Geology Reports⌕ Search
Home/Archive/USGS

USGS · 70164383

Increasing virulence, but not infectivity, associated with serially emergent virus strains of a fish rhabdovirus

Rachel Breyta·Douglas McKenney·Tarin Tesfaye·Kotaro Ono·Gael Kurath
View original source ↗Export metadata ↓

Abstract

Surveillance and genetic typing of field isolates of a fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), has identified four dominant viral genotypes that were involved in serial viral emergence and displacement events in steelhead trout ( Oncorhynchus mykiss ) in western North America. To investigate drivers of these landscape-scale events, IHNV isolates designated 007, 111, 110, and 139, representing the four relevant genotypes, were compared for virulence and infectivity in controlled laboratory challenge studies in five relevant steelhead trout populations. Viral virulence was assessed as mortality using lethal dose estimates (LD50), survival kinetics, and proportional hazards analysis. A pattern of increasing virulence for isolates 007, 111, and 110 was consistent in all five host populations tested, and correlated with serial emergence and displacements in the virus-endemic lower Columbia River source region during 1980–2013. The fourth isolate, 139, did not have higher virulence than the previous isolate 110. However, the mG139M genotype displayed a conditional displacement phenotype in that it displaced type mG110M in coastal Washington, but not in the lower Columbia River region, indicating that factors other than evolution of higher viral virulence were involved in some displacement events. Viral infectivity, measured as infectious dose (ID50), did not correlate consistently with virulence or with viral emergence, and showed a narrow range of variation relative to the variation observed in virulence. Comparison among the five steelhead trout populations confirmed variation in resistance to IHNV, but correlations with previous history of virus exposure or with sites of viral emergence varied between IHNV source and sink regions. Overall, this study indicated increasing viral virulence over time as a potential driver for emergence and displacement events in the endemic Lower Columbia River source region where these IHNV genotypes originated, but not in adjacent sink regions.

Explore related subjects

Virus EvolutionArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Rachel Breyta, Douglas McKenney, Tarin Tesfaye, Kotaro Ono, Gael Kurath. 2016-01-19. Increasing virulence, but not infectivity, associated with serially emergent virus strains of a fish rhabdovirus. https://doi.org/10.1093/ve%2Fvev018

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2025

Identification of novel hepaciviruses and Sylvilagus-associated viruses via metatranscriptomics in North American lagomorphs

Cottontails ( Sylvilagus spp.) and jackrabbits ( Lepus spp.) within the Leporidae family are native to North America and are found in a wide range of habitats, including deserts, forests, and grasslands. Although there is a growing body of research describing the arrival of the highly virulent rabbit haemorrhagic disease virus 2 (RHDV2, GI.2) on this continent, and its impact on native lagomorphs, information about the natural virome and microbiome of healthy and deceased American lagomorphs is relatively limited. In this study, we used a meta-transcriptomics approach to conduct whole pathogen profiling on healthy and deceased animals in the USA. We analysed 48 matched liver and lung sample pools from apparently healthy cottontails and jackrabbits in Texas and an additional 48 liver samples from deceased animals from nine other US states. This approach enabled the discovery of three distinct new viruses and revealed additional new insights into the lung and liver microbiomes of North American lagomorphs. Of the three new viruses, a tetnovirus and a novel picorna-like virus were likely of insect origin and therefore considered environmental contaminants. Of particular interest was a new species of hepacivirus, with around 50% sequence identity to a known hepacivirus from a xeric four-striped grass rat ( Rhabdomys pumilio ). Phylogenetic analysis from 41 individual hepacivirus genomes recovered from our lagomorph samples revealed two distinct clades, corresponding with different cottontail species. No hepaciviruses were detected in any of the jackrabbit samples. This is the first description of a hepacivirus in lagomorphs. Our findings extend the Hepacivirus genus, provide new insights into its evolution, and describe the first baseline on microbial diversity in North American lagomorphs, an important step towards understanding the role of potential pathogens for population management and conservation.

Arizona, California, Iowa, Massachusetts, Montana,↗
USGS2024

A meta-analysis highlights the idiosyncratic nature of tradeoffs in laboratory models of virus evolution

Different theoretical frameworks have been invoked to guide the study of virus evolution. Three of the more prominent ones are (i) the evolution of virulence, (ii) life history theory, and (iii) the generalism–specialism dichotomy. All involve purported tradeoffs between traits that define the evolvability and constraint of virus-associated phenotypes. However, as popular as these frameworks are, there is a surprising paucity of direct laboratory tests of the frameworks that support their utility as broadly applicable theoretical pillars that can guide our understanding of disease evolution. In this study, we conduct a meta-analysis of direct experimental evidence for these three frameworks across several widely studied virus–host systems: plant viruses, fungal viruses, animal viruses, and bacteriophages. We extracted 60 datasets from 28 studies and found a range of relationships between traits in different analysis categories (e.g., frameworks, virus–host systems). Our work demonstrates that direct evidence for relationships between traits is highly idiosyncratic and specific to the host–virus system and theoretical framework. Consequently, scientists researching viral pathogens from different taxonomic groups might reconsider their allegiance to these canons as the basis for expectation, explanation, or prediction. Future efforts could benefit from consistent definitions, and from developing frameworks that are compatible with the evidence and apply to particular biological and ecological contexts.

Virus Evolution↗
USGS2022

Habitat connectivity and host relatedness influence virus spread across an urbanising landscape in a fragmentation-sensitive carnivore

Spatially heterogeneous landscape factors such as urbanisation can have substantial effects on the severity and spread of wildlife diseases. However, research linking patterns of pathogen transmission to landscape features remains rare. Using a combination of phylogeographic and machine learning approaches, we tested the influence of landscape and host factors on feline immunodeficiency virus (FIV Lru ) genetic variation and spread among bobcats ( Lynx rufus ) sampled from coastal southern California. We found evidence for increased rates of FIV Lru lineage spread through areas of higher vegetation density. Furthermore, single-nucleotide polymorphism (SNP) variation among FIV Lru sequences was associated with host genetic distances and geographic location, with FIV Lru genetic discontinuities precisely correlating with known urban barriers to host dispersal. An effect of forest land cover on FIV Lru SNP variation was likely attributable to host population structure and differences in forest land cover between different populations. Taken together, these results suggest that the spread of FIV Lru is constrained by large-scale urban barriers to host movement. Although urbanisation at fine spatial scales did not appear to directly influence virus transmission or spread, we found evidence that viruses transmit and spread more quickly through areas containing higher proportions of natural habitat. These multiple lines of evidence demonstrate how urbanisation can change patterns of contact-dependent pathogen transmission and provide insights into how continued urban development may influence the incidence and management of wildlife disease.

California↗