• Triple Helix

Cancer as Contagion: The Tasmanian Devil Facial Tumor Disease

Written by Elisa Dong '24

Edited by Megan List '24

Credit: Wikimedia Commons (1)

The world’s largest carnivorous marsupial: the size of a small dog, endemic to the Australian island of Tasmania, and winner of the title “Strongest bites per unit body mass of any predatory land mammal.”


Tasmanian devils face an unusual and devastating epidemic: a transmissible cancer known as devil facial tumor disease (DFTD), with a near 100% fatality rate. Once the cancer spreads to a host devil, it escapes immune recognition, becomes malignant, and develops a disfiguring mass on the face that interferes with the devil’s feeding habits. Death often results within 9-12 months—quick, and lethal [1]. Since the disease first emerged in 1996, devil populations have plummeted by 80%, evoking catastrophic prospects for the survival of the species [2].


The origins of DFTD in tumor cells is markedly unique. As of 2022, only three transmissible cancers have been identified among mammals: dogs, Syrian hamsters, and Tasmanian devils. Six more transmissible cancers are known among bivalves (e.g. mussels and soft shelled clams) [3]. With a scant total of nine transmissible cancers detected among the millions of studied species on our planet, the transition from genetic disease to contagious organism constitutes an incredibly rare event.


How does a tumor become transmissible in the first place? Malignant cancer, a genetic disease of uncontrolled cellular replication, is characterized by the spread of mutated cells through nearby cells, tissues, and body parts. These transmissible tumors succeed in colonizing a new host by escaping their immune system and adopting their resources, just like any other infectious disease. All cases of DFTD originate from a single, mutated cancer cell, evidence that the disease does not induce cancer, but rather is the cancer itself, as opposed to diseases like HPV [3]. Contrary to the traditional paradigm of cancer as a genetic disease, this contagious cancer spreads from host to host and uses the mutations that occurred in the cells of the original devil to disrupt the functions of a new, unsuspecting host.


Tasmanian devils are particularly vulnerable to this development due to their low genetic diversity and population size, established by an evolutionary bottleneck that occurred in their migration from the Australian mainland [3, 4]. This can vastly increase the risk of deleterious mutations accumulating within the population and leave them with a lower capability to adapt and evolve.


By the 1990s, researchers began to notice Tasmanian devils succumbing to a facial tumor that spread through their mating activities of biting and fighting. Notably, this left the devils who were most reproductively fit—the ones engaging most aggressively in mating behaviors—with an increased susceptibility [5]. In 2003, the Tasmanian government put out $1.8 million in funding to increase conservation efforts, but the population continued to decline, up to 50% in just 2007 [6].


These facial tumors had profound ecological effects on the species. Devils, known to go through multiple rounds of mating, would now only reproduce once due to drastically shortened lifespans, and reproduction would begin earlier due to reduced competition [7]. The population’s very life history was altered in just a couple of generations.

Credit: Getty Images

Biting remains a part of the Tasmanian devil’s mating ritual, largely responsible for the spread of the facial tumor.


For a disease that quickly threatened to push Tasmanian devils to the brink of extinction, researchers and conservationists rushed to find solutions. Populations were translocated to islands or isolated behind barriers, and monitored for signs of disease. Vaccines were also put into trial—evidence from a 2021 experiment showed that a prophylactic vaccine could potentially prime the immune system before infection, but complete tumor regression in Tasmanian devils remains elusive [8].


Thankfully, in 2022, long-term field studies and simulation modeling suggest that devil-DFTD coexistence is a more likely scenario than extinction. Research from one study published in 2020 used phylodynamics to quantify the precipitous decline of DFTD’s recent transmission, suggesting that it had transformed from emergent to endemic within the devil population [9]. Once unfathomable, the disease’s assault on the devils is showing signs of waning.


The struggle against DFTD is far from over, requiring a combined, interdisciplinary effort of detection, breeding programs, vaccine development, and more. But while devils are not quite in the clear—yet—recent developments, aided by human involvement and conservation efforts, makes a future of saving these critters a genuine possibility.

Credit: Aussie Ark


End note: The author chooses not to include photos of the Tasmanian devil facial tumor due to the graphic nature of their injuries. Please note this warning if you choose to search for them!

 

References

1. Hamede R, Lachish S, Belov K, Woods G, Kreiss A, Pearse A-M, Lazenby B, Jones M, McCallum H.. 2012. Reduced effect of Tasmanian devil facial tumor disease at the disease front. Conserv Biol 26:124–34.


2. Lazenby BT, Tobler MW, Brown WE, Hawkins CE, Hocking GJ, Hume F, Huxtable S, Iles P, Jones ME, Lawrence C, et al. 2018. Density trends and demographic signals uncover the long‐term impact of transmissible cancer in Tasmanian devils. J Appl Ecol 55:1368–79.


3. Ostrander EA, Davis BW, Ostrander GK. Transmissible Tumors: Breaking the Cancer Paradigm. Trends Genet. 2016 Jan;32(1):1-15. doi: 10.1016/j.tig.2015.10.001. Epub 2015 Dec 11. PMID: 26686413; PMCID: PMC4698198.


4. Bruniche-Olsen A, Jones ME, Burridge CP, Murchison EP, Holland BR, Austin JJ.. 2018. Ancient DNA tracks the mainland extinction and island survival of the Tasmanian devil. J Biogeogr 45:963–76.


5. Wells K, Hamede RK