Researchers identify likely transmissible melanoma in wild brown bullhead catfish
A study published in Nature reports that melanoma cells appear to spread between brown bullhead catfish in Lake Memphremagog, marking the first known transmissible cancer in fish and in a freshwater environment.
Scientists studying brown bullhead catfish in Lake Memphremagog, which straddles Vermont and Quebec, found that between 23% and 37% of sampled fish carried melanoma lesions, a rate far higher than previously recorded. Whole-genome sequencing showed that tumor DNA from different fish was nearly identical and distinct from the host fish DNA, indicating that the cancer cells likely originated from a single lineage and were transmitted between individuals.
The researchers noted that the exact mechanism of transmission remains unknown, but suggested that close contact during spawning could facilitate the spread of cancer cells. While transmissible cancers have been documented in dogs, Tasmanian devils and certain bivalves, this is the first instance reported in a freshwater fish species.
"The cancer cells do not appear able to affect other species in the area, and there is no evidence that people can catch cancer from these fish or from the lake water," the study authors said.
Lake Memphremagog supplies drinking water to more than 175,000 residents, but scientists say there is no known risk of the catfish melanoma transmitting to humans. The discovery may provide new insights into how cancer cells evade immune defenses and propagate across hosts.