Sea Star Wasting Disease
(sea star affected by sea star wasting disease)
Sea star wasting disease, otherwise known as sea star wasting syndrome, is a disease that occurs sporadically within populations of sea stars and other echinoderms, causing mass deaths among populations affected. The species of sea stars most affected by SSWD are sunflower stars, giant pink stars, morning sun stars, mottled stars, and purple stars.
There have historically been three significant sea star plagues associated with the sea star wasting disease. The first was the 1972 plague, where huge populations of the Asterias rubens sea stars quite literally disintegrated in the east coast of the United States. Just 6 years later, the 1978 plague struck, destroying large numbers of Heliaster kubiniji sea stars in the Gulf of California, with the Heliaster sea stars even going extinct in many areas of the gulf. The most recent plague was that of 2013, where numerous species of sea stars succumbed to the disease in the east coast, coast of British Columbia, southern California, and more.
Although nothing is confirmed about sea star wasting disease, scientists have identified a few recurring symptoms from the past waves of plagues. The first symptoms were generally observed to be a sea star’s refusal to ingest food accompanied by weeks of listlessness. Soon after, white lesions would form on a sea star, the tissue around the aforementioned white lesions would decay, and the sea star would go limp due to the failure of the water vascular system. In the final stages of the disease, the sea star loses its ability to grab onto substrate, body structures disassemble, arms fall off, and the sea star would eventually disintegrate into a dead, white, mushy blob.
As mentioned above, nothing is confirmed about the sea star wasting disease due to the lack of knowledge, including causes. However, through numerous case studies, scientists have hypothesized a few possible causes for the disease. One possible cause of the disease could be a pathogenic virus, bacteria, or fungus, as identified in some instances of SSWD. Additionally, oxygen depletion, low salinity levels caused by freshwater runoff, and rising ocean temperatures have also been linked to SSWD, transitively pointing to global warming as a possible root of the problem. However, the strongest case to date is that SSWD is caused by a sea star-associated densovirus (SSaDV), a small microorganism that can be transmitted between sea stars, spreading the disease. The abundance of this densovirus was found to be much greater in sea stars affected by SSWD in comparison to healthy sea stars.
If you can see a theme here, there is no proven treatment to SSWD as well. However, one treatment that proved to be effective in the diseased sea stars of Point Defiance Zoo were antibiotics. Additionally, there is a small amount of research that shows that a single mutation in elongation factor 1-alpha locus of Pisaster ochraceus led to much lower death counts for SSWD affected sea stars.
Photo credit: https://marine.ucsc.edu/data-products/sea-star-wasting/