Devil Facial Tumour Disease (DFTD) is one of only three recorded cancers that can spread like a contagious disease. The cancer is passed from devil to devil through biting. The live tumour cells aren’t rejected by the animal’s immune system because of a lack of genetic diversity among Tasmanian devils.
For this reason, cases continue to occur in areas where the disease had not previously been recorded. As at February 2010, there has been a 80% decline in average sightings across Tasmania from 1992-95 to 2003-06. In the north-east region, where signs of the Tasmanian devil disease were first reported, there has been a 95% (approximately) decline of average spotlighting sightings from 1992-95 to 2002-05.
It is uncommon for wildlife diseases to lead directly to population extinction in the absence of other severe threats. But to date, there had been little evidence of population or individual resistance or recovery from the disease. One population in the Central Highlands does seem to be less susceptible to the disease. Research is being carried out to investigate why this may be the case.
Locating the western extent of Devil Facial Tumour disease
During September and October 2009, surveys were conducted in western Tasmania with the objective of locating the western extent of Tasmanian devil facial tumour disease (DFTD). Knowing the location of the disease ‘front' is essential to inform other management projects aimed at preserving the species in the long term, including the potential fencing off of disease free areas and the development of free range captive enclosures. Prior to these focused trips, there had been no intensive, focused trapping trips to find the location of the disease front.
Six teams surveyed sites between Burnie in the north and Kelly basin in the south. A roving veterinary team responded to reports of potential disease in captured animals, and collected biopsies and blood samples for confirmation of the disease. As the principle aim of these trips was to catch as many unique animals as possible, it was decided to use a ‘snapshot' technique where traps would be moved to a new site each day to maximise the number of new devils caught and reduce the number of re-captures. In sites of high devil abundance two nights trapping maximised the chances of catching any possible diseased animals. Likewise, in sites of very low devil abundance trapping was extended to two nights to maximise chances of catching any devils in the area. Prior to the beginning of the disease front trips, two 5-day reconnaissance trips were conducted to determine the best areas to locate transects. Map 1 indicates the locations of traps deployed by each team.
A total of 231 individual Tasmanian devils were captured and inspected for presence of devil facial tumour disease. Of these at least thirteen devils have been confirmed as diseased by histology. Three devils were captured by remote cameras clearly showing signs of what appeared to be DFTD - however these cannot be confirmed by histology. The most western extent of DFTD recorded in this survey was approximately 15km west of the last known location of DFTD (Surrey Hills, recorded in 2008). However, the high prevalence of DFTD at Surrey Hills in 2008 suggests that DFTD will have been present further to the west at that time, and the distance travelled from 2008 to 2009 would not have been as great as 15km. The current most westerly point of confirmed disease is just to the east of the Murchison Highway. To date no confirmed cases of DFTD have been recorded west of the Murchison Hwy.
There was an obvious gradient of devil abundance from the north to the south, with 50 devils caught by one team in the north and 11 by another team over the same period of time in the south. The very different habitat and the difficulty of access in the southern regions makes it difficult to catch devils and even harder to locate the disease. Our ‘snapshot' method of trapping for these trips will need to be revised for these areas of lower devil abundance before we re-trap in any of these areas.
suggests that DFTD will have been present further to the west at that time, and the distance travelled from 2008 to 2009 would not have been as great as 15km. The current most westerly point of confirmed disease is just to the east of the Murchison Highway. To date no confirmed cases of DFTD have been recorded west of the Murchison Hwy.
