Environment News

Contagious Cancer in Catfish

October 24 , 2026 15 hrs 0 min 14 0

Scientists from the University of Vermont reported the fourth known case of naturally transmissible cancer in animals, involving melanoma in brown bullhead catfish (Ameiurus nebulosus) from Lake Memphremagog.
The cancer cells originated in one fish and spread to other fish, where they formed tumours; about 30% of catfish sampled from the lake since 2013 had melanoma.
Genetic analysis showed major differences in mitochondrial DNA (mtDNA) between tumour and normal cells, supporting the spread of cancer cells from an outside fish.
Researchers suggest the cancer cells may spread through physical contact during spawning or the aquatic environment, entering new fish through the gills, skin or mouth.
Earlier transmissible cancers are known in dogs, Tasmanian devils and bivalve molluscs such as clams and mussels.