Tasmanian Devils, Extinction, and Infectious Cancer

14 Feb

We may be watching the last days of the wild Tasmanian Devil.

Since the 1990’s a new type of disease has been spreading throughout the island. A cancer, specifically, known as devil facial tumor disease. Cancer normally cannot spread beyond the original host, transmission to a new host should be rejected like a bad skin graft, but this one can. Only two other parasitic cancers are known, one called CTVT in dogs and a mosquito-transmitted sarcoma in hamsters.

This specific cancer, which likely originated in neuron-insulating Schwann cells, is spread by biting. Tasmanian devils (Sarcophilus harrisii) are notoriously aggressive and fighting is a key part of their social life, feeding habits, and sexual encounters. As they fight, cancer cells from the infected animal spread into open cuts on the healthy one. There the cancer takes root and grows. The tumors eventually become so large that the animal can no longer eat and slowly starves to death.

The disease is both virulent and aggressively severe. Since the 1990’s the population has dropped precipitously. In some areas only a tenth of the population remains. Extinction in the wild is likely across wide areas and isolated communities may end up being the only surviving wild populations. Conservation efforts are underway. Culling of sick individuals has been tried, to limited success. A paper in 2011 recommended the selection of a kind genetic ark, enough diverse healthy individuals to continue the species.

If nothing else, we can depend on captive populations to keep the devils from extinction.

Sources: Banfield et al (1965), Miller et al (2011), McCallum et al (2007), Murchison (2008)Pearse and Swift (2006)Wikipedia

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Posted by on February 14, 2012 in Natural History, Uncategorized


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