koop
University of Victoria, Canada Research Chair, Departments of Biology, Division of Medical Sciences
Scott LaPatra
Director of Research and Development, Clear Springs Foods
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