Third example of transmissible malignancy poses no threat to people
Michael J. Metzger
A leukemia-like disease in soft-shell clams is a contagious cancer that spreads from clam to clam, a new study finds.
The disease probably originated in a single soft-shelled clam at least 40 years ago, researchers report April 9 in Cell. Cancer cells somehow migrated to other clams and infected them, eventually spreading the disease up and down the eastern North American seashore from Canada’s Prince Edward Island to Chesapeake Bay.
It is not clear how the disease moves or whether the cancer cells can infect other mollusks. What’s certain is that the disease is not dangerous to people. “It’s only a shellfish health issue. It’s not a human health issue,” says Bruce Barber, an invertebrate pathologist at Eckerd College in St. Petersburg, Fla.
Only two other transmissible cancers have ever been described: a nonfatal venereal tumor in dogs and a facial tumor that