But a new study of cancer genomics, published today in the journal Science, has provided a Encouraging fact: the infection rate among wild demons has shown a huge decline since the disease was first recorded, which indicates that the Tasmanian devils would not become extinct due to this cancer.
“This is great news, because it means that the disease would not be spreading through indigenous populations as it used to,” explains study leader Austin Patton, an evolutionary biologist at the University of California, Berkeley. “The contagion is slowing down.”
Decrease in contagion
The disease was first discovered in 1996, although it likely originated in the 1970s or 1980s. In 2015, researchers concluded that Tasmanian devil facial tumor disease is actually a combination of two conditions different, known as DFT1 and DFT2. Although both diseases cause nearly the same tumors and lead to death by starvation, genetically, the cancers are different. And what’s more, they have a different origin: DFT2 arose in a male Tasmanian devil on the far side of the island where DFT1 first originated, in a female.
“Discovering DFT2 was a great surprise for our research group, since transmissible tumors in vertebrates are very rare,” says Bruce Lyons, an immunologist at the University of Tasmania and co-author of the study, published in Proceedings of the National Academy of Sciences.
Very few infectious cancers have been recorded in nature, including those that affect domestic dogs and those that suffer from a type of clam.
To learn how DFT1 spreads in the Tasmanian devil population, Patton and his colleagues used a technique known as phyllodynamics, which is often used to study viruses.
Using genetic analysis, phylodynamic approaches reconstruct how a pathogen spreads and evolves over time. To carry out the analysis, Patton’s team used samples from 51 Tasmanian devil tumors that they began collecting two decades ago.
Around 2003, when the sampling began, the team found the cancer’s spread rate to be 3.5, Patton explains. This means that for every Tasmanian devil infected, there were 3.5 potentially affected animals.
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