Salvation for the Tassie devil

Researchers have discovered why the Devil Facial Tumour Disease (DFTD) has been so devastating, allowing it to wipe out 90% of some native Tasmanian devil populations.

Published online in the Proceedings of the National Academy of Sciences, a team of researchers led by Dr Katherine Belov from Sydney University's School of Veterinary Science has confirmed that the tumour is a contagious clonal cell line — essentially a tissue graft that originated from a single source and is now passed between individuals.

"The tumour genotypes are genetically identical (clonal) across the disease range. However, tumour genotypes are different to host genes. We propose that this tumour arose in a single individual and has spread through the population by biting during fights for food and mates," said Belov.

"We found that the devils do not mount an immune response against the tumour. This was due to a loss of genetic diversity in the most important immune gene region of the genome: the Major Histocompatibility Complex (MHC). Matching of MHC genes is the key to successful tissue or organ transplants. In the case of the devil, genetic diversity at MHC genes is so low, and the MHC type of the tumour and host are so alike, that the host does not see the tumour as "non-self'."

DFTD emerged in the devil population 10 years ago and has steadily spread throughout Eastern Tasmania, decimating devil numbers and threatening the existence of the species in the wild.

"What also worries me is that many other wildlife populations are going through similar bottlenecks — koalas on Kangaroo Island, platypuses on King Island. Loss of genetic diversity in these genes just opens the door for emergence and rapid spread of new and old disease," said Belov.

This information provides a deeper understanding of the nature of the disease and will aid in developing effective disease control strategies.

"Essentially, there are no natural barriers to the spread of the disease, so affected individuals must be removed from populations to stop disease transmission."