Scientists Discover the First Contagious Cancer in a Freshwater Animal

Researchers identified a contagious melanoma spreading between brown bullhead catfish in Lake Memphremagog and nearby waters.

Genetic analysis showed the tumors are more closely related to each other than to their host fish, confirming a clonally transmissible cancer.

It is the first known transmissible cancer in a freshwater animal, with cases now found in Vermont, New England, and Canada.