Overview
- A University of Vermont‑led study published July 22 found that skin tumors on brown bullhead catfish in Lake Memphremagog are a clonally transmissible melanoma, meaning the cancer cells themselves move between fish.
- Genomic comparisons show tumor cells from different infected fish are far more closely related to one another than to their hosts, which is the hallmark of a transmissible cancer lineage.
- Field samples taken in 2014–2017 showed the disease was common in the lake with malignant melanomas on roughly 23–37 percent of sampled fish, and the same cancer lineage has been detected in a few other regional ponds and lakes.
- Researchers have not identified a definite transmission route and are testing leading hypotheses such as direct transfer during dense spawning contact, transfer via pectoral‑fin spines, or environmental transfer through water or sediment.
- Scientists also found elevated arsenic in tumor tissue and a correlation with local soil arsenic levels but say causation is unproven, there is no evidence of human risk, and the finding offers a new model to study cancer evolution and immune evasion.