Dataset Information

Densovirus associated with sea-star wasting disease and mass mortality.

ABSTRACT: Populations of at least 20 asteroid species on the Northeast Pacific Coast have recently experienced an extensive outbreak of sea-star (asteroid) wasting disease (SSWD). The disease leads to behavioral changes, lesions, loss of turgor, limb autotomy, and death characterized by rapid degradation ("melting"). Here, we present evidence from experimental challenge studies and field observations that link the mass mortalities to a densovirus (Parvoviridae). Virus-sized material (i.e., <0.2 ?m) from symptomatic tissues that was inoculated into asymptomatic asteroids consistently resulted in SSWD signs whereas animals receiving heat-killed (i.e., control) virus-sized inoculum remained asymptomatic. Viral metagenomic investigations revealed the sea star-associated densovirus (SSaDV) as the most likely candidate virus associated with tissues from symptomatic asteroids. Quantification of SSaDV during transmission trials indicated that progression of SSWD paralleled increased SSaDV load. In field surveys, SSaDV loads were more abundant in symptomatic than in asymptomatic asteroids. SSaDV could be detected in plankton, sediments and in nonasteroid echinoderms, providing a possible mechanism for viral spread. SSaDV was detected in museum specimens of asteroids from 1942, suggesting that it has been present on the North American Pacific Coast for at least 72 y. SSaDV is therefore the most promising candidate disease agent responsible for asteroid mass mortality.

SUBMITTER: Hewson I

PROVIDER: S-EPMC4260605 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Densovirus associated with sea-star wasting disease and mass mortality.

Hewson Ian I Button Jason B JB Gudenkauf Brent M BM Miner Benjamin B Newton Alisa L AL Gaydos Joseph K JK Wynne Janna J Groves Cathy L CL Hendler Gordon G Murray Michael M Fradkin Steven S Breitbart Mya M Fahsbender Elizabeth E Lafferty Kevin D KD Kilpatrick A Marm AM Miner C Melissa CM Raimondi Peter P Lahner Lesanna L Friedman Carolyn S CS Daniels Stephen S Haulena Martin M Marliave Jeffrey J Burge Colleen A CA Eisenlord Morgan E ME Harvell C Drew CD

Proceedings of the National Academy of Sciences of the United States of America 20141117 48

Populations of at least 20 asteroid species on the Northeast Pacific Coast have recently experienced an extensive outbreak of sea-star (asteroid) wasting disease (SSWD). The disease leads to behavioral changes, lesions, loss of turgor, limb autotomy, and death characterized by rapid degradation ("melting"). Here, we present evidence from experimental challenge studies and field observations that link the mass mortalities to a densovirus (Parvoviridae). Virus-sized material (i.e., <0.2 μm) from s ...[more]

PMID: 25404293

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Project description:A viral etiology of sea star wasting syndrome (SSWS) was originally explored with virus-sized material challenge experiments, field surveys, and metagenomics, leading to the conclusion that a densovirus is the predominant DNA virus associated with this syndrome and, thus, the most promising viral candidate pathogen. Single-stranded DNA viruses are, however, highly diverse and pervasive among eukaryotic organisms, which we hypothesize may confound the association between densoviruses and SSWS. To test this hypothesis and assess the association of densoviruses with SSWS, we compiled past metagenomic data with new metagenomic-derived viral genomes from sea stars collected from Antarctica, California, Washington, and Alaska. We used 179 publicly available sea star transcriptomes to complement our approaches for densovirus discovery. Lastly, we focus the study on sea star-associated densovirus (SSaDV), the first sea star densovirus discovered, by documenting its biogeography and putative tissue tropism. Transcriptomes contained only endogenized densovirus elements similar to the NS1 gene, while numerous extant densoviral genomes were recovered from viral metagenomes. SSaDV was associated with nearly all tested species from southern California to Alaska, and in contrast to previous work, we show that SSaDV is one genotype among a high diversity of densoviruses present in sea stars across the West Coast of the United States and globally that are commonly associated with grossly normal (i.e., healthy or asymptomatic) animals. The diversity and ubiquity of these viruses in sea stars confound the original hypothesis that one densovirus is the etiological agent of SSWS.IMPORTANCE The primary interest in sea star densoviruses, specifically SSaDV, has been their association with sea star wasting syndrome (SSWS), a disease that has decimated sea star populations across the West Coast of the United States since 2013. The association of SSaDV with SSWS was originally drawn from metagenomic analysis, which was further studied through field surveys using quantitative PCR (qPCR), with the conclusion that it was the most likely viral candidate in the metagenomic data based on its representation in symptomatic sea stars compared to asymptomatic sea stars. We reexamined the original metagenomic data with additional genomic data sets and found that SSaDV was 1 of 10 densoviruses present in the original data set and was no more represented in symptomatic sea stars than in asymptomatic sea stars. Instead, SSaDV appears to be a widespread, generalist virus that exists among a large diversity of densoviruses present in sea star populations.

