Devil facial tumour disease



Devil facial tumour disease (DFTD) is a transmittable parasitic cancer in the Tasmanian Devil. The first "official case" was described in 1995, in Australia.

In the subsequent decade the disease ravaged Tasmania's wild devils, with estimates of decline ranging from 20% to as much as a 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 spread from the face to the entire body. The tumours interfere with feeding, and the affected animal may starve to death.

Characteristics of the cancer
Using cultures of the cancerous tissue to study the condition, researchers have identified the cancer as a neuroendocrine tumor, and all the cancer cells have identical chromosomal rearrangements. A virus was initially thought to be the cause of DFTD, but no evidence of such a virus could be detected in the cancer cells. Environmental toxins have also been suspected. The cancer cells themselves are an infective agent, with transmission of the disease occurring by biting, feeding on the same material, and aggressive mating. Final confirmation of this came when researcher Anne-Maree Pearse and colleagues found an infected animal that had a chromosomal abnormality in its non-tumourous cells that did not appear in its tumour cells, proving that the tumour cells could not have descended from the animal's own cells. Pearse believes that this may prove vital to the survival of the devils. Since June 2005, three females have been found that are partially resistant to DFTD.

Further research from the University of Sydney has shown that the infectious facial cancer may be able to spread because of vanishingly low genetic diversity in devil immune genes (MHC class I and II). The same genes are also found in the tumours, so the devil's immune system does not recognise the tumour cells as foreign.

Tasmanian Devil cells have 14 chromosomes, while the tumour cells contain 13. The DFTD cells have similar karyotype anomalies as cancer cells from canine transmissible venereal tumor, a cancer of dogs that is transmitted between animals by physical contact.

Preservation response
In response to the impact of DFTD on Tasmanian Devil populations, forty-seven Devils have been shipped to mainland Australian wildlife parks to attempt to preserve the genetic diversity of the species. The Tasman peninsula is being considered as a possible "clean area" with the single narrow access point controlled by physical barriers. The Tasmanian Department of Primary Industries and Water is experimenting on culling infected animals with some signs of success.