{"id":716,"date":"2026-07-23T15:20:00","date_gmt":"2026-07-23T06:20:00","guid":{"rendered":"https:\/\/onepress.co.kr\/index.php\/briefing\/2026-07-23-brown-bullhead-transmissible-cancer-en\/"},"modified":"2026-07-23T15:20:00","modified_gmt":"2026-07-23T06:20:00","slug":"2026-07-23-brown-bullhead-transmissible-cancer-en","status":"publish","type":"briefing","link":"https:\/\/onepress.co.kr\/index.php\/briefing\/2026-07-23-brown-bullhead-transmissible-cancer-en\/","title":{"rendered":"A transmissible cancer has been identified in freshwater fish for the first time"},"content":{"rendered":"

2026-07-23 15:20 KST<\/strong><\/p>\n

Nature published a paper on 22 July 2026 identifying dark skin lesions in brown bullhead catfish as a natural transmissible cancer that moves between fish. The key point is that cancer cells themselves appear to have changed hosts in a fish species and freshwater setting for the first known time, not that this is a human infection risk.<\/p>\n

What Was Found<\/h2>\n

The researchers analysed black skin lesions seen in brown bullhead catfish from Lake Memphremagog, which spans Vermont and Quebec. The Nature paper says the lesions are not separate cancers arising independently in each fish, but a clonal transmissible cancer lineage that has moved between individuals. The paper frames it as the fourth documented type of naturally occurring transmissible cancer in animals and the first known occurrence in fish and a freshwater aquatic setting.<\/p>\n

What The Evidence Shows<\/h2>\n

The evidence comes from whole-genome sequencing of tumour tissue and matched non-tumour host tissue. Tumour mitochondrial and nuclear genomes were more closely related to one another than to their host fish, and hundreds of thousands of variants were shared among tumour samples but absent from host tissue. Earlier sampling in Lake Memphremagog had found lesions in 23-37% of sampled brown bullheads between 2014 and 2017.<\/p>\n

\"Freshwater
Produced image: ONEPRESS illustrates brown bullhead catfish lesions and a cancer-cell lineage concept. It is not a field photograph and does not imply human infection.<\/figcaption><\/figure>\n

Why It Changes The Question<\/h2>\n

Naturally transmissible cancers were already known in dogs, Tasmanian devils, and several bivalve species, but not in fish. This case shows that, under some conditions, cancer cells can behave more like a parasite moving through a wildlife population than a disease confined to one body. It gives researchers a new way to study wildlife disease, immune escape by tumours, and how water quality or habitat stress might shape cancer evolution.<\/p>\n

What Is Still Unknown<\/h2>\n

The route of transmission is not settled. UVM says researchers are examining possibilities such as close contact during spawning, the bottom-dwelling behaviour of the fish, sediment exposure, pollutants, and naturally occurring arsenic. Long-term effects on fish populations are also unknown. The important limit is that this does not mean cancer is infecting people; the researchers describe no known risk to humans.<\/p>\n

What To Check Next<\/h2>\n

The next checks are whether the same cancer lineage is present in more lakes and rivers, where it originated, and which conditions make transmission easier. Readers should use the Nature paper for genomic evidence and sampling scope, and the UVM release for field context, human-risk framing, and the unresolved transmission questions.<\/p>\n

Official sources<\/h2>\n

Nature paper: publication date, genomic evidence, and first fish\/freshwater scope<\/a><\/p>\n

UVM release: field range, human-risk framing, and remaining questions<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Nature published a paper on 22 July 2026 identifying dark skin lesions in brown bullhead catfish as a natural transmissible cancer that moves between fish. The key point is that cancer cells themselves appear to have changed hosts in a fish species and freshwater setting for the first known time, not that this is a human infection risk.<\/p>\n","protected":false},"featured_media":0,"template":"","meta":[],"class_list":["post-716","briefing","type-briefing","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/briefing\/716","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/briefing"}],"about":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/types\/briefing"}],"wp:attachment":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/media?parent=716"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}