Biologists and data scientists have identified a transmissible melanoma spreading among brown bullhead catfish in Lake Memphremagog, which sits on the border of Vermont and Quebec. According to a study published Wednesday in the journal Nature, the cancer cells move from one fish to another, rather than being caused by external factors like ultraviolet radiation or environmental pollutants. Researchers first observed dark, ink-like lesions on approximately 25% of the catfish during a 2013 census.
Peter Emerson, a fish biologist with the Vermont Fish & Wildlife Department, stated that the lesions appear on the fins, skin, and eyes of the fish. Initial investigations into local pollution from the nearby Coventry Landfill found no evidence of toxins in the fishes' bodies that would account for the melanoma. Additionally, researchers found no evidence of a viral cause during their analysis.
The study authors suggest the cancer cells may escape one host and survive in the aquatic environment before infecting a new host. Julie Dragon, a data scientist at the University of Vermont, stated that studying how these cells invade new hosts and bypass immune systems could provide data on the mechanics of tumor metastasis. This discovery represents the first known instance of a transmissible cancer in a fish species.