Scientists have identified a contagious cancer in a catfish, making it only the fourth transmissible cancer known to science. These diseases are exceptionally rare because they do not spread like ordinary cancers. Instead, the cancer cells themselves pass between animals and continue growing in a new host.
The finding puts catfish alongside a very short list of species known to carry these unusual cancer lineages. The other known examples are found in dogs, Tasmanian devils and shellfish, according to the report. That makes the catfish case significant not only for fish biology, but also for the broader study of how cancer can evolve and survive across multiple animals.
Researchers describe transmissible cancers as contagious cell lineages, a category that stands apart from the better-known cancers that arise independently in each individual. In dogs, devils and shellfish, these diseases have already shown that cancer can sometimes act almost like a spreading biological entity rather than a one-off illness in a single animal.
The new catfish discovery expands that picture and suggests scientists still have more to learn about where transmissible cancers can appear in nature. With only four known cases so far, each new example offers a rare chance to understand how these cancers spread, persist and affect wildlife populations.
