Pathogen in Pacific Coast Starfish Plague Identified

Pathogen in Pacific Coast Starfish Plague Identified

The pathogen causing the Pacific coast starfish plague has been identified. In a paper published by the Proceedings of the National Academy of Scientists, researchers have explained what is causing asteroid mass mortality off the west coast of North America.

For over a year, starfish have been mysteriously, inexplicably dying. Sea Star Wasting Syndrome has been devastating starfish populations in the Pacific Ocean. It has affected at least 20 species of starfish, leaving swathes of dead, limbless sea stars littering the ocean floor. Finally, marine biologists have found the culprit.

Sea Star deaths were first noticed in the Puget Sound of Washington State. It was soon discovered that the sickness had spread all along the coast as far south as Mexico and as far north as Alaska. Starfish were dying off in droves.

The starfish were completely degenerating. The first symptom of the disease is a curling of the legs. Then lesions and swelling appear. Next the asteroids lose the ability to coordinate their limbs and the legs begin to pull away from the central body, ripping the sea star apart. They end by literally disintegrating into mush, hence, the term Wasting Syndrome.

After months of research, scientists have finally identified the virus causing the Sea Star Wasting Syndrome. They say it is unlike any other marine pathogen and have named it the Sea Star associated Densovirus (SSaDV). With thousands of starfish to study, marine biologists are positive that SSaDV is responsible for the asteroid deaths. Ian Hewson, a microbiologist from Cornell University, was lead author of the study. He said there is no doubt that SSaDV is associated with symptomatic asteroids.

Some researchers in the field say it is astonishing that the biologists were able to positively identify the pathogen. According to Hewson, every drop of seawater contains 10 million viruses. Biologists collected and tested samples of dead animals looking for a common pathogen. Once they had a suspect, they tested their theory by injecting the virus into healthy asteroids. Those sea stars inoculated with SSaDV died within a week, verifying suspicions.

Strangely, asteroids have been living with this virus for decades and only within the past two years did mass numbers begin dying. Perhaps the pathogen needed to increase in population before it began causing death. Or, maybe something else in the environment triggered the virus to go from an annoyance to a mass murderer. The virus has been found in plankton, sediments and non-asteroid echinoderms, any or which may have provided the mechanism for transmission. Suddenly, SSaDV is causing a starfish pandemic.

The next step for Hewson’s team is investigating environmental factors that make asteroids more susceptible to SSaDV. Eradicating the virus or vaccinating the starfish would be a Herculean task, but fixing environmental conditions should be more within the realm of possibility.

Hewson reassures the public that mass viral outbreaks are a natural part of marine life cycles. There is every expectation that starfish populations will bounce back. Already, marine biologists are seeing record numbers of juvenile starfish in the Pacific coastal waters. Hewson says the sea stars have more to fear from ocean acidification and global warming than they do from a natural pathogen. Still, seeing huge numbers of beautiful creatures die from the virus is unsettling.

Scientists have identified the pathogen causing the Pacific starfish plague. They believe something in the environment has combined with SSaDV to make it more deadly to asteroids. Once they can identify the environmental factor, the marine biologists can act if necessary. It is likely that the virus will run its course and sea star populations will rebound on their own.

By: Rebecca Savastio

Sources:

PBS

LA Times

Ars Technica

Photo Credit: Creative Commons

 

 

 

 

 

 

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