Community Acquired Cancer a Threat to Endangered Species

    Cancer is difficult enough to treat without being contagious, but Tasmanian devil populations are being faced with just that danger. A paper released by Proceedings of the National Academy of Sciences (“A second transmissible cancer in Tasmanian devils”)—coauthored by Ruth Pye, Ph.D., and senior professor Gregory Woods from the Menzies Institute for Medical Research—suggests that communicable cancer may be more prevalent than previously thought.

    The trend was first noticed by a wildlife photographer in 1996 when a number of individuals began showing signs of irregular skin growths. Researchers investigating the growths later announced that the tumors were not just lesions, but a rare form of cancer that acts like a parasite infecting a host, transmissible in the case of Tasmanian devils through biting.

    While they are widely thought of as “the garbage bins of the bush” for their scavenging behavior, Tasmanian devils got their name for good reason: They are a very competitive species with incredibly strong jaws, and females in particular become highly territorial and combative around their dens. That means one female infected with the parasitic cancer cells is very likely to come in contact with and infect a number of other females, especially during mating seasons when protected areas to birth and feed young are often won by aggression. Biting is also common during hunting and mating encounters.

    Once the disease is contracted, an individual has only months to live. For an endangered species already burdened with the threat of extinction, such a quick and sure killer amid the population has significant long-term conservation implications.

    A specialist in comparative oncology and genetics at the University of Cambridge’s department of veterinary medicine, Elizabeth Murchison, Ph.D., became aware of the issue in 2006 and has been working to understand the disease ever since. She led a group in sequencing healthy and infected Tasmanian devil genomes hoping to separate out the genes responsible for tumor growth.

    Dr. Murchison’s team discovered that the cancer, which in theory should be the same in each infected individual, has actually diverged and mutated while moving across populations. Currently there is at least a second genetically distinct but outwardly indistinguishable cancer being transmitted through the population, which puts into question whether this kind of disease is really that unusual.

    “Previously, we thought that Tasmanian devils were extremely unlucky to have fallen victim to a single runaway cancer that emerged from one individual devil and spread through the devil population by biting,” says Dr. Murchison. “However, 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.”

    The team’s research is invaluable in understanding the disease’s underlying process and developing a vaccine to protect the endangered devils.