Is it possible to save the devil? It just may be, thanks to the research of Dr. Greg Woods, associate professor of immunology at Menzies Research Institute in Hobart (the capital of Tasmania).
The Tasmanian devils were first diagnosed in 1996 with devil facial tumor disease (DFTD), an infectious cancer that acts more like an STD than a typical wildlife disease. Since then, the devil population has dropped from 150,000 to 50,000 individuals, according to Dr. Hamish McCallum, senior scientist with the Devil Facial Tumor Disease Program at the University of Tasmania.
DFTD is only one of two known clonally transmissible cancers. Transmission occurs when devils bite each other during mating, or when fighting over a carcass. So far, every devil that grows a tumor dies. The tumor cell’s chromosomes are abnormal, rearranged so that they look like they were cut and glued back together. The strangest part is that all tumor cells, from different individuals, all have the same exact chromosomal arrangement.
The rearrangement in DFTD cells has remained unchanged for over 10 years, making them good candidates for research. DFTD could provide clues into how cancer is triggered in humans.
The disease appears to have originated from a genetic change in a single individual, and now the clone of the same tumor cell is being passed from devil to devil. The newly infected devil’s cancer cells should be recognized as foreign invader cells, but the species is so inbred that they have the same label, as if they were all identical twins.
“The tumor has no foreign cell surface markers,” said Dr. Katherine Belov, a scientist in the Australasian Wildlife Genomics Group at the University of Sidney. “If tumor cells get into a devil, its own immune system should be able to see the cells as foreign. That doesn’t happen because the tumor’s cells look like devils’ own cells.”
The devils have been coping on their own by having sex at an earlier age. After the emergence
of DFTD, Menna Jones, of the University of Tasmania, noticed that breeding by 1 year old females increased dramatically in four of her study sites. Since the disease hits at age two, when the devils are sexually mature, they have now begun breeding younger, to help themselves out.
Previously, captive breeding of 500 disease-free devils was suggested. Now, with the work of Dr. Woods, there may be another option.
Dr. Woods began an experimental inoculation program, in which 2 disease-free devils (half-brothers) were inoculated with irradiated devil tumor cells. They were each vaccinated three times, before live tumor cells were administered to them. One devil, Clinky, succumbed to the disease. The other devil, Cedric, developed an immune response and lived. Dr. Woods has
since found a second devil who developed an immune response. Three more inoculated devils from eastern Tasmania developed DFTD, which supports Dr. Woods’ hypothesis that devils from western Tasmania have higher genetic diversity. Early next year, Dr. Woods will begin to search for naturally resistant devils.
If the disease managed to make the species barrier jump, then the next victim could be the devil’s closest living relative, the already endangered, spotted-tail quoll. Cute little critter, isn’t it?
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