As the deadly facial cancer that has drastically reduced the population of Tasmanian devils continues to spread through the species, the main hope for scientists trying to save them from extinction has been to hunt for devils that might be resistant to the disease, and to try to take advantage of that immunity. Reporting in the Proceedings of the Royal Society B, Kathy Belov and her team say they may finally have done just that: Some devils from northwest Tasmania, they say, are genetically distinct from the rest and could be resistant to the disease.
Belov says that most Tasmanian devils have immune systems so closely related that they’re all susceptible to the disease, which spreads when the devils bite each other on the face and leave behind tumor cells. The bitten devils’ immune systems don’t recognize the tumor cells as foreign, allowing them to take hold. Scientists have given the iconic marsupial as little as 25 years left if efforts are not made to solve the cancer riddle. The population has dwindled by a whopping 70 per cent since the first reported case of devil facial tumour disease in 1996 [Sydney Morning Herald]. Previous research showed that the marsupials are more socially linked that researchers initially believed, which is bad news for those trying to contain the disease.
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The mysterious and deadly facial cancer that has sent populations of Tasmanian devils crashing now has a known source, according to findings published last week in the journal Science. The ailment originated in nerve cells of the devils themselves.
A genetic analysis of tumors from Tasmanian devils widely separated geographically shows that all the tumors are virtually identical and distinct from the animals’ own genomes…. The tumors probably arose from Schwann cells, which normally play a role in protecting and cushioning nerves [Los Angeles Times]. Tasmanian devils have a lot of nerves on their faces near their whiskers, the researchers note, and therefore have Schwann cells there. Team member Jenny Graves says the tumor could have arisen in one cell in one animal two decades ago, and then passed from devil to devil as they bit each other. The disease has already killed 60 percent of the population.
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Saving Tasmanian devils from the infectious cancer that has quickly rendered the small marsupials an endangered species will be an even harder than we realized, according to a new study. The latest bad news from Tasmania: Researchers have found that devils are not solitary creatures with small social networks, but instead frequently interact with other devils, allowing for faster spread of the disease. The devastating cancer, known as devil facial tumor disease, is spread by biting, something the aggressive animals apparently do a lot of.
Investigating the social behaviour of devils, which are nocturnal, forest-dwelling and mate underground is tricky [ABC Science], notes lead researcher Rodrigo Hamede. To get around this difficulty, Hamede outfitted 46 wild devils in a disease-free area with radio collars that recorded every time one devil approached within 12 inches of another–close enough to bite. The scientists found that all 27 of the devils from which intact collars were recovered belong to a single large social group. Each animal is connected to all the others, either directly or through connections with other animals. The finding suggests that if any one of the animals becomes infected with the facial tumor disease, the cancer would spread to the entire network [Science News].
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In a small step forward in the scientific effort to save the Tasmanian devil from the infectious disease that threatens the species with extinction, researchers have developed the first blood test for the ailment known as devil facial tumour disease (DFTD). Previously it has not been possible to determine whether a Tasmanian devil had DFTD until symptoms, such as facial lesions, appeared. However by early detection the diseased animals could be separated (and possibly culled) from healthy animals in the wild [Times Online]. The captive populations that are being kept as insurance against possible extinction could also be tested routinely.
Says researcher Robert Shellie: “We think it is quite a significant breakthrough. In a nutshell, what we have done is develop a blood test for DFTD. It’s a simple test and requires … only a drop of blood from an ear-prick. To be able to determine whether the disease is there, before you can see tumours on the faces of the devils, means that we can detect the disease at a much earlier stage” [The Australian].
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Researchers had high hopes for Cedric the Tasmanian devil: They believed he was the first member of the species to be immune to the deadly facial cancer that is rapidly devastating devil populations. Now, in a major setback, Cedric has grown two small tumors and researchers are back to square one. Many experts believe that the infectious cancer, called devil facial tumor disease, could drive the species to extinction within 20 years if it goes unchecked.
Cedric was captured in western Tasmania last year, along with his half-brother, Clinky. Both were injected with dead tumours by scientists. Clinky produced no antibodies, but Cedric did, and appeared to have built-in defences against the illness [BBC News]. However, the next step yielded worse results. Researchers injected two live strains of the disease into Cedric’s cheek in an attempt to prove his immunity, but two small tumors grew at the injection sites. The tumors were surgically removed last week, and while Cedric is expected to make a full recovery, his love life has been put on hold by the researchers. They were trying to get him to mate so he would pass on his genes. Now they’re unsure if Cedric is naturally immune to the disease [ABC News].
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Australia’s Tasmanian devils are breeding at younger ages in response to a strange form of infectious cancer that is spreading rapidly through devil populations. The feisty marsupials are now reproducing before the lethal cancer strikes them down—a response that may be the species’ only chance to avoid extinction.
Researcher Shelly Lachish explains: “In a normal, healthy devil population the females would rarely breed before the age of two, but now 60 per cent of one-year-olds in diseased populations have produced young…. They are teenagers in human terms. It’s a remarkable change given early breeding was once very, very rare” [Sydney Morning Herald]. While some researchers believe this to be an example of rapid evolution, skeptics say the case is not yet closed.
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