Sea star wasting disease (SSWD) has devastated starfish populations along North America’s Pacific coast, pushing several species to the brink of extinction. Now, scientists have finally identified the culprit — Vibrio pectenicida, a marine bacterium also known for infecting scallops. This groundbreaking discovery offers new hope for saving these essential marine creatures.
A Marine Epidemic of Unprecedented Scale
First detected in 2013, SSWD rapidly spread from Alaska’s cold waters to Mexico’s warmer seas, infecting more than 20 species of starfish.
The disease is as gruesome as it is deadly: infected sea stars develop white lesions, lose the ability to move, and ultimately shed arms that crawl independently before their bodies dissolve into mush.
The sunflower sea star (Pycnopodia helianthoides) — a keystone predator in Pacific ecosystems — has been hit hardest, losing over 90% of its population in less than a decade. It is now listed as Critically Endangered.
Why Sea Star Wasting Disease Matters for Ocean Ecosystems
The disappearance of sea stars has triggered cascading ecological effects.
Without sunflower sea stars controlling their numbers, sea urchin populations explode, leading to the destruction of kelp forests.
This loss threatens countless marine species and affects coastal communities that depend on healthy kelp ecosystems for fisheries, tourism, and shoreline protection.
The Search for the Cause
For years, scientists debated whether a virus, environmental stress, or another factor caused SSWD.
The new study, published in Nature Ecology & Evolution (2025), used controlled laboratory experiments on sunflower sea stars to identify the true culprit: Vibrio pectenicida.
Researchers observed that when healthy sea stars were exposed to infected tissue, 92% died within days. However, if the tissue was heat-treated or filtered, the disease did not occur — strong evidence that a living microbe was responsible.
Analysis of starfish “blood” (coelomic fluid) revealed one striking difference between healthy and diseased individuals: the presence of Vibrio bacteria.
When the bacteria were isolated, grown in pure culture, and injected into healthy starfish, the animals developed the same wasting symptoms and died, confirming Vibrio pectenicida as a causative agent.
Climate Change Could Make the Epidemic Worse
The disease spreads more rapidly in warmer waters, meaning climate change could intensify future outbreaks. Vibrio bacteria are known to produce toxins, and researchers suspect these toxins may trigger the tissue breakdown seen in SSWD.
Understanding how the bacteria operate — and why warming seas accelerate the disease — will be essential for developing prevention and treatment strategies.
What’s Next for Conservation Efforts?
While identifying the pathogen is a major scientific breakthrough, controlling SSWD in the open ocean remains challenging.
Quarantining or treating wild populations in a vast, three-dimensional marine environment is extremely difficult.
Still, this discovery allows scientists to develop early detection tools for monitoring outbreaks and potentially breeding or restoring disease-resistant sea stars in the future.
Key Facts About Sea Star Wasting Disease
- First recorded outbreak: 2013, Pacific Coast of North America
- Species affected: Over 20, including sunflower sea stars
- Mortality rate: Up to 90% in some species
- Cause: Vibrio pectenicida bacterium
- Ecosystem impact: Loss of kelp forests due to unchecked sea urchin populations
- Future risk: Higher in warming ocean waters
Source:
Prentice, M. B., et al. (2025). Vibrio pectenicida strain FHCF-3 is a causative agent of sea star wasting disease. Nature Ecology & Evolution. DOI: 10.1038/s41559-025-02797-2