For months, scientists have been trying to figure out which pathogen is responsible for the terrible wasting disease that has been affecting millions of starfish along the Pacific coast of North America. Now, an international team of researchers says the mystery behind the plague has been solved. The scientists discuss their findings in a paper published Monday in the journal Proceedings of the National Academy of Sciences.
The scientists call the microbe behind the plague ‘sea star associated densovirus’ because it is unlike all other known viruses infecting marine organisms, according to a report by PBS.
“When you look on a scale of hundreds and hundreds of animals, which we did, it’s very clear that the virus is associated with symptomatic sea stars,” said lead author Ian Hewson, a microbiologist at Cornell University, in the PBS report.
It is not an easy task for researchers to identify which particular virus is responsible for diseases afflicting marine animals—a single drop of sea water contains some 10 million viruses.
“Basically, we’ve had to sort through to try to find the virus that is responsible for the disease,” Hewson said.
The scientists analyzed tissue samples from both sick and healthy starfish for all possible pathogens that could be the cause of the wasting disease. Then they sequenced DNA samples from those viruses and compared them to all other known viruses.
Once the team had identified a top candidate, they injected it into healthy starfish and watched to see if sickness resulted. It did.
“When we inoculated them they died within about a week to 14 days,” explained Hewson. “Whereas controls that had received viruses that had been destroyed by heat, did not become sick.”
As the team tried to determine how the densovirus arose, they found out that it has been lurking alongside Pacific coast starfish for at least 60 years. They detected the densovirus in specimens of starfish preserved in the 1940s.
Hewson said the densovirus probably had been “smoldering at a low level for a very long time.”
Researchers are still trying to determine what caused an apparently benign virus to change into what marine biologists think is the worst-ever disease outbreak affecting marine life.
The team is looking at ways starfish could develop resistance to the densovirus and also plans to continue investigating how environmental factors such as ocean acidification and global warming may have led to starfish becoming more susceptible to infection.