Scientists Discover Cause of Sea Star Wasting Disease That Plagued Oregon Coast for a Decade

Published 08/07/25 at 7:05 a.m.
By Oregon Coast Beach Connection Staff

(Newport, Oregon) - After more than a decade of mystery surrounding one of the ocean’s most devastating wildlife epidemics, researchers have identified the cause of sea star wasting disease (SSWD), which has killed billions of sea stars along the Pacific coast from Alaska to Mexico. Starting in 2013 and 2014, it left visually disturbing remnants: gelatinous bulks that were unidentifiable littered the seafloor. (Photo Oregon Coast Aquarium)

Along the Oregon coast, it had been devastating, although now the region is seeing some recovery.

Published this week in Nature Ecology & Evolution, the study reveals that the disease is triggered by a strain of the bacterium Vibrio pectenicida - a microbe known for its destructive impact on marine life and human health. It is related to one that can cause cholera.

The discovery follows a rigorous four-year investigation led by scientists from the Hakai Institute, University of British Columbia, and University of Washington, in collaboration with The Nature Conservancy, the Tula Foundation, the U.S. Geological Survey, and Washington Department of Fish and Wildlife.

SSWD is considered the largest marine epidemic ever documented in the wild, affecting more than 20 species of sea stars. Among the hardest hit is the sunflower sea star (Pycnopodia helianthoides), a massive predator with up to 24 arms and a diameter rivaling a bicycle tire. Over 90 percent of the species has vanished in the past decade.

The disease deals a blow to ocean ecosystems, including the Oregon coast. Loosing sunflower sea stars has a cascading effect: these sea stars play a critical role in maintaining kelp forests by preying on sea urchins, which otherwise overgraze kelp beds. Kelp forests support thousands of marine species and contribute significantly to local economies through fisheries, tourism, and recreation.

The newly identified strain, Vibrio pectenicida FHCF-3, initiates a rapid and lethal infection in sea stars. The disease begins with external lesions and progresses to tissue breakdown, often described as “melting,” within two weeks of exposure. Infected sea stars become contorted and may lose limbs before dying. After the limbs dissolve in what is a gruesome sight, death is almost always inevitable.

Photo Oregon Marine Reserves

How researchers discovered the pathogen is a rather fascinating ride. Scientists over and over tested healthy sea stars in comparison to those stricken. They initially explored viral causes, but ultimately found high concentrations of the bacterium in the sea stars’ coelomic fluid - their version of blood. The team now hopes the breakthrough will guide future recovery efforts, including captive breeding and reintroduction programs.

“This discovery will enable recovery efforts for sea stars and the ecosystems affected by their decline by facilitating culture-based experimental research and broad-scale screening for pathogen presence and abundance in the laboratory and field,” the scientists wrote in the paper.

In 2021, aquarists at Oregon Coast Aquarium - headed up by Tiffany Rudek - developed a reliable method of treating ill, injured, or stressed sea stars. For many of the stars under her care, the treatment was the difference between life and death.

Healthy sea star - Hatfield Marine Science Center

There is still no known cure. Now, however, these findings mark a turning point in understanding the epidemic and offer new hope for restoring balance to marine environments long disrupted by the disease.

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