Sea star wasting disease (SSWD) or starfish wasting syndrome is a disease of starfish and several other echinoderms that appears sporadically, causing mass mortality of those affected. The disease has affected over 20 species of sea stars, many of which are found on the western coast of North America. The disease seems to be associated with increased water temperatures in some locales, but not others. It starts with the emergence of lesions, followed by body fragmentation and death. As of 2025, more than 5 billion sea stars have been lost from the 2013 plague, resulting in a population decline of over 90% in some species. The decimated numbers of sea stars on the Pacific Northwest coast has led to major ecosystem imbalance, with rising sea urchin populations due to the lack of sea star predation, which uncontrollably feed on the local kelp forests. In 2014, it was suggested that the disease is associated with a single-stranded DNA virus now known as the sea star-associated densovirus (SSaDV), but this hypothesis was refuted by research in 2018 and 2020. In 2025, a study published in the journal Nature Ecology and Evolution showed that the bacterium Vibrio pectenicida strain FHCF-3 caused a SSWD-like condition in Pycnopodia helianthoides.
Symptoms Typically the first symptom of sea star wasting disease is refusal to accept food followed by listlessness for weeks and then white lesions that appear on the surface of the starfish and spread rapidly, followed by decay of tissue surrounding the lesions. Next the animal becomes limp as the water vascular system fails and it is no longer able to maintain its internal hydrostatic balance. The sea star loses its grip on the substrate. The body structure begins to break down, signs of stretching appear between the arms which may twist and fall off, and the animal dies. The arms may continue to crawl around for a while after being shed. Progression of these events can be rapid, leading to death within a few days. A deflated appearance can precede other morphological signs of the disease. All of these symptoms are also associated with ordinary attributes of unhealthy stars and can arise when an individual is stranded too high in the intertidal zone (for example) and simply desiccates. "True" wasting disease will be present in individuals that are found in suitable habitat, often in the midst of other individuals that might also be affected. The final result is a disintegrated, white, mushy blob, which no longer seems to be a sea star.
1972 plague The 1972 plague was the first notable case of Sea Star Wasting Disease. Scientists noticed a rapidly declining population of common starfish (Asterias rubens) occurring off the east coast of the United States. The symptoms were that the starfish became limp and lost limbs until finally melting into a white mucus-like paste.
1978 plague In 1978 large numbers of Heliaster kubiniji succumbed to a wasting disease in the Gulf of California. At the time, it was suspected that high water temperatures were a causal factor. This sea star became locally extinct in some parts of the gulf, and some populations had not recovered by the year 2000. Because this sea star was a top-level predator, its disappearance had profound effects on the ecosystem. In the Channel Islands off the coast of California, ten species of sea star were recorded as being affected as well as three species of sea urchins, two brittle stars and a sea cucumber, all of which experienced large population declines.
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