Devil facial tumor disease

Devil facial tumour disease (DFTD) is an aggressive non-viral transmissible parasitic cancer among Tasmanian devils.

The first official case of DFTD was described in 1996 in Australia. In the subsequent decade the disease ravaged Tasmania's wild devils, with estimates of decline ranging from 20% to as much as 50% of the devil population, across over 65% of the state. Affected high-density populations suffer up to 100% mortality in 12–18 months. The disease has mainly been concentrated in Tasmania's eastern half. Visible signs of DFTD begin with lesions and lumps around the mouth. These develop into cancerous tumours that may spread from the face to the entire body. Devils usually die within six months from organ failure, secondary infection, or metabolic starvation as the tumours interfere with feeding. As of 2010, 80% of population is infected, and only 0.1% is not affected. DFTD affects males and females equally. As of 2010, the population had been reduced by 70% (from 1996 census data), and if a cure is not found, a prediction has been made that the species will become extinct by 2035.

The most plausible route of transmission is through biting, particularly when canine teeth come into direct contact with the diseased cells. Other modes of transmission that cannot be discounted, yet haven't been conclusively proven, are the ingesting of an infected carcass and the sharing of food, both of which involve an allogeneic transfer of cells between unrelated individuals.. The cancer seems to infect the fittest devil individuals, which are socially dominant. Animals that eventually become infected survive at a higher rate and reproduce more before dying of the disease than devils that don’t get the cancer.

As of 2010, six females had been reported to have been found with partial immunity to DTF, and breeding in captivity was begun in an attempt to save the population.

DFTD tumours are "large, solid, soft tissue masses usually with flattened, centrally ulcerated, and surfaces", which are "typically multicentric, appearing first in the oral, face, or neck regions", and are " to nodular aggregates of round to spindle-shaped cells, often within a pseudocapsule and divided into lobules by delicate fibrous septae". The disease is described as being aggressive, locally. Tumours can cover the eyes.

As Iain O'Neill notes, it also presents a "high rate of regional lymph node involvement and systemic metastasis"; of the avenues by which the cancer can spread systemically, metastasis to the lungs, spleen, and heart are observed, as is secondary "intracranial involvement". O'Neill also notes that "organ involvement and superimposed infection may... contribute to mortality." Moreover, growth of large tumours impedes feeding, and starvation is another cause of death in affected devils.

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