The facial tumours that have decimated the Tasmanian Devil population are infectious and derive from a single animal, according to research published in Nature (http://www.nature.com, 2 February 2006).

In the past 10 years the population of these carnivorous marsupials has decreased from 140,000 to 80,000 because of a facial tumour that causes starvation. The new research proposes that it is the animals' vicious behaviour that is to blame. “Devils jaw wrestle and bite each other a lot...and bits of tumour break off one devil and stick in the wounds of another” said the study's author, Anne-Marie Pearse (http://news.bbc.co.uk, 2 February 2006). She added “It occurred to me that there didn't necessarily have to be a virus if the [cancer] cells themselves could be transmitted” (http://www.sciencenews.org, 2 February 2006).

The evidence that the tumours are infectious and derive from a single source came from examining karyotypes. The authors found exactly the same complex set of chromosomal rearrangements in the tumours of all 11 animals that they studied. In addition, one animal had a chromosomal rearrangement in its normal cells that was not found in its tumour. This identical tumour karyotype, found at all stages of tumour development and in all individuals, strongly supports the infectious theory.

It is thought that the low genetic diversity of the devils is the reason that the immune system does not kill the foreign cancer cells. A similar phenomenon has been observed when cancer cells are inadvertently transmitted with donated organs between closely related individuals.

A cull of infected animals is now thought to be the best way to proceed. “This is an incredibly urgent problem” said Ian Campbell, the Australian Environment Minister, announcing increased funding (http://www.abc.net.au, 7 February 2006).