A horrible cancer is spreading rapidly between Tasmanian devils.
An ANU PhD student wants to find out why.

Its fearsome guttural growls and voracious scavenging led the earliest European settlers in Tasmania to brand it ‘the devil’. The name stuck, and it came to serve the Tasmanian devil well by endearing curious tourists and even inspiring a cartoon character.

Now an unsightly and deadly disease that’s infecting the devil population has taken on the qualities of a demon, and it’s threatening to make the devil extinct.
Since Devil Facial Tumour Disease was first recorded in 1996 and the speed of its transmission realised, there has been a rush to learn more about the disease and, ultimately, to find a treatment or cure.

ANU PhD student Hannah Bender is one scientist taking part in an Australian Research Council Linkage grant with the Tasmanian Department of Primary Industries and Water (DPIW) to test the theory that the disease is transmitted through devil-to-devil contact, such as biting, and not by a virus or bacteria as previously thought. The current theory is that the cancer cells themselves transmit the disease. It means that a single cell passed from an infected devil to a healthy devil has all the genetic data to begin to cause the growth of the deadly tumour.

The ‘allograft hypothesis’, as it is known, was first proposed by Anne-Maree Pearse, a DPIW cytogeneticist and co-investigator of the Linkage grant team, in Nature in February 2006.

Pearse discovered that the chromosomes from tumour cells were highly abnormal but, more importantly, that the chromosome changes were identical in tumours from different animals. The complexity of the chromosome rearrangements suggested that the tumour was being transmitted by a rogue cell.

Bender, who is conducting her research in the Comparative Genomics Group at the Research School of Biological Sciences, is focusing on identifying the chromosome rearrangements or breakpoints that could have led to the development of the disease.

She is using a technique called ‘chromosome painting’ to test the allograft hypothesis, deploying advanced cytogenetic techniques that compare the chromosomes from healthy devils to those infected with the disease.

The fatal disease has been identified at 60 sites in Tasmania, covering 59 per cent of the Apple Isle at the end of 2006, according to the DPIW.

The tumour predominantly leads to deformity on the head, mouth and neck and also spreads to other internal organs in 65 per cent of cases. It initially appears as small nodules which progress to large, ulcerated lesions, and on average the devils die within six months of the first lesions appearing.

The proportion of animals displaying signs of the disease at some of the 60 sites has reached up to 83 per cent of trapped adults. Unless a treatment can be found soon, the cancer threatens to make devils extinct in the wild.

After graduating with a degree in veterinary science, Bender began her PhD research project by going to Tasmania for four months to collect 11 tumour samples from infected wild devils. She is comparing these with 11 blood samples taken from healthy devils.

“It was good to be able to get out into the field with the people who are part of the project, to see all the work they’re doing to try and understand this disease,” Bender says. “But it was also quite stressful at times, seeing the animals that were infected.”

Chromosome painting takes a single strand of DNA, in this case from a healthy devil, which is ‘painted’ with fluorescent dye that attaches to the exact part of the chromosome that matches that of an infected devil.

When the painted DNA from the disease-free devil is hybridised to the chromosomes of its diseased counterpart, the complementary areas of the chromosome “light up”, according to Dr Amber Alsop, one of Bender’s supervisors. The stained areas indicate which parts of the normal chromosomes have been rearranged in the tumour chromosomes. This provides a starting point for indicating which regions of the Tassie devil genome may be involved in the cancer’s development.

It is hoped that this research will at the very least provide a definitive conclusion on the allograft theory, providing a path for future research, and, at the most, lead to a diagnostic test or treatment.

“It’s a really horrible disease. It seems that an infected devil only has to bite another devil to pass on a cell, and that single cell has everything it needs to begin to grow and lead to tumours,” Alsop says. “How this system of transmission developed really is the focus of our work.”

“We hope that this research will also prove informative for our comparative studies of carcinogenesis and tumours in other species, including animals and humans,” Bender says.
The researchers must work quickly. Anecdotal reports from Tasmania are that the decline in the devil population, particularly in the state’s northeast where the disease was first recorded in 1996, is likely to affect the balance of native species versus exotics.

The devil’s carnivorous appetite and ferocious attitude are thought to have kept a lid on the fox and feral cat populations. With fewer devils preying on the carcasses of dead wildlife and stock, it’s feared that there will be more food available for foxes and cats and that the numbers of these exotic animals could increase.

With so much at stake, Bender hopes to contribute as much as she can to the research project.

“Doing the research on the Tasmanian devil is really exactly what I want to do. I never really wanted to be a clinic vet. It’s been great to be part of a bigger research project, within an even larger support movement for the devil, which hopefully, eventually, we can help.”

Devil Facial Tumor Disease

• Disease identified at 60 sites in the north and central east of Tasmania
  
• Proportion of devils with the disease at any one site has reached up to 83 per cent of trapped adults
  
• Sightings of wild devils declined by 41 per cent from 1992- 1995 to 2002-2005
  
• Fatal within three to 12 months of first lesions appearing
  
• Nearly all devils die between two and three years of age
  
• Forty-seven healthy devils (29 adults and 18 imps) have been sent to mainland wildlife parks and institutions in an attempt to preserve the species (after quarantine periods)
  
• Western third of the Tasmanian land area currently remains disease-free
  

Some information for this article came from the Tasmanian Department of Primary Industries and Water.

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ANU Reporter 
Autumn 2007