Wild Catfish Carry First Known Case of Transmissible Cancer, Study Finds

Researchers studying brown bullhead catfish from Lake Memphremagog found a high rate of melanoma and, using whole-genome sequencing, evidence that the tumors in multiple fish are from a single cancer cell lineage that appears to spread between fish, marking the first known transmissible cancer in a fish and in a freshwater setting. Transmission may occur during close contact such as spawning, though the exact route isn’t proven. There’s no evidence this cancer affects humans or other species, but the finding could help scientists understand how cancer cells evade the immune system and persist across hosts.