Facts

1. What caused the Devil Facial Tumour Disease (DFTD)?
2. Can the disease jump species?
3. How long has it been affecting the Tassie Devils?
4. How many Devils are left?
5. How long do the Devils have to live when they become infected?
6. How are Devils dying?
7. How is the disease transferred?

What caused the Devil Facial Tumour Disease (DFTD)? The DFTD was probably caused by a chance mutation. Researchers have looked for evidence that some form of environmental toxin might be involved, but have failed to find any evidence. The disease is able to spread between individuals because Tasmanian devils (particularly in the eastern part of the State) are so genetically similar to each other that they don't recognize the tumour cells as being "non-self" or foreign.

© Tasmanian Department of Primary Industries and Water

We know that all the tumour cells are so genetically similar that they must have been derived from a single individual. Given that the disease has been present since 1996 at least, that individual will now be long dead so we will never know what might have caused the initial mutation to malignancy in that animal.

Can the disease jump species?

There is certainly no evidence at the moment that the disease affects any other species. Given the nature of the disease, which is that the cells themselves are the infectious agent and that they spread because the devils do not recognize them as being "nonself", researchers would not expect it to affect any other species.

The one word of caution here is that the only similar cancer known, which is canine transmissible venereal tumour, has evolved the capacity to affect jackals as well as dogs.

How long has it been affecting the Tassie Devils?

The first case was observed in 1996. The symptoms are so gross and obvious that it cannot have been present much before this time. There is no evidence of the tumour in any museum specimens from before 1996.

How many Devils are left?

This is not an easy question to answer. What researchers do know from spotlighting surveys is that the total population is reduced by more than 50% from its previous levels and there have been reductions of more than 90% in the Northeast. However, spotlighting surveys give a relative estimate of population density, not an absolute population size. In undiseased areas, population densities of devils are in the region of 1-2 per square kilometre. Tasmania's total area is around about 65 to 70,000 square kilometres. So, the population size before disease might have been about 100,000.

Currently, there are almost certainly fewer than 50,000 animals left; it is suspected however, that this is probably closer to 25,000. Of these, perhaps 10 to 15,000 might be in currently uninfected western part of the State. However, all of these estimates are really educated guesswork.

How long do the Devils have to live when they become infected?

Research indicates three to six months from the first appearance of clinical signs. Is not known however, is how long it takes between a devil getting infected and first showing clinical signs. This may be as little as a couple of months or as long as six to eight months. Finding out this latent or incubation period is a major research challenge.

How are Devils dying?

The Devils are predominantly dying from starvation. The cancers are initially mostly around the face and eventually erode away the jaw.

How is the disease transferred?

The DFTD is transferred when Devils bite each other, eat the same meat and mate aggressively. Tumour cells are most likely transferred during biting, which occurs frequently during mating interactions but also during fights over food. Whether it is always an infected "biter" transferring cells to a susceptible "bitee" or whether a susceptible biter can pick up cells from an infected "bitee" is currently unknown. It's also possible that devils may pick up infection by scavenging on another devil that has died from a tumour.