First-known freshwater contagious cancer spreading among catfish in this lake

Key Points:

• Researchers have discovered the first-ever transmissible cancer spreading among brown bullhead catfish in the freshwater Lake Memphremagog, affecting 23 to 37% of the population with malignant melanomas.
• The cancer was identified after high rates of raised black lesions were observed since 2012, prompting genomic analyses that showed tumor genomes in affected fish shared a single clonal origin, indicating transmissibility.
• This transmissible cancer is the first known case in fish and freshwater species, joining only a few other known transmissible cancers found in dogs, Tasmanian devils, and certain bivalves.
• Scientists are uncertain how the cancer spreads but suggest that factors related to reproduction or aging may play a role, with ongoing research aimed at understanding its evolution and impact on the catfish population.
• The discovery raises concerns due to Lake Memphremagog's role as a drinking water source for 175,000 people, and initial hypotheses linked the cancer's emergence to environmental changes following Tropical Storm Irene's flooding in 2011.