Scientists Just Discovered A Contagious Cancer In A Catfish, The Fourth Known To Science. Meet The Other Three - Forbes

What the report says

Forbes reported that biologists at the University of Vermont have identified a transmissible melanoma in brown bullhead catfish from Lake Memphremagog, on the Vermont-Quebec border. The finding, reported in Nature and highlighted by Forbes on July 27, makes the disease the fourth recognized type of contagious cancer known to science and the first documented in fish. The case traces public attention back to a 2012 catch in which a fish appeared to have dark, tar-like growths on its skin.

The report explains that transmissible cancers are rare because most tumors die with their hosts. In these unusual cases, however, the cancer cells themselves move between animals and persist as their own living cell line. Forbes describes the catfish melanoma alongside three previously known examples: canine transmissible venereal tumor in dogs, devil facial tumor disease in Tasmanian devils, and leukemia-like cancers in bivalves such as clams, mussels and cockles.

According to Forbes, the dog cancer is an ancient venereal tumor lineage that spread globally, while the Tasmanian devil disease is passed through biting and has sharply reduced wild devil populations. The article also notes that shellfish cancers can move through seawater and have arisen multiple times, including cases involving species jumps.

The discovery matters because it broadens the known range of animals affected by contagious cancers and may help researchers understand how cancer cells evade immune defenses, survive outside their original host, and adapt to new individuals. Forbes cautions that although only four broad kinds are recognized, the underlying number of independent transmissible cancer events is higher.