UNC Charlotte scientist helps oysters fight Dermo disease

Mar 20, 2009

Millions of oysters along the Eastern seaboard are dying from a parasitic disease called Dermo. It's the same problem that affected oysters off the Mexican coast in the 1940s. But those oysters adapted. Nature figured out a way to beat the disease. That's not the case for oysters off the Carolina coast. In this report, WFAE's Jen Nathan tells us how a UNC Charlotte researcher is using biotechnology in hopes of helping oysters fight back.

Like millions of oysters up and down the Eastern seaboard, oysters in the care of Inna Sokolova are infected with Dermo. It's disease that costs the commercial oyster industry millions of dollars each year. And it all starts with a parasite called Perkinsus marinus.

"It's a small microbe that gets inside the oyster cells and it starts destroying oyster tissues," Sokolova says from lab at UNC Charlotte. "So if the infection levels are very high, the oysters will become emaciated and eventually will die."

To make matters worse, every time an infected oyster dies, even more parasites are released into the ocean. That's how Dermo disease spreads. Some oysters, like the ones found in the Gulf of Mexico, have learned how to resist Dermo disease. Their immune cells simply engulf the parasite and destroy it. "Just kind of eat it up. It's called phagocytosis. They also produce reactive oxygen species - free radicals - that are very toxic so at high concentration they would kill the parasite. And if all else fails, then the next step for the immune cell would be to commit suicide."

Yes, commit suicide. It's called apoptosis and it's a way for sick animals to kill off infected cells to stop a disease from spreading inside the body. No one knows quite why, but Eastern oysters - like the ones that live in North Carolina - haven't adapted. They can't use apoptosis to fight off Dermo disease. So Inna Sokolova is trying to teach them how. "We're looking into some metals that are known to induce apoptosis."

Once Sokolova has healthy parasites, she uses them to infect oyster cells. Then she can begin the search for a metal that will force the sick oyster cells to commit suicide, so the rest of the oyster can live.

"Right now we are working with copper. We were also trying cadmium and zinc. The problem with cadmium is that it's a very toxic metal. So if you're thinking of the practical applications, you don't want to cure your oysters with cadmium because then you cannot sell them and you cannot consume them."

So far, copper diluted in salt water seems to be working. But Sokolova does not anticipate releasing copper into the ocean. That could wreak havoc on the ecosystem. Instead, her solution is aimed at North Carolina's cultured oyster farmers, who use mesh cages to grow oysters on top of the water.

"So you can take them out in a cage, give them a copper bath, and then put them back so that the remaining copper will be washed out so that there's nothing left by the time you're ready to sell them."

Leading biologists believe that oysters infected with Dermo disease are safe to eat. They say the parasites can't survive in the human body, much less infect it. But Dermo is still a major problem for the oyster industry. Infected oysters die at a young age - long before they're ready to be harvested. So Inna Sokolova's research could hold promising results for North Carolina's oyster farmers, as they try to grow disease-free oysters that can live long enough to be eaten.