Survival and viral load of chinook salmon, sockeye salmon, and steelhead trout exposed to 4 genogroups of infectious hematopoietic necrosis virus (IHNV)

Dates

Publication Date: 2022-09-06
Start Date: 2017-05-25
End Date: 2022-08-10

Citation

McKenney, D., Páez, D.J., Kurath, G., Salzer, J.E., Purcell, M.K., and Naish, K.A., 2022, Survival and viral load of chinook salmon, sockeye salmon, and steelhead trout exposed to 4 genogroups of infectious hematopoietic necrosis virus (IHNV): U.S. Geological Survey data release, https://doi.org/10.5066/P98UQLLW.

Summary

Theory of the evolution of pathogen specialization suggests that a specialist pathogen gains high fitness in one host, but this comes with fitness loss in other hosts. By contrast, a generalist pathogen does not achieve high fitness in any host, but gains ecological fitness by exploiting different hosts, and has higher fitness than specialists in non-specialized hosts. As a result, specialist pathogens are predicted to have greater variation in fitness across hosts, and generalists would have lower fitness variation across hosts. We test these hypotheses by measuring pathogen replicative fitness as within-host viral loads from the onset of infection to the beginning of virus clearance, using the rhabdovirus infectious hematopoietic [...]

Summary

Theory of the evolution of pathogen specialization suggests that a specialist pathogen gains high fitness in one host, but this comes with fitness loss in other hosts. By contrast, a generalist pathogen does not achieve high fitness in any host, but gains ecological fitness by exploiting different hosts, and has higher fitness than specialists in non-specialized hosts. As a result, specialist pathogens are predicted to have greater variation in fitness across hosts, and generalists would have lower fitness variation across hosts. We test these hypotheses by measuring pathogen replicative fitness as within-host viral loads from the onset of infection to the beginning of virus clearance, using the rhabdovirus infectious hematopoietic necrosis virus (IHNV) in salmonid fish. Based on field prevalence and virulence studies, IHNV subgroups UP, MD, and L are specialists, causing infection and mortality in sockeye salmon, steelhead, and Chinook salmon juveniles, respectively. The UC subgroup evolved naturally from a UP ancestor and is a generalist infecting all three host species but without causing severe disease. We show that specialist subgroups had highest peak and mean viral loads in the hosts in which they are specialized, and they had low viral loads in non-specialized hosts, resulting in large variation in viral load across hosts. Viral kinetics show that the mechanisms of specialization involve both the ability to maximize early virus replication and to avoid clearance at later times, with different mechanisms of specialization evident in different host-virus combinations. Additional nuances in the data included different fitness levels for non-specialist interactions, reflecting different trade-offs for specialist viruses in other hosts. The generalist UC subgroup reached intermediate viral loads in all hosts and showed the smallest variation in fitness across hosts. Evolution of the UC generalist from an ancestral UP sockeye specialist was associated with fitness increases in steelhead and Chinook salmon, but only slight decrease in fitness in sockeye salmon, consistent with low- or no-cost generalism. Our results support major elements of specialist-generalist theory, providing evidence of a specialist-generalist continuum in a vertebrate pathogen. These results also quantify within-host replicative fitness tradeoffs resulting from the natural evolution of specialist and generalist virus lineages in multi-host ecosystems.

Contacts

Point of Contact :: Gael Kurath
Originator :: Douglas G Mckenney, David J. Páez, Gael Kurath, Joanne E Salzer, Maureen K Purcell, Kerry A. Naish
Metadata Contact :: Gael Kurath
Publisher :: U.S. Geological Survey
Distributor :: U.S. Geological Survey - ScienceBase
SDC Data Owner :: Western Fisheries Research Center
USGS Mission Area :: Ecosystems

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IK_metadata.xml “Metadata describing data collected to evaluate in vivo IHNV replication kinetics” Original FGDC Metadata	View	102.1 KB	application/fgdc+xml
Infection Kinetics IHNV Mortality.xlsx “Daily mortalities during in vivo challenge ”		20.34 KB	application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Infection Kinetics IHNV Viral Load.xlsx “IHNV qPCR results from fish collected during in vivo challenge”		146.53 KB	application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

Related External Resources

Type: Related Primary Publication

David J Páez, Douglas McKenney, Maureen K Purcell, Kerry A Naish, Gael Kurath, Variation in Within-Host Replication Kinetics Among Virus Genotypes Provides Evidence of Specialist and Generalist Infection Strategies Across Three Salmonid Host Species, Virus Evolution, 2022;, veac079, https://doi.org/10.1093/ve/veac079	https://doi.org/10.1093/ve/veac079

Purpose

Data were collected to define within-host replication kinetics for UP, UC, MD, and L IHNV in chinook salmon, sockeye salmon, and steelhead trout.

Survival and viral load of chinook salmon, sockeye salmon, and steelhead trout exposed to 4 genogroups of infectious hematopoietic necrosis virus (IHNV)

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