Tasmanian Devil Tumor Disease
Spreading - Nearly 50% Dead
From Patricia Doyle, PhD
Tasmanian Devil Tumor Disease Spreading -
Nearly 50% Dead
ABC Online - Australia
A facial tumour disease is continuing to ravage Tasmania's wild devils, with almost half of the devil population believed lost to the disease. Fears the disease is spreading have been realised, with 3 new cases discovered in the south of the state.
The Devil Task force has released a report detailing progress made over the past 12 months [see part 2 below]. Project manager Alistair Scott says they have established a strong base of information about the disease, but they are yet to discover how or why it is killing so many Tasmanian devils.
The disease has now spread across 65 per cent of the state, with 3 new cases discovered in southern Tasmania. "The disease is across the eastern part of the state and extends as far west as the Cradle Valley, and also down into the south of the state," he said. "To date we haven't recorded the disease on the west coast or in the far north-west, so it's in the eastern parts of the state that the disease is having the greatest impact."
Mr Scott says they do not know how long it will take to find a cause and a cure. "We are dealing with a new disease here that hasn't been recorded anywhere else in the world," he said. Mr Scott estimates that almost one half of the devil population has been lost to the disease.
There is now concern that the disease may be discovered in areas previously thought to be disease-free, like the western and far north-western areas of the state.
Wildlife biologist Nick Mooney says the reduction in devil populations is taking a severe toll on the ecosystem. "Bush hygiene has suffered. Probably there will be an effect in the landscape of other species, and the one I worry about very, very much is that it will give foxes an unprecedented opportunity to be established," he said. "Where you remove devils from the landscape and there is still all the food there, nature won't tolerate that for long, something will happen to react to that."
Department Of Primary Industries,
Water & Environment, Tasmania
Research into the Tasmanian Devil Facial Tumour Disease (DFTD)
Progress Report: January 2005. Executive Summary.
1. Mapping and Monitoring
The impact and distribution of Tasmanian devil facial tumour disease (DFTD) is being monitored in wild populations around the State. DFTD has now been recorded across the eastern half of Tasmania and as far west as Cradle Valley. In recent weeks, the disease has been confirmed at Fentonbury and Adamsfield in the south, and immediately north of Eaglehawk Neck on the Forestier Peninsula. So far, the disease has only been recorded in wild Tasmanian devils.
To December 2004, DFTD had been recorded over 65 per cent of the State and is almost certainly present in a larger area. Mapping and monitoring of DFTD has been undertaken in 3 stages:
1) a snapshot survey in mid-2003;
2) collection of more specimens for analysis and replicating monitoring of a DFTD-affected population, from late 2003; and
3) Statewide monitoring, from early 2004.
1/3 to 1/2 the wild devil numbers in the State 10 years ago are likely to have been lost. The short and medium term effects of DFTD are severe; the long-term effects are not known at this stage.
Assessment for DFTD is hampered by the lack of a pre-clinical test, meaning only devils with visible symptoms can be used for confirmation. Therefore, a very high proportion of a local population, and preferably a large absolute sample, must be physically examined to have confidence in a DFTD-free status; a laborious task.
There is much to be learnt about the effects of DFTD on wild populations and its transmissibility. It will be vital to maintain intensive long-term monitoring at replicated sites.
2. Diagnostic Research and Investigations
Due to the complexity of the research into DFTD, a number of key areas have been identified for investigation. The individual study areas have been grouped in their modalities eg. pathology, cytogenetics, immunology etc. Key collaborations with local and interstate institutions have greatly assisted the diagnostic research effort.
The initial focus for the diagnostic group has been to develop a case definition for DFTD.
3. Relevant Physiological Parameters
This work encompasses haematology, blood biochemistry, immunology and endocrinology. Whole blood and sera samples have been taken from devils in a range of areas across the State. These data are now being analysed.
A number of investigations have been undertaken in an effort to identify possible applications for established diagnostic tests. This work is continuing.
Key outcomes include the development of an effective field sampling unit, documented anaesthesia monitoring, establishment of a sample bank for devil tissue and the development of a number of blood and biochemical reference values for devils.
4. Case Definition of DFTD
This has included histopathological, cytogenetic and transmission electron microscope analysis.
No definitive conclusion can be drawn at this stage from the results of the histology. However the use of immunohistochemistry has shown that the most consistent tumour type isolated appears to be of a neuroendocrine origin. This is the case for animals from a range of geographical areas within the State.
Cytogenetics work has established the Normal Tasmanian Devil karyotype and the chromosome rearrangements of the tumour. This has led to the hypothesis that DFTD may be directly passed from animal to animal by implantation of the cell line during fighting and biting. Further testing of this hypothesis is planned.
5. Identification of Aetiology (Cause)
This may be the hardest question for the diagnostic research program to answer. The process of aetiological identification has been progressed by histopathological, immunohistochemical and cytogenetic examination of the tumour.
The results of transmission electron microscopy of tumour tissue for the presence of virus particles has so far been egative, but work will continue to categorically rule out viral involvement.
A tissue culture laboratory was established in July 2004 and cultures made of tumour cells.
Additional techniques will be employed in the next stage of aetiological investigation. A pilot trial to test samples for the presence of a range of toxins is proposed and may lead to a much larger project.
An epidemic of progressive and apparently transmissible neoplasia has been recorded in Tasmanian devils (_Sarcophilus harrissi_) in the wild since 1997. A detailed description and discussion can be found in posting 20030812.1999.
The disease, later termed "Tasmanian Devil Facial Tumour Disease (DFTD)" is being investigated by a professional team, the last progress report of which is presented.
A video (1 minute 29 seconds) of the field monitoring of DFTD can be seen at the said web-site (go to "animal diseases").
It would be interesting to compare the Tasmanian observations and pathologic findings with the neoplasms described 20 years earlier in 18 Tasmanian devils that were necropsied at the San Diego Zoo; see Griner LA., (1979). Neoplasms in Tasmanian devils (_Sarcophilus harrisii_). JNCI 62(3):589-95. - Mod.AS
Patricia A. Doyle, PhD
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