*Pic: ABC pic of President Xi Jinping’s wife Madame Peng Liyuan cuddling a Tassie Devil baby ... from ABC picture gallery, HERE
What’s killing Tassie devils if it isn’t a contagious cancer?
Scientists have been trying to figure out the cause of the deadly cancer affecting so many Tasmanian devils but the research doesn’t seem to be providing many useful answers. What if they’re looking in the wrong place for a cause and a cure?
The Tasmanian devil is Australia’s largest carnivorous marsupial. It is currently listed as “endangered” and risks becoming extinct. Most of the devils in Tasmania are developing ugly tumours on their faces due to what is called devil facial tumour disease (DFTD), and it is nearly always fatal.
The disease was first observed in 1996 and research into it began in 2003.
In 2006, two Tasmanian government researchers, Anne-Marie Pearse and Kate Swift, published a short article in the scientific journal Nature suggesting that the devil disease was a contagious cancer spread from one devil to another by biting. This hypothesis became the basis for much subsequent research.
It was a bold and unorthodox theory, especially considering that there are only a handful of contagious wildlife cancers around the world. Furthermore, the pathway of spread by biting would be unique worldwide.
Theory doesn’t bite
It is true that Tasmanian devils bite each other in ritual fights, but their teeth are not sharp and not an obvious mechanism for spreading cancer. Furthermore, various complications soon emerged from the biological research.
To spread from one devil to another, the genetics of the devils have to be similar so rejection of the foreign cells does not occur. It was proposed that devils had limited genetic variability, but later this turned out to be incorrect. There are not even any studies that conclusively show that the devil cancer is transmissible from one animal to another.
Eventually the research seemed to reach a dead end, with too many contradictions. Meanwhile, devils kept dying.
There is another possible explanation for the devil disease, either its origin or its spread or both: environmental chemicals.
Look to the trees
In Tasmania, huge areas are taken up by plantation forests, and these are regularly sprayed with pesticides and poisons.
Of special concern is the pesticide atrazine, used to control grass and broadleaf weeds. The Australian Pesticides and Veterinary Medicines Authority carried out an extensive review and considers atrazine safe to use under current guidelines which include “conditions outlined on product labels”. The Tasmanian government’s information on atrazine says it “does not cause mutations” and is “not likely to cause cancer”.
But there are those who point to research that suggests atrazine is a cancer promoter. The US Environmental Protection Agency had this to say following its review of studies by a federal Scientific Advisory Panel:
Even though the panel agreed with EPA that the epidemiologic evidence does not strongly suggest a link between atrazine and cancer, the panel did not agree that a lack of strong evidence justifies a conclusion that atrazine is not likely to be a human carcinogen.
Also of concern is the poison 1080, used to kill native species that are a key part of the devil diet. The Tasmanian government says devils have a relatively high tolerance to the poison but it also concedes there is a risk of secondary poisoning with three poisoned pademelons likely to be fatal to a 5kg devil.
Plantation forestry pesticides contaminate 44 of 48 river catchments in Tasmania.
So a role for pesticides and poisons seems plausible, because the devil disease is found only in parts of Tasmania where there are extensive forest plantations. Furthermore, because devils, as carnivores, are at the top of the food chain, toxic chemicals in the environment are concentrated in their diet.
Jody Warren is Honorary Postdoctoral Research Associate at University of Wollongong
Brian Martin is Professor of Social Sciences at University of Wollongong
• Kev Rothery, in Comments: The geographic correlation between DFTD and plantation forestry couldn’t be more obvious really, could it? I know I’m not alone in having suspected a causal link for years. I’m not holding my breath waiting for an impartial investigation of course. There’s too much interest vested in the forestry debacle within this state, and our government is therefore blindfolded to the risks to public health and the demise of an iconic island species.
• Dr David Obendorf, in Comments: If nothing else Tasmania lost an opportunity to become research hub for important cancer research when the scientists in UTAS were cowered by the control from DPIPWE and the State Labor Government; the University that lost its independence.
• Dr Alison Bleaney, in Comments: 10 years of a new aggressive cancer in a marsupial that has relatively little known about it (immune system, cell signalling, endocrine and reproductive sensitivities, chemical sensitivities) which lives in an environment of increasing chemical mixtures. The toxic ‘soup’ of pesticides, dioxins, PCBs etc etc present in the water catchments with DPIPWE not knowing what is being used where in what quantity and the legacy of the ‘soup’ remaining in our soils, water and waterway sediments and constantly being added to. There has been no research done on chemicals and DPIPWE reluctantly introduced a raw water sampling programme for pesticides only in 2005; now cancelled after some pretty damming evidence of consistent pollution with highly hazardous pesticides. And still no research on Tas Devils related to chemicals/ toxins in their environment; chemicals they are regularly exposed to as are the ecosystems and Tasmania’s raw drinking water… So the questions have to be asked..Has the toxic soup or some of those chemicals really compromised the ability of the Devil to stay healthy? Are we all at risk? How would we know? As there is very little data on the ‘soup’ and its effects and absence of evidence is not evidence of absence.
• Peter McGlone: Warning to Chinese investors: investing in Van Diemen’s Land dairy company may result in destruction of Tasmanian devil habitat As the Chinese President Xi Jinping is visiting Tasmania, the Tasmanian Conservation Trust is using the opportunity to advise potential Chinese investors that by investing in the Van Diemen’s Land company dairy expansion they may be financing the destruction of endangered species habitats and threatened forest communities.
• Premier Will Hodgman: Welcome President Xi and Madame Peng The President will be introduced to three baby Tasmanian devils.
• ABC HERE: While the Tahune Air Walk and Cataract Gorge did not made it onto the president’s five-hour itinerary, he will get to meet three Tasmanian devil joeys.
• What Christine Milne says about the President Xi visit: Xi_Tas_visit.MP3
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