Almost 20 years ago, the first case of devil facial tumor disease - a form of contagious cancer among Tasmanian devils - was discovered, a cancer that is threatening to push the animals to the point of extinction. Now, a team of researchers has uncovered a second transmissible cancer in Tasmanian devils, suggesting such a disease is more common than previously believed.
First author Dr. Ruth Pye, from the Menzies Institute for Medical Research at the University of Tasmania, Australia, and colleagues publish their findings in the Proceedings of the National Academy of Sciences.
The Tasmanian devil is the largest carnivorous marsupial in the world, weighing up to 12 kg (26.5 lbs) and growing up to 30 inches in length. While the mammals could once be found roaming around various regions of Australia, they are now only found on the island state of Tasmania.
In May 2009, the Australian Government declared the Tasmanian devil to be an endangered species - a tragedy that has resulted from devil facial tumor disease (DFTD). Since the discovery of this disease in 1996, the Tasmanian devil population has declined more than 90% in some areas.
DFTD is characterized by cancerous tumors that grow around the face, mouth and neck. The cancer is spread between Tasmanian devils through biting, and once infection takes place, the disease spreads rapidly throughout the body, causing death within months.
DFTD is one of four contagious cancers that have been discovered to date; the other three forms have been identified in dogs, soft-shell clams and Syrian hamsters. According to the researchers, transmissible cancers arise when cancer cells develop the ability to spread beyond the host's body to the body of a new host.
Now, Dr. Pye and colleagues have uncovered another form of contagious cancer in Tasmanian devils that they say is genetically distinct from DFTD.
Transmissible cancers 'may not be as rare as previously thought'
In their report, Dr. Pye and colleagues detail the discovery of a Tasmanian devil with facial tumors in southeast Tasmania last year.
The researchers note that the facial tumors of this devil were visually similar to those seen in devils with DFTD. However, on testing the tumors, they found that this devil's cancer possessed different chromosomal rearrangements, making it genetically distinguishable from DFTD.
This new cancer has been identified in eight more Tasmanian devils to date.
These findings, the team says, suggest that contagious cancers may be more common than previously believed. Senior study author Dr. Elizabeth Murchison, of the UK's University of Cambridge, says:
"Until now, we've always thought that transmissible cancers arise extremely rarely in nature, but this new discovery makes us question this belief.
[...] Now that we have discovered that this has happened a second time, it makes us wonder if Tasmanian devils might be particularly vulnerable to developing this type of disease, or that transmissible cancers may not be as rare in nature as we previously thought."
Joint senior author Prof. Gregory Woods, of the Menzies Institute for Medical Research, adds that it is possible there are more transmissible cancers in Tasmanian devils that have yet to be discovered.
"The potential for new transmissible cancers to emerge in this species has important implications for Tasmanian devil conservation programs," says Prof. Woods.
Last year, Medical News Today reported on a study by Dr. Murchison and colleagues that revealed how an 11,000-year-old transmissible genital cancer in dogs is aiding the understanding of cancer evolution.