What Is Devil Facial Tumor Disease (DFTD)?
In the early 1990s, the Tasmanian devil was plentiful throughout Australia's island state of Tasmania. In fact, its numbers were probably at an all-time high. But in the mid-1990s, a strange new disease began appearing in devils in northeastern Tasmania. Affected animals developed large, disfiguring tumors, primarily on the face and neck and inside the mouth, and the disease was invariably fatal. Many diseased animals died of starvation, as the tumors grew so large that they prevented animals from eating. The new disease was given the descriptive name Devil Facial Tumor Disease (DFTD, or "devil disease," for short).
DFTD spread quickly and caused rapid population declines. Its spread followed patterns typical of an epizootic (the animal equivalent of an epidemic), but for several years the cause of infection was not known. Eventually, researchers determined that the disease was an extremely rare example of a directly contagious cancer; that is, the cancer cells themselves (not a microorganism such as a virus or bacterium) are the infectious agent, spreading directly from animal to animal. Transmission occurs when devils bite each other, a frequent occurrence during the breeding season or when animals fight over a carcass. Cells dislodged from an infected animal's tumor enter an open wound on a healthy animal and begin to reproduce; the healthy animal's immune system fails to recognize and destroy the cells, allowing the infection to take hold.
Today DFTD is present through most of Tasmania and has caused an overall population decline estimated at 80%, with local declines measuring above 90% in many infected areas. Some ecologists have projected that the species could become extinct in the wild within the next twenty years, although there is cause for hope. Recent research suggests a small proportion of devils may carry some resistance to the disease. And vaccine trials are under way, with potentially promising results.
The Carnivore Conservancy's field research sites are in northwestern Tasmania, the last part of the state to remain free of DFTD. When we began our research in 2012, all our study sites were disease-free, but we have since begun to see cases at some sites. This has given our research an increased sense of urgency — particularly our behavioral research, as we strive to document as much natural devil behavior as possible in healthy populations while they still exist.
Photo © A. Chisholm 2012.