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.
“It’s still just a hypothesis, but we think the cells themselves might be acting as an infectious agent,” says Stephen Pyecroft, a veterinary pathologist and head of the Devil Facial Tumour Disease project in Tasmania.
Pyecroft’s 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’s mouth, head or neck regions. In one in five cases the aggressive cells spread to other parts of the body. The researchers don’t yet know if the animals mount any kind of immune response, but if they do, it is not strong enough to beat the disease. “Once a devil develops a tumour it seems to be a one-way trip,” 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 “allograft” 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.
“Unaffected wild populations are being isolated where possible, and some healthy devils are being captured for breeding”
The researchers have also sequenced the devil’s 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. “We need an awful lot more information before we get to that point,” 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’s team presented the work at the Wildlife Disease Association’s international conference in Cairns, Queensland, Australia, last week.
