Bucci C et al. (2017), Sea Star Wasting Disease in Asterias forbesi al...

ECB-ART-45924

PLoS One 2017 Jan 01;1212:e0188523. doi: 10.1371/journal.pone.0188523.

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Sea Star Wasting Disease in Asterias forbesi along the Atlantic Coast of North America.

Bucci C , Francoeur M , McGreal J , Smolowitz R , Zazueta-Novoa V , Wessel GM , Gomez-Chiarri M .

Abstract
As keystone species, sea stars serve to maintain biodiversity and species distribution through trophic level interactions in marine ecosystems. Recently, Sea Star Wasting Disease (SSWD) has caused widespread mass mortality in several sea star species from the Pacific Coast of the United States of America (USA) and Asterias forbesi on the Atlantic Coast. A densovirus, named Sea Star associated Densovirus (SSaDV), has been associated with the wasting disease in Pacific Coast sea stars, and limited samples of A. forbesi. The goal of this research is to examine the pathogenesis of SSWD in A. forbesi on the Atlantic Coast of the USA and to determine if SSaDV is associated with the wasting disease in this species. Histological examination of A. forbesi tissues affected with SSWD showed cuticle loss, vacuolation and necrosis of epidermal cells, and oedema of the dermis, but no consistent evidence indicating the cause of the lesions. Challenge experiments by cohabitation and immersion in infected water suggest that the cause of SSWD is viral in nature, as filtration (0.22 μm) of water from tanks with sea stars exhibiting SSWD did not prevent the transmission and progression of the disease. Death of challenged sea stars occurred 7-10 d after exposure to infected water or sea stars, and the infectivity crossed species (A. forbesi and Pateria miniata) with equal penetrance. Of the 48 stars tested by quantitative real time PCR, 29 (60%) were positive for the SSaDV VP1 gene. These stars represent field-collected sea stars from all geographical regions (South Carolina to Maine) in 2012-2015, as well as stars exposed to infected stars or water from affected tanks. However, a clear association between the presence of SSaDV and SSWD signs in experimental and field-collected A. forbesi was not found in this study.

PubMed ID: 29228006
PMC ID: PMC5724889
Article link: PLoS One
Grant support: [+]

Genes referenced: LOC100887844 LOC100893907

Article Images: [+] show captions

	Fig 1. Timeline of SSWD events in sea stars on the Atlantic Coast of the USA.The timeline summarizes reports of events observed in aquariums (in blue) and citizen reports (green) in response to questionnaires administered in 2013 to 2015.
	Fig 2. Gross morphological signs of Sea Star Wasting Disease.Representative images of A. forbesi affected with wasting disease showing combinations of different clinical signs (A-F). Clinical signs are indicated by arrows, and included (a) limb curling, (b) mucoid-like aboral surface coat, (c) pinching, (d) small ulcerations shown as white pinpoint lesions, (e) loss of spine orientation, and (f) severe ulcerations leading to exposure of underlying tissues.

	Fig 4. Average colony forming units (CFU/mL) of bacteria from Forbes stars with or without signs of SSWD.Culturable bacteria (individual sample values and average CFU/mL Â± SEM) from swabs obtained from stars with visible SSWD lesions (lesion +) and those with no visible lesions (lesion -).
	Fig 5. Time to morbidity and mortality in experimentally challenged Forbes sea stars.Time in days to observation of the first clinical signs of SSWD (A) and mortality (B) in challenged stars. Each symbol represents an individual star. Plots also show the average Â± SEM (horizontal and vertical lines respectively). The cumulative percent mortality in each treatment is also shown in (B). Treatments (on the x axis) were: B = Immersion challenge with a Roseobacter sp. Isolate (n = 4); CSS = Cohabitation of healthy-looking A. forbesi with stars with signs of SSWD (all experiments combined, n = 30); CSU = Cohabitation of healthy-looking Forbes sea stars (n = 3) with a sea urchin from the Maine Aquarium; CSC = Cohabitation of sea stars (n = 6) with 2 sea cucumbers from the Maine Aquarium; FW = Immersion in filtered (0.22 Î¼m) infected water (n = 8); IW = Immersion in infected water (n = 8).
	Fig 6. SSaDV VP1 copy number in field Forbes sea stars from 3 locations on the Atlantic Coast of the USA.Concentration of SSaDV VP1 (copy number/Î¼L) in all sea stars collected in different locations from the Atlantic Coast of the USA between 2013 and 2015. Plot shows individual values for each sample (symbols) as well as the mean (line). RI BV: Beavertail, RI; RI GSO: Pier at the Graduate School of Oceanography, RI; SC: Charleston, SC (3 d after arrival).
	Fig 7. SSaDV VP1 copy number in field collected and experimentally challenged stars.Comparison of the concentration of SSaDV VP1 (copy number/Î¼L) in A. forbesi collected from the field (n = 34) and from experimental challenges (n = 14). Plots represent individual values for each sample (symbols) and the mean (line).
	Fig 8. Change in SSaDV VP1 copy number in sea stars during progression of SSWD.Comparison of VP1 copy number per sample in sea stars received from the field in Chaleston, SC. Between the day of arrival (day 1) and day 3 after placement of the stars in quarantine/isolated tanks containing filtered UV-treated artifical sea water. Plots represent individual values for each sample (symbols) as well as the mean (line).

References [+] :

Bates, Effects of temperature, season and locality on wasting disease in the keystone predatory sea star Pisaster ochraceus. 2009, Pubmed, Echinobase