Hopes for a cure of the deadly facial tumour disease (DFTD) in Tasmanian Devils have grown with the breakthrough that scientists have discovered its genetic code. DFTD is a highly contagious mouth cancer unique to Tasmanian devils passed on during sex and fights. The tumour quickly spreads on the face and down to internal organs, killing the devil within nine weeks. The mysterious disease has threatened the species with extinction within 35 years. However the new discovery of the genetic composition allows scientists to develop a diagnostic test for it. The Australian and overseas-based research team hopes to be able to develop not just vaccines, but therapies as well.
University of Tasmania researchers earlier last year developed a pre-diagnostic test similar to a Prostate Specific Antigen (PSA) test in the detection of human prostate cancer but has not yet been scientifically validated. A diagnostic test builds on the earlier work and will be more conclusive. Scientist Greg Woods from the Hobart-based Menzies Research Institute said the identification of the nerve-protection called Schwann cells as the likely origin of DFTD was a significant step. "We are now much more confident in understanding what the tumour cell is and this will help in the development of treatments and strategies to combat this disease," he told The Australian.
DFTD is a new disease. Not a single case was found in any animal captured by wildlife biologists up to 1995. It was first diagnosed in 1996 when devils with large facial tumours started appearing. Small lumps around the mouth quickly develop into large tumours on the face and neck making it difficult for the animal to eat. If they don’t die first of starvation, the cancer kills the infected animal within nine weeks. By the end of 2009 DFTD had laid waste to 60 percent of the total devil population. In the north-east region, where signs of the disease were first reported, there has been a 95 percent decline of sightings of the animal in the decade from 1995 to 2005.
Scientists initially thought DFTD was a virus but realised it was a cancer after they compared the DNA from sick and healthy devils. They discovered that a single nerve cell gene from one devil created the disease cells and then spread to many other animals. Analyses of these cell genes and gene activity patterns indicated that the tumor cells most closely matched Schwann cells, a type of cell that forms a waxy sheath called myelin around nerve fibres.
The researchers say a protein called periaxin normally found only in Schwann cells is also present in devil facial tumor cells and might be a good diagnostic marker for the disease, the researchers report. They still don’t know how the cancerous Schwann cells became contagious in the first place. Katherine Belov, a geneticist at the University of Sydney, believes it may simply be a “freak of nature” that allowed the cancer to be stable and transmitted.
Whatever it was, its effects have been catastrophic among devil populations. In May 2009, the Australian Government raised the Tasmanian devil from “Vulnerable” to “Endangered” under national environmental law. Tasmania’s Threatened Species Act 1995 has also listed the devil as “Endangered” since May 2008. By the end of 2008, the disease had been confirmed at 64 locations, covering more than 60 percent of Tasmania. The Tasmanian government has launched a Save the Tasmanian Devil Program aimed at maintaining genetic diversity, maintaining healthy populations in the wild and managing the ecological impacts of reduced populations.
It is usually uncommon for wildlife diseases to lead directly to population extinction in the absence of other severe threats. But ominously, there had not been any evidence of a single recovery from the disease. There are fears that niches left vacant by the large carnivorous marsupial will be taken up by introduced species such as feral cats and foxes. If this occurs there could be a wider impact on Tasmania's unique wildlife. The new scientific findings represent the best hope to save the devil. It may take ten years to produce a vaccine against the disease but that will probably be enough time not only to save the animal from extinction but also avoid tipping the island into a major ecological collapse.