Anne-Maree Pearse, Launceston Mount Pleasant Laboratories, Tasmania
Part of the show Your Questions, Infectious Cancer and Louisiana Wetlands
Chris - For the past few years, people have been noticing something horrible happening to an animal called a Tasmanian Devil. This is the world's only carnivorous marsupial, and they have some nasty habits, such as biting each other. They've been developing horrible facial tumours that eventually kill them by preventing the Devils from eating properly. Nobody knew where these tumours were coming from or what was causing them. But now they think they know, and what's really spine chilling about this is that it looks like this is an infectious cancer that one animal can pass to the next.
Anne - Maree- It became very clear about three years ago that the Tasmanian Devil's numbers were in great decline and they were in decline because they were dying of Devil Facial Tumour Disease. It generally starts around their mouths or around their lips and grows from there. Devils have the most disgusting behaviour. They fight over everything and they bite each other around the face. In other words they sort of jaw wrestle. These tumours are occurring where these wounds are more or less. They get very large and eventually the devils die, generally of starvation because they're unable to feed.
Chris - So the fact that you've got an injury on one devil which then turns into a tumour, and it's inflicted by another devil kind of suggests that this must be some kind of infectious phenomenon.
Anne - Maree - Yes. Normally in tumours you will find a common cytogenetical or chromosomal break point which actually defines the disease. I expected to find this in the devil with various random rearrangements around it. When I looked at them they were just totally rearranged. It was a massive amount of rearrangement. I looked at the next animal and it was exactly the same, and there were no sex chromosomes in animals of either sex. When you get something as complicated as the mix up in these chromosomes in this cancer, and when you can't find any sex chromosomes in the cancers in animals of either sex, you start to think that you've got an infectious cell line.
Chris - But this raises the obvious question, if you can transmit tissue from one devil to the other, that's almost analogous to an organ transplant. So why isn't it rejected? Why doesn't the devil's immune system just kick in and get rid of the hostile tissue?
Anne - Maree - Well this is another part of the puzzle. The devils' immune system isn't doing it. We know that either the cell line itself or the infectious cell line is capable of sliding under the devil's immunological radar, or that there's something wrong with the devils' immunity.
Chris - Is this the first time that anyone's spotted a disease like this, or are there other examples?
Anne - Maree - There is an infectious dog tumour, a canine venereal sarcoma, which is believed to be spread that way. There is a difference between it and the devil disease, which is that the dog's immune system can overcome it, and it regresses.
Chris - So to what sort of extent is this affecting devil populations in Tasmania? Is this restricted to a small part of the population or is it having a major impact?
Anne - Maree - We're talking about a major impact. The devils are affected in slightly over 50% of the Tasmanian mass, and it seems to be spreading.
Chris - And is there any chance of curing it?
Anne - Maree - We've had no attempts at curing it because you can't catch every devil in Tasmania and give it chemotherapy. But wouldn't it be lovely if we could find a vaccine?