Freshwater Catfish Harbor the World’s First Contagious Cancer
Researchers in Vermont found a contagious form of melanoma in brown bullhead catfish from Lake Memphremagog. Genomic analysis showed tumors shared hundreds of thousands of variants across fish that weren’t present in healthy tissue, indicating an infectious cancer—the first documented in fish and freshwater animals. Transmission details remain unclear (spawning or environmental factors like arsenic may play a role), and while not dangerous to humans, the cancer raises questions about immune evasion and cancer biology.