The dirt on DFTD

The Tasmanian devil has suffered a dramatic population decline in recent years due to devil facial tumour disease (DFTD), an infectious cancer transmitted through biting. The low genetic diversity in Tasmanian devils has compounded the problem, and the recent discovery that the tumour itself is rapidly evolving has amplified concerns for the medium-term survival of this unique and iconic Australian species.

DFTD is one of the only cancers known to spread as a contagious disease. The cancer is spread from devil to devil primarily through biting. Transmitted tumour cells are not rejected by the recipient animal’s immune system. Due to the extremely close genetic kinship within the entire population, infected devils are veritable ‘universal organ donors’ to one another, passing on tumour cells during fights associated with feeding, territoriality and mating, that are then able to establish themselves in the opponent. In this manner, DFTD tumours have been referred to as parasitic. In addition to the spreading of the disease during fighting, it is possible that cannibalisation of sick or freshly deceased devils, as well as sexual encounters may account for dispersing the deadly ‘parasite’.

Advanced state of DFTD

Advanced state of DFTD

Once a devil is infected, signs of the disease appear in the mouth within a few short months, usually in the form of small lesions or pimple-like lumps. These small blemishes quickly develop into large tumours that grossly distort the face and neck (and sometimes other parts of the body). The devils soon find it difficult to eat and drink, leading to death from starvation, dehydration and the breakdown of body functions, usually within three months of the initial appearance of tumours. In the later stages of the illness the cancer typically metastasizes to vital organs, including the lungs and brain.

Infectious DFTD cells first derived from the body cells of a healthy Tasmanian devil in 1996 or perhaps a year or two earlier. As such, the tumour cells can only survive within Tasmanian devils. No other species, not even the devil’s closest kin – the quolls and other Dasyuridae species (marsupial predators) are capable of ‘hosting’ Tasmanian devil cells of any type, because their own immune system would immediately recognise the tumour cells as ‘non-self’ and destroy them.

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