Method for serial passage of infectious hematopoietic necrosis virus (IHNV) in rainbow trout

Doumayrou, Juliette; Ryan, M Gray; Wargo, Andrew R.

doi:10.3354/dao03368

Cited by 8 publications

(8 citation statements)

References 71 publications

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“…There was no evidence that reductions in recovery rate are outweighed by truncation of host lifespan at the virulence levels studied here. This is likely because shedding of the virus is very acute and mostly occurs before mortality begins [82][83][84].…”

Section: Plos Pathogensmentioning

confidence: 99%

“…The raceway volume (183,219 L), and water exchange rate (72 flushes/day), were chosen to represent conditions on a typical North American trout farm [134][135][136][137]. Transmission is also assumed to be driven by fish contact with virus particles in the water [69][70][71][72][73][74][75][82][83][84]. Recovery rate equaled 1/mean duration of shedding (last day-first day + 1) for fish infected with each IHNV genotype; calculated using Kaplan-Meier analysis (survfit) on experiment 1 data.…”

Section: Transmission Model Of Ihnv Genotypesmentioning

confidence: 99%

“…Dose response studies have characterized the relationship between viral concentration in the water and infectivity [68,[80][81][82]. As such, viral shedding quantification has been established as a proxy for transmission [82][83][84][85][86].…”

Section: Introductionmentioning

confidence: 99%

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Virus shedding kinetics and unconventional virulence tradeoffs

et al. 2021

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Tradeoff theory, which postulates that virulence provides both transmission costs and benefits for pathogens, has become widely adopted by the scientific community. Although theoretical literature exploring virulence-tradeoffs is vast, empirical studies validating various assumptions still remain sparse. In particular, truncation of transmission duration as a cost of virulence has been difficult to quantify with robust controlled in vivo studies. We sought to fill this knowledge gap by investigating how transmission rate and duration were associated with virulence for infectious hematopoietic necrosis virus (IHNV) in rainbow trout (Oncorhynchus mykiss). Using host mortality to quantify virulence and viral shedding to quantify transmission, we found that IHNV did not conform to classical tradeoff theory. More virulent genotypes of the virus were found to have longer transmission durations due to lower recovery rates of infected hosts, but the relationship was not saturating as assumed by tradeoff theory. Furthermore, the impact of host mortality on limiting transmission duration was minimal and greatly outweighed by recovery. Transmission rate differences between high and low virulence genotypes were also small and inconsistent. Ultimately, more virulent genotypes were found to have the overall fitness advantage, and there was no apparent constraint on the evolution of increased virulence for IHNV. However, using a mathematical model parameterized with experimental data, it was found that host culling resurrected the virulence tradeoff and provided low virulence genotypes with the advantage. Human-induced or natural culling, as well as host population fragmentation, may be some of the mechanisms by which virulence diversity is maintained in nature. This work highlights the importance of considering non-classical virulence tradeoffs.

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Section: Plos Pathogensmentioning

confidence: 99%

Section: Transmission Model Of Ihnv Genotypesmentioning

confidence: 99%

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Virus shedding kinetics and unconventional virulence tradeoffs

et al. 2021

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“…Overall, vaccination reduced pathogen fitness by an order of magnitude or less (i.e., resulted in reduction in total shedding). If viral shedding is correlated with transmission as other studies have suggested (Wargo and Kurath 2012;Doumayrou et al 2019), this would imply that vaccinated hosts are still able to transmit the virus, despite experiencing little clinical disease. Epidemiologically, the ability of vaccinated individuals to transmit the disease could greatly hinder management and eradication of disease, particularly if there is transmission between vaccinated and unvaccinated fish (e.g., between wild and cultured populations; Troyer and Kurath 2003).…”

Section: Discussionmentioning

confidence: 98%

“…Host-to-host transmission through the entire infectious period is difficult to measure for IHNV and many other pathogens. However, previous studies have shown that IHNV transmission is correlated with the amount of virus shed from the host into the water (Doumayrou et al 2019). Here, we used viral shedding that was quantified at numerous time points throughout the infection as an estimate of transmission.…”

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confidence: 99%

Impact of Vaccination and Pathogen Exposure Dosage on Shedding Kinetics of Infectious Hematopoietic Necrosis Virus (IHNV) in Rainbow Trout

2020

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Vaccine efficacy in preventing clinical disease has been well characterized. However, vaccine impacts on transmission under diverse field conditions, such as variable pathogen exposure dosages, are not fully understood. We evaluated the impacts of vaccination on disease‐induced host mortality and shedding of infectious hematopoietic necrosis virus (IHNV) in Rainbow Trout Oncorhynchus mykiss. Fish, in up to three different genetic lines, were exposed to different dosages of IHNV to simulate field variability. Mortality and viral shedding of each individual fish were quantified over the course of infection. As the exposure dosage increased, mortality, number of fish shedding virus, daily virus quantity shed, and total amount of virus shed also increased. Vaccination significantly reduced mortality but had a much smaller impact on shedding, such that vaccinated fish still shed significant amounts of virus, particularly at higher viral exposure dosages. These studies demonstrate that the consideration of pathogen exposure dosage and transmission are critical for robust inference of vaccine efficacy.

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