Project description:Disease outbreaks can have substantial impacts on wild populations, but the often patchy or anecdotal evidence of these impacts impedes our ability to understand outbreak dynamics. Recently however, a severe disease outbreak occurred in a group of very well-studied organisms-sea stars along the west coast of North America. We analyzed nearly two decades of data from a coordinated monitoring effort at 88 sites ranging from southern British Columbia to San Diego, California along with 2 sites near Sitka, Alaska to better understand the effects of sea star wasting disease (SSWD) on the keystone intertidal predator, Pisaster ochraceus. Quantitative surveys revealed unprecedented declines of P. ochraceus in 2014 and 2015 across nearly the entire geographic range of the species. The intensity of the impact of SSWD was not uniform across the affected area, with proportionally greater population declines in the southern regions relative to the north. The degree of population decline was unrelated to pre-outbreak P. ochraceus density, although these factors have been linked in other well-documented disease events. While elevated seawater temperatures were not broadly linked to the initial emergence of SSWD, anomalously high seawater temperatures in 2014 and 2015 might have exacerbated the disease's impact. Both before and after the onset of the SSWD outbreak, we documented higher recruitment of P. ochraceus in the north than in the south, and while some juveniles are surviving (as evidenced by transition of recruitment pulses to larger size classes), post-SSWD survivorship is lower than during pre-SSWD periods. In hindsight, our data suggest that the SSWD event defied prediction based on two factors found to be important in other marine disease events, sea water temperature and population density, and illustrate the importance of surveillance of natural populations as one element of an integrated approach to marine disease ecology. Low levels of SSWD-symptomatic sea stars are still present throughout the impacted range, thus the outlook for population recovery is uncertain.

Project description:Disease emergence occurs within the context of ecological communities, and disease driven declines in host populations can lead to complex direct and indirect ecological effects. Varying effects of a single disease among multiple susceptible hosts could benefit relatively resistant species. Beginning in 2013, an outbreak of sea star wasting disease (SSWD) led to population declines of many sea star species along the west coast of North America. Through field surveys and laboratory experiments, we investigated how and why the relative abundances of two co-occurring sea star species, Evasterias troschelii and Pisaster ochraceus, shifted during the ongoing wasting epidemic in Burrard Inlet, British Columbia, Canada. We hypothesized that Evasterias is competitively inferior to Pisaster but more resistant to SSWD. Thus, we predicted that SSWD-induced declines of Pisaster could mitigate the negative effects of SSWD on Evasterias, as the latter would experience competitive release. We document shifts in sea star abundance from 2008-2017: Pisaster abundance and mean size declined during the outbreak, while Evasterias abundance increased from relatively rare to numerically dominant within the intertidal. When exposed to symptomatic sea stars, Pisaster and Evasterias both showed signs of SSWD, but transmission and susceptibility was lower in Evasterias. Despite diet overlap documented in our field surveys, Evasterias was not outcompeted by Pisaster in laboratory trails conducted with the relatively small Pisaster available after the outbreak. Interference competition with larger Pisaster, or prey exploitation by Pisaster during the summer when Evasterias is primarily subtidal, may explain the rarity of Evasterias prior to Pisaster declines. Our results suggest that indirect effects mediated by competition can mask some of the direct effects of disease outbreaks, and the combination of direct and indirect effects will determine the restructuring of a community after disturbance.

Dataset Information

Densovirus associated with sea-star wasting disease and mass mortality.

Publications

Densovirus associated with sea-star wasting disease and mass mortality.

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