OCEANS - Cause of Epidemic Starfish Deaths Found

"Finding the culprit virus in starfish deaths, researchers look for environmental causes" PBS NewsHour 11/18/2014

GWEN IFILL (NewsHour):  For the past year-and-a-half, scientists have been trying to figure out what’s behind a mysterious disease that’s led to the death of millions of starfish.

Now they have figured out the culprit, a virus.   Sea star wasting syndrome has affected more than 20 species of West Coast starfish.   First detected in Washington State last year, it’s since spread, decimating populations from Mexico all the way to Alaska.

This story comes from Katie Campbell at KCTS9 in Seattle.  She reports for the public media project EarthFix.

KATIE CAMPBELL, KCTS9:  After months of research, scientists have identified the pathogen at the heart of the starfish wasting disease.   They say it’s different from all other known viruses infected marine organisms.  They have dubbed it sea star associated densovirus.

IAN HEWSON, Cornell University:  When you look on a scale of hundreds and hundreds of animals, as we did, it’s very clear that the virus is associated with symptomatic sea stars.

KATIE CAMPBELL:  Ian Hewson is a microbiologist at Cornell University.   He’s the lead author of the study.  And he says it’s rare to figure out what causes marine diseases.

IAN HEWSON:  In every drop of seawater, there’s 10 million viruses that basically we have had to sort through to try and find the virus that is responsible for this disease.

KATIE CAMPBELL:  Researchers collected tissue samples and analyzed them for all possible pathogens.  Once they had identified the leading candidate, they tested it by injecting the densovirus into healthy starfish in an aquarium.  Then they watched to see if the disease took hold.

IAN HEWSON:  When we inoculated them, they died within about a week to 14 days, whereas controls, which had received sort of viruses that had been destroyed by heat, did not become sick.   They remained healthy for — for weeks.

KATIE CAMPBELL:  What’s strange, Hewson says, is that West Coast starfish have been living with the virus for decades.   Researchers detected the densovirus in preserved starfish specimens from as far back as the 1940s.

IAN HEWSON:  It’s probably been sort of smoldering sort of at a low level for a very long time, and then eventually it becomes sort of an epidemic.

Something seems to have been the trigger to make this from some sort of benign infection into something that’s really widespread and affecting so many different species.

KATIE CAMPBELL:  Now that scientists have identified the virus, the next step for Hewson’s team is investigating what environmental factors might make starfish more susceptible to it.