Assessing the Pathogenic Cause of Sea Star Wasting Disease in Asterias Forbesi Along the East Coast of the United States

Abstract

As keystone predators, sea stars serve to maintain biodiversity and distribution through trophic level interactions in intertidal ecosystems. Sea Star Wasting Disease (SSWD) has caused widespread mass mortality of Asterias forbesi in locations along the Northeast Coast of the US in recent years. A similar disease has been described in several sea star species from the West Coast of the US. Recently, a densovirus has been associated with wasting disease in West Coast sea stars and a few limited samples of A. forbesi. The goal of this research is to describe the pathogenesis of SSWD in A. forbesi and other echinoderms in the Northeast Coast of the US and to determine if the densovirus isolated from West Coast sea stars (SSaDV) is associated with the SSWD of A. forbesi on the eastern US coast. Histological examination of A. forbesi tissues affected with SSWD showed cuticle loss, edema, and vacuolation of cells in the epidermis but little to no evidence of pathology caused by bacterial agents. Inclusion bodies were noted in two of the stars sampled.Challenge experiments by cohabitation and immersion in infected water suggest that the cause of SSWD is viral in nature, since filtration (0.22 µm) of water from tanks with SSWD does not diminish the transmission and progression of the disease. Death of challenged sea stars occurred 7-10 days after exposure to infected water or sea stars. Of the 48 stars tested by qPCR, 29 (60 %) have tested positive for the SSaDV VP1 gene.These stars represent wild-collected sea stars from all geographical regions (South Carolina to Maine), as well as stars exposed to infected stars or water from affected tanks. However, a clear association SSaDV with SSWD in A. forbesi form the East Coast of the US was not found in this study. Understanding the potential cause of this disease is a first step towards management and prevention of wide spread outbreaks.