THE facial tumour disease that has wiped out nearly one-third of Tasmanian devils since the mid-1990s might be spreading through the transfer of cancerous cells between the animals during physical contact.
鈥淚t鈥檚 still just a hypothesis, but we think the cells themselves might be acting as an infectious agent,鈥� says Stephen Pyecroft, a veterinary pathologist and head of the Devil Facial Tumour Disease project in Tasmania.
Pyecroft鈥檚 team tested 81 diseased animals from all over Tasmania and found that their tumours were all essentially the same. They develop in neuroendocrine tissue and affect the animal鈥檚 mouth, head or neck regions. In one in five cases the aggressive cells spread to other parts of the body. The researchers don鈥檛 yet know if the animals mount any kind of immune response, but if they do, it is not strong enough to beat the disease. 鈥淥nce a devil develops a tumour it seems to be a one-way trip,鈥� Pyecroft says.
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The cause of the disease is still not entirely clear. A virus has not been ruled out, but no viral particles have been found in the tumours. However, the pattern of genetic material in the tumour suggests that it could be an 鈥渁llograft鈥� disease, transmitted by direct transfer of tumour cells during fighting and biting. The only other known example of such a disease is a venereal sarcoma that is spread between dogs during mating.
鈥淯naffected wild populations are being isolated where possible, and some healthy devils are being captured for breeding鈥�
The researchers have also sequenced the devil鈥檚 genome and identified a genetic marker for the tumour. Such knowledge will be vital for the development of any vaccine, though it will not be enough on its own. 鈥淲e need an awful lot more information before we get to that point,鈥� Pyecroft says. In the meantime, unaffected wild populations are being isolated where possible, and some healthy devils are being captured for monitoring and captive breeding.
Pyecroft鈥檚 team presented the work at the Wildlife Disease Association鈥檚 international conference in Cairns, Queensland, Australia, last week.
