North American Clams Are Spreading a Contagious Cancer

The Atlantic waters off of the east coast of the US and Canada are home to a host of delicious clam species, from giant quahogs to elongated razors. But if you fancy a big bowl of soft-shell clams—a.k.a. steamers—then you might want get to the fish market sooner rather than later.

According to a recent Agence France Presse article, scientists have discovered an unusual type of leukemia that's spreading between soft-shell clam populations in North American waters. Researchers located the cancer in clams living offshore of New York, Maine, and Prince Edward Island in Canada, and have concluded that it's been killing "untold numbers" of the tasty bivalves.

The study on clam cancer was published in the most recent issue of the scientific journal Cell. Stephen Goff, its lead author, told AFP that the contagious nature of the leukemia is unusual for a cancer.

"We were pretty amazed," Goff said.

Normally, cancer begins when a cell in the afflicted organism's body mutates. But in the case of the disease affecting the steamers, Goff and fellow researchers found that the leukemia cells did not match the individual clams that were stricken. In other words, the tumors matched each other but not the host animal they were growing in.

"Astoundingly, the conclusion is that this is spreading as a tumor line from animal to animal and this is how each animal gets sick," Goff said.

According to the study's authors, it's likely that the cancer clone developed in one clam, and then began spreading to others, and may be "widespread" in the marine environment.

Previously, scientists had thought that contagious cancers were relatively rare: only two other forms are known, and affect Tasmanian devils (face tumors) and canines (venereal disease), respectively. After discovering the clam illness, researchers concluded that "horizontal transmission of cancer cells is more widespread in nature than previously supposed."

Although it's potentially depressing news for seafood lovers, clam leukemia might prove to be useful to the scientific community. Since the disease appears to easily move from one host to another, studying it might provide clues about cancer in humans, which moves from one part of the body to another.

"People are very keen to know what allows a cell to do this," Goff said.

So how does this news affect diners and home cooks? Rest assured: researchers say there's no danger of humans catching cancer by eating a diseased clam. So tonight could be a great night to bust out your biggest pot and cook up some steamers—while supplies last.