Contagious Cancer in Catfish Could Revolutionize How We Treat Human Cancer

Vermont biologists made a discovery that’s capturing the attention of cancer researchers across the globe. In Lake Memphremagog, a body of water straddling the Vermont-Quebec border, scientists found a contagious form of melanoma spreading rapidly through the catfish population. Since around 2013, the infection rate has climbed steadily. Today, approximately thirty percent of the lake’s catfish carry dark blotches of cancer on their skin, fins, gills, and sometimes even their eyes and mouths. What makes this discovery extraordinary is that the cancer cells are genetically identical clones that somehow transfer from one fish to another, likely during spawning season when catfish gather in clusters and scratch each other with their sharp spines.

This marks only the fifth documented case of transmissible cancer in animals worldwide, joining Tasmanian devils, certain dog populations, and some molluscs on that extremely rare list. Researchers used genome sequencing to confirm that the cancer cells were distinct from their host fish, proving the disease was being transmitted rather than developing naturally. What captivated scientists most is the implication for human cancer research. If they can understand how these catfish cancer cells escape from one host and successfully infect another, they might unlock the mystery of how human cancers metastasize and spread through the body. Such knowledge could fundamentally change cancer treatment and save countless lives. The fish appear able to survive with these tumors for extended periods, which also provides valuable insights into how cancer adapts and persists.

Researchers continue investigating environmental factors that may have triggered this outbreak, and some historians have noted that Henry David Thoreau may have observed this same melanoma in Massachusetts catfish over 150 years ago. The discoveries coming from Lake Memphremagog remind us that sometimes the most important answers to our biggest health challenges are waiting to be found in nature itself. What aspects of this story interest you most, and do you have thoughts on how we should approach studying environmental health in our own region?