Over a dozen separate transmissible cancer events have now been recorded (Image: Getty)
Scientists have raised the alarm after uncovering a terrifying, contagious “flesh-eating” cancer spreading through wild populations – making it only the fourth known transmissible cancer in recorded history. The horror discovery, published in the journal Nature, marks the first time an infectious cancer has ever been detected in fish.
Biologists at the University of Vermont confirmed that a black, tar-like melanoma found on brown bullhead catfish from the Lake Memphremagog region on the US-Canada border is actively passing from fish to fish. While traditional cancers die alongside their host, these horrific mutant cell lines break free, multiplying continuously as an infectious parasite. Worryingly, scientists have warned that transmissible cancers are likely far more common in nature than previously believed, overcoming host immune systems and wreaking havoc across entire ecosystems.
A black, tar-like melanoma on brown bullhead catfish is spreading from fish to fish (Image: -)
First spotted when anglers pulled deformed fish with tar-like growths from the Vermont-Quebec border, the fish have now been fully sequenced, confirming every scientist’s worst nightmare – the black lesions are actually contagious tumour cells passing freely through the water from one catfish to another.
Researchers have warned that this is the first marine vertebrate discovered to harbour such a disease, raising fears about how easily waterborne tumours can infect aquatic species.
Perhaps the most terrifying example of a transmissible cancer is Devil Facial Tumour Disease (DFTD), which attacks Tasmanian devils. Spread through biting during fights over food and mates, the aggressive facial growths make it impossible for animals to eat, leading to starvation.
The disease, which has a nearly 100% fatality rate, has decimated populations by 80 to 90% in the hardest-hit areas, leaving the iconic marsupial listed as endangered. Terrifyingly, scientists found the cancer has independently emerged twice in the species, disabling the host’s immune identification system to spread unchecked.
DFTD has a nearly 100% fatality rate and has decimated populations by 80 to 90% in the hardest-hit areas (Image: Getty)
The initial 1996 outbreak (DFT1), which originated from a female devil, swept across 90% of Tasmania and slaughtered an estimated 38,000 wild animals – prompting emergency mainland quarantine programs to save the species. The crisis deepened in 2014 when scientists discovered a second, completely distinct strain (DFT2). Originating independently from a male devil, this newer variant is currently confined to the D’Entrecasteaux Channel peninsula, making Tasmanian devils the only known species on Earth to spawn two separate transmissible cancers.
In coastal waters around the globe, shellfish like clams, mussels, and cockles are falling victim to a leukaemia-like cancer of the blood. Malignant cells multiply until they choke the animal’s internal fluid, causing total organ failure. Because these tumour cells float freely in seawater, healthy shellfish contract the deadly cancer simply by filtering water to feed.
Worse still, researchers have identified at least 10 separate instances where this cancer has mutated, with some strains jumping across entirely different species or hitchhiking across whole oceans aboard cargo ships.
The oldest known living cell line on Earth, CTVT, is a genital cancer that spreads between dogs during mating. Genomic tracking shows every active case on the planet today descends from a single, husky-like dog that lived in Asia up to 11,000 years ago. While the ancient host died thousands of years ago, its cancer cells survived by jumping from host to host. It went global 500 years ago via European trading ships and survives to this day by literally “stealing” healthy cellular energy structures (mitochondria) from the dogs it infects.
The total number of distinct transmissible cancer events is now at least 13 (Image: Getty)
The discovery of the catfish melanoma brings the total number of distinct transmissible cancer events in nature to at least 13, proving that cancer’s ability to hop between host bodies is an escalating ecological threat.
Speaking on the horrifying potential of these rogue cell lines, evolutionary geneticist Professor Andrew Storfer warned: “I don’t think these are as rare as we think.”
Scientists are now racing to study the Vermont catfish outbreak to understand how the cells survive in open water – and to determine whether other species could be next.
Dr Gareth Nye, lecturer of Biomedical Science at the University of Salford, told the Express: “There is absolutely no evidence that this or other contagious cancers can spread to humans as they are highly species-specific, and our immune system is designed to destroy foreign cells. Additionally, there have been no truly contagious cancers found in humans, unlike those found in animals.
“However, relevant agencies generally advise against consuming any fish that displays obvious signs of severe disease, open sores, or tumours, regardless of cause.
“This may even be of huge benefit to humans as researchers are studying cancer behaviours like this to fully understand how and why cancers develop and grow. It may even lead to new avenues for therapy.”
