Since 1996, a transmissible cancer has been wiping out Tasmanian devils in alarming numbers. But now, a new study from Washington State University offers hope that the infectious disease will not push the animals to extinction, as was predicted about ten years ago.
While most cancers remain confined in the body, the cells of devil facial tumor 1 (DFT1) can be transferred to new hosts through biting. These tumor cells are able to resist the Tasmanian devil’s immune defenses and establish a new tumor that is usually fatal.
A research team led by WSU biologist Andrew Storfer has used genomic tools of phylodynamics, which are typically used to track viruses such as SARS-CoV-2, to trace DFT1.
The results of the groundbreaking analysis suggest that the spread of the Tasmanian devil facial tumor disease is slowing down to the point that each infected animal is infecting only one additional individual or less.
“It is cautiously optimistic good news,” said Storfer. “I think we’re going to see continued survival of devils at lower numbers and densities than original population sizes, but extinction seems really unlikely even though it was predicted a decade ago.”
The disease is still very deadly to Tasmanian devils who contract it, which usually occurs through biting and scratching during fights with infected animals. The cancer has reduced populations by as much as 80 percent since it was first discovered.
However, DFT1 appears to be reaching an equilibrium, according to the current analysis as well as evidence from previous field studies. The researchers say that, armed with this new evidence, managers should re-consider the practice of releasing captive-bred devils into the wild.
“Active management may not be necessary and could actually be harmful,” said Storfer. “It looks like the devil populations are naturally evolving to tolerate and possibly even resist the cancer. By introducing a whole bunch of genetically naïve individuals, they could breed with the wild individuals, basically mix up the gene pool and make it less well-adapted.”
The captive-bred individuals who have developed no resistance to DFT1 could also increase transmission of the disease among different groups of devils.
The study is published in the journal Science.
By Chrissy Sexton, Earth.com Staff Writer