Factors Affecting Pathogenicity of Infectious Hematopoietic Necrosis Virus (IHNV) for Salmonid Fish

LaPatra, Scott E.

doi:10.1577/1548-8667(1998)010<0121:fapoih>2.0.co;2

Cited by 89 publications

(85 citation statements)

References 43 publications

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“…Ultimately, overall viral fitness is not a fixed parameter and varies based on a variety of complex factors, including host density, population structure, supply rate of naïve hosts, contact rates, and an array of environmental conditions, including temperature and water flow rate (4,25,30,32). Here, we provided the first steps toward assessing whether virulence will be selected by determining what pathogen fitness traits are associated with virulence.…”

Section: Discussionmentioning

confidence: 99%

In Vivo Fitness Associated with High Virulence in a Vertebrate Virus Is a Complex Trait Regulated by Host Entry, Replication, and Shedding

Wargo

Kurath

2011

J Virol

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The relationship between pathogen fitness and virulence is typically examined by quantifying only one or two pathogen fitness traits. More specifically, it is regularly assumed that within-host replication, as a precursor to transmission, is the driving force behind virulence. In reality, many traits contribute to pathogen fitness, and each trait could drive the evolution of virulence in different ways. Here, we independently quantified four viral infection cycle traits, namely, host entry, within-host replication, within-host coinfection fitness, and shedding, in vivo, in the vertebrate virus Infectious hematopoietic necrosis virus (IHNV). We examined how each of these stages of the viral infection cycle contributes to the fitness of IHNV genotypes that differ in virulence in rainbow trout. This enabled us to determine how infection cycle fitness traits are independently associated with virulence. We found that viral fitness was independently regulated by each of the traits examined, with the largest impact on fitness being provided by within-host replication. Furthermore, the more virulent of the two genotypes of IHNV we used had advantages in all of the traits quantified. Our results are thus congruent with the assumption that virulence and within-host replication are correlated but suggest that infection cycle fitness is complex and that replication is not the only trait associated with virulence.Despite a recent surge in research, the evolution of viral virulence remains a controversial issue (1,7,10,18,22,37,50,60). Some studies have suggested a positive link between viral fitness and virulence (6, 13, 17, 39, 42, 49, 52-54, 58, 59), whereas others found no evidence of such an association (20,24,27) or even indicated that the converse, that virulence is negatively associated with viral fitness, is true (36, 43). Despite the fact that these studies span a wide range of virus and host taxa, a limitation of many of these studies is that viral fitness was typically estimated from only one or two virus traits, at one stage of the viral infection cycle. In reality, viral fitness is likely shaped by multiple traits at each of the viral infection stages, i.e., entry into the host, replication in the host, and shedding from the host, all of which could differentially impact selection for virulence (5).Most estimates of viral fitness come from examinations of the within-host replication stage of the viral infection cycle. For a few systems, researchers have made an effort to provide a detailed assessment of the importance of within-host dynamics on fitness, by separately quantifying replication in single-genotype infections and the relative abilities of virus genotypes to produce infectious progeny in a coinfection environment, herein referred to as coinfection fitness (15,39,59). However, the connection between within-host fitness and transmission remains elusive (20, 24, 42, 52), partly due to an incomplete understanding of virus investment into shedding and entry (8,45). These limitations are compounded in verteb...

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Section: Discussionmentioning

confidence: 99%

In Vivo Fitness Associated with High Virulence in a Vertebrate Virus Is a Complex Trait Regulated by Host Entry, Replication, and Shedding

Wargo

Kurath

2011

J Virol

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“…Virus concentrations up to 10 3 plaque forming units (PFU) have been detected in the natural environment of salmonids [37] and are less than the 6.4 Â 10 5 TCID 50 mL À1 challenge dose in our study. Although immersion challenge with IHNV at higher concentrations has been demonstrated to induce infections in both juvenile and adult salmonids [38,39], subsequent mortality may be highly variable due to a range of factors dependent on the host, environment, and virus used [40]. Fish age is one critical factor, and salmonids younger than two months are considered the most susceptible to the virus [40].…”

Section: Discussionmentioning

confidence: 99%

Expression of immune-regulatory genes in juvenile Chinook salmon following exposure to pesticides and infectious hematopoietic necrosis virus (IHNV)

Eder

Clifford

Hedrick

et al. 2008

Fish & Shellfish Immunology

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“…The manifestation of IHN disease also depends on the size/age of the fish, water temperature, season and environmental conditions -factors which can all heavily affect the immune response in fish (LaPatra 1998). In this study, rainbow trout resistant to a waterborne VHSV infection were kept under defined conditions and were infected with European and North American isolates of IHNV.…”

Section: Introductionmentioning

confidence: 99%

Age- and weight-dependent susceptibility of rainbow trout Oncorhynchus mykiss to isolates of infectious haematopoietic necrosis virus (IHNV) of varying virulence

Bergmann

Fichtner²,

Skall

et al. 2003

Dis. Aquat. Org.

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The virulence of 5 European and 1 North American isolate of infectious haematopoietic necrosis virus (IHNV) was compared by infecting female sibling rainbow trout ('Isle of Man' strain) of different weights and ages (2, 20 and 50 g). The fish were exposed to 10 4 TCID 50 IHNV per ml of water by immersion, and the mortality was recorded for 28 d. Two new IHNV isolates from Germany were included in the investigation. One was isolated from European eels kept at 23°C (± 2°C) and the other was not detectable by immunofluorescence with commercially available monoclonal antibodies recognising the viral G protein. The results showed that IHNV isolates of high or low virulence persisted in rainbow trout of all ages/weights for 28 d, with the exception of fish over 15 g in the eel IHNV (DF [diagnostic fish] 13/98)-infected groups from which the virus could not be reisolated on Day 28. The smallest fish were most susceptible to an infection with any of the IHNV isolates. The lowest cumulative mortality (18%) was observed in fingerlings infected with the North American isolate HAG (obtained from Hagerman Valley), and the highest mortality (100%) in DF 04/99 infected fish. The DF 04/99 and Ö-13/95 viruses caused mortality in fish independent of their weight or age. The isolates FR-32/87 and I-4008 were virulent in fish up to a weight of 20 g and caused no mortality in larger fish. In the IHNV HAG-and DF 13/98 (eel)-infected rainbow trout, no signs of disease were observed in fish weighing between 15 and 50 g. An age/weight related susceptibility of rainbow trout was demonstrated under the defined conditions for all IHNV isolates tested.

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Factors Affecting Pathogenicity of Infectious Hematopoietic Necrosis Virus (IHNV) for Salmonid Fish

Cited by 89 publications

References 43 publications

In Vivo Fitness Associated with High Virulence in a Vertebrate Virus Is a Complex Trait Regulated by Host Entry, Replication, and Shedding

In Vivo Fitness Associated with High Virulence in a Vertebrate Virus Is a Complex Trait Regulated by Host Entry, Replication, and Shedding

Expression of immune-regulatory genes in juvenile Chinook salmon following exposure to pesticides and infectious hematopoietic necrosis virus (IHNV)

Age- and weight-dependent susceptibility of rainbow trout Oncorhynchus mykiss to isolates of infectious haematopoietic necrosis virus (IHNV) of varying virulence

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