A study which claimed Tasmanian devil facial tumour transmission was slowing has been called into question by new research.
Devil facial tumour disease (DFTD) wiped out about 70% of the iconic devils between 1996 and 2021, before reports began to emerge that its spread was slowing.
DFTD is spread through the transfer of living cancer cells between animals. This occurs frequently as the marsupial predators are prone to fight over mates and food. The parasitic cancer quickly leads to large tumours on the face and neck, sometimes spreading to other parts of the body.
It is caused by the transmission of two different types of cancer cell – DFT1 and DFT2.
Animals infected with the tumour struggle to feed and often starve to death. Once the cancer becomes visible, it almost always leads to death.
In 2021, a study showed that 25 years of DFTD’s spread had a massive impact on the Tasmanian devil population. The number of devils on the island of Tasmania shrank from 53,000 in 1996 to only 17,000 in 2021. The same study suggested that DFTD covered more than 90% of the devils’ range in Tasmania. As a result, Australia’s largest remaining marsupial carnivore was listed as endangered.
But just a year earlier, in 2020, research led by Austin Patton – then at the University of California, Berkeley – suggested that rate of DFT1 transmission was slowing.
That study claimed that DFT1 had shifted from an emerging disease to one that was endemic in the devil population. It had, therefore, become a stable and ever-present disease among Tasmanian devils that would not increase in spread.
Today, new research published in the Royal Society Open Science journal questions the conclusions of Patton et al.
“We show that the study is based on erroneous mutation calls and flawed methodology and its conclusions cannot be substantiated,” the authors of the new study write.
According to the study, which was led by University of Cambridge researchers, Patton et al. did not read enough DNA sequences of DFT1 to give an accurate picture of the spread of the cancer. The authors say that, as a result, the 2020 findings presented an average of about 47% false-negatives in the genotyping of DFT1.
The authors write: “At present, however, there is no evidence that DFT1 has shifted from emergence to endemism and the outlook for Tasmanian devils remains uncertain.”
So, DFTD likely continues to be a massive problem for the Tasmanian devil population. Conservation efforts continue in a bid to save the marsupial.
