The cancer that behaves like a contagious parasite
In short: In Tasmania, a deadly disease is spreading not through viruses, but through physical contact. This aggressive cancer, known as DFTD, moves from one devil to another via bites, turning the species' own social aggression into a mechanism for its potential extinction.
Devil facial tumour disease (DFTD) is a rare, non-viral, clonally transmissible cancer. Unlike most cancers that arise independently within an individual, DFTD cells are genetically identical across different hosts, suggesting the disease originated from a single individual around 1986. This process, known as the Allograft Theory, allows the cancer to spread through biting, scratching, and even aggressive sexual activity. Researchers have identified the cancer as a neuroendocrine tumour, noting that its chromosomal rearrangements are strikingly similar to those found in the canine transmissible venereal tumour.
The disease manifests as ulcerating lumps around the mouth that can destroy the jawbone, interfere with feeding, and eventually metastasize to the lungs, spleen, and heart. For the Tasmanian devil (Sarcophilus harrisii), the impact has been catastrophic; the population declined by 80% to over 90% in less than two decades. The disease is almost universally fatal, with most affected individuals dying within six months due to organ failure or starvation. The disease primarily targets the fittest adult individuals, though it is notably rare in juveniles. While the disease has spread through much of the island, some isolated pockets in the far southwest remain free of the pathogen.
Two distinct strains currently exist. The primary strain, DFT1, was first described in 1996. A second, genetically distinct strain, DFT2, appeared around 2011 and is found in southern Tasmania. Interestingly, DFT2 is tetraploid—containing twice the genetic material of normal cells—and mutates approximately three times faster than DFT1. While researchers are testing vaccine candidates, the evolution of the cancer remains a significant challenge, as some believe disease eradication efforts may even act as a selective pressure favoring slower-growing tumours. To prevent total extinction, conservationists have established insurance populations, including a significant group of 500 animals in captivity as of 2012. Some efforts even involve relocating healthy devils to Maria Island to build a new, disease-free population.
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- Summary by Intellect · source: Devil facial tumour disease
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