Abstract
Simple SummaryPathogen surveillances in wild marine fish populations need to be carefully designed to address specific research or management objectives. Surveillance strategies should be designed around host life history characteristics, host and pathogen geographic ranges, laboratory diagnostic tools that are specific to the epidemiology of each pathogen, and the goal of the surveillance program. We demonstrate how the potential impacts of viral hemorrhagic septicemia can be under-appreciated in populations of Pacific herring by comparing results from opportunistically collected samples with those from more targeted epidemiological investigations that were focused on times and locations with high disease probability.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.
Highlights
Viral hemorrhagic septicemia virus, genogroup IVa has a broad host range in marine fishes throughout the coastal waters of North America and Asia, including China, Japan, and Korea [1,2,3]
Genogroup IVa has a broad host range in marine fishes throughout the coastal waters of North America and Asia, including China, Japan, and Korea [1,2,3]. Throughout parts of this range, the ecology of the virus is closely tied to Pacific herring (Clupea pallasii Valenciennes, 1847) and other hosts [4] which are highly susceptible to the resulting disease and serve as effective reservoirs between outbreaks [5]
viral hemorrhagic septicemia (VHS) virus occurs in Pacific herring C. pallasii from Puget Sound, Washington, USA, where the disease sometimes occurs in confined wild cohorts [6,7], epizootics among free-ranging herring have not yet been reported from this region [8]
Summary
Genogroup IVa (hereafter referred to as VHS virus) has a broad host range in marine fishes throughout the coastal waters of North America and Asia, including China, Japan, and Korea [1,2,3] Throughout parts of this range, the ecology of the virus is closely tied to Pacific herring (Clupea pallasii Valenciennes, 1847) and other hosts [4] which are highly susceptible to the resulting disease (viral hemorrhagic septicemia; VHS) and serve as effective reservoirs between outbreaks [5]. It is important to recognize that most epizootics go unnoticed because they remain small in scale and/or they occur in remote locations that are difficult to sample Because of these logistical challenges, reports of VHS epizootics in wild marine fishes generally describe single sample collections from reported fish kills. To emphasize the ease with which these epizootics can be overlooked, we report the results from 20 years of VHS virus surveillances in Pacific herring C. pallasii populations throughout the NE Pacific Ocean, including annual sampling from pre-spawn aggregations in Prince William Sound and Sitka Sound as well as opportunistic sampling from other locations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
