Annual Recurrences of Viral Hemorrhagic Septicemia Epizootics in Age 0 Pacific Herring Clupea pallasii Valenciennes, 1847

Throughout a 20 year biosurveillance period, viral hemorrhagic septicemia virus was isolated in low titers from only 6/7355 opportunistically sampled adult Pacific herring, reflecting the typical endemic phase of the disease when the virus persists covertly. However, more focused surveillance efforts identified the presence of disease hot spots occurring among juvenile life history stages from certain nearshore habitats. These outbreaks sometimes recurred annually in the same temporal and spatial patterns and were characterized by infection prevalence as high as 96%. Longitudinal sampling indicated that some epizootics were relatively transient, represented by positive samples on a single sampling date, and others were more protracted, with positive samples occurring throughout the first 10 weeks of the juvenile life history phase. These results indicate that viral hemorrhagic septicemia (VHS) epizootics in free-ranging Pacific herring C. pallasii are more common than previously appreciated; however, they are easily overlooked if biosurveillance efforts are not designed around times and locations with high disease potential.

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Principles underlying the epizootiology of viral hemorrhagic septicemia in Pacific herring and other fishes throughout the North Pacific Ocean

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2015-0417 ◽

2016 ◽

Vol 73 (5) ◽

pp. 853-859 ◽

Cited By ~ 5

Author(s):

Paul K. Hershberger ◽

Kyle A. Garver ◽

James R. Winton

Keyword(s):

Pacific Ocean ◽

North Pacific Ocean ◽

Natural Populations ◽

Field Studies ◽

Viral Hemorrhagic Septicemia Virus ◽

Infection Prevalence ◽

Intensity Increase ◽

Pacific Herring ◽

Viral Hemorrhagic Septicemia ◽

The North

Although viral hemorrhagic septicemia virus (VHSV) typically occurs at low prevalence and intensity in natural populations of Pacific herring (Clupea pallasii) and other marine fishes in the Northeast Pacific Ocean, epizootics of the resulting disease (VHS) periodically occur, often in association with observed fish kills. Here we identify a list of principles, based on a combination of field studies, controlled laboratory experiments, and previously unpublished observations, that govern the epizootiology of VHS in Pacific herring. A thorough understanding of these principles provides the basis for identifying risk factors that predispose certain marine fish populations to VHS epizootics, including the lack of population resistance, presence of chronic viral carriers in a population, copious viral shedding by infected individuals, cool water temperatures, limited water circulation patterns, and gregarious host behavioral patterns. Further, these principles are used to define the epizootiological stages of the disease in Pacific herring, including the susceptible (where susceptible individuals predominate a school or subpopulation), enzootic (where infection prevalence and intensity are often below the limits of reasonable laboratory detection), disease amplification (where infection prevalence and intensity increase rapidly), outbreak (often accompanied by host mortalities with high virus loads and active shedding), recovery (in which the mortality rate and virus load decline owing to an active host immune response), and refractory stages (characterized by little or no susceptibility and where viral clearance occurs in most VHS survivors). In addition to providing a foundation for quantitatively assessing the potential risks of future VHS epizootics in Pacific herring, these principles provide insights into the epizootiology of VHS in other fish communities where susceptible species exist.

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Introduction to studies on the effects of the (E××on Valdez) oil spill on early life history stages of Pacific herring, (Clupea pallasi), in Prince William Sound, Alaska

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-53-10-2337 ◽

1996 ◽

Vol 53 (10) ◽

pp. 2337-2342 ◽

Cited By ~ 2

Author(s):

E.D. Brown ◽

B.L. Norcross ◽

J.W. Short

Keyword(s):

Life History ◽

Oil Spill ◽

Early Life ◽

Early Life History ◽

Pacific Herring ◽

Prince William Sound ◽

Clupea Pallasi ◽

Life History Stages

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Expression of viral hemorrhagic septicemia virus in prespawning Pacific herring (Clupea pallasi) exposed to weathered crude oil

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f98-116 ◽

1998 ◽

Vol 55 (10) ◽

pp. 2300-2309 ◽

Cited By ~ 20

Author(s):

M G Carls ◽

G D Marty ◽

T R Meyers ◽

R E Thomas ◽

S D Rice

Keyword(s):

Crude Oil ◽

Immune Surveillance ◽

Inflammatory Cells ◽

Viral Hemorrhagic Septicemia Virus ◽

Pacific Herring ◽

Toxicant Exposure ◽

Clupea Pallasi ◽

Viral Hemorrhagic Septicemia ◽

Unknown Status ◽

Splenic Thrombosis

Expression of subclinical viral infection in response to toxicant exposure has not previously been reported, but evidence presented herein indicates that activation of viral hemorrhagic septicemia virus (VHSV) may occur in Pacific herring (Clupea pallasi) exposed to crude oil encountered after an oil spill. Decreased incidence of hepatic inflammatory cells as a function of total polynuclear aromatic hydrocarbon (TPAH) concentration was evidence for immunosuppression in exposed fish, and decreased immune surveillance is a possible mechanism by which subclinical VHSV could be reactivated. Adult Pacific herring of unknown status regarding infection by VHSV were captured from the wild and exposed to weathered crude oil for 16-18 days. TPAH concentration in tissue, VHSV prevalence, and mortality were correlated with dose. Histopathologic lesions were significantly correlated with TPAH concentration and prevalence of VHSV, but not gender or length. Significant lesions included increased hepatocellular necrosis, splenic thrombosis, and decreased inflammation in the liver.

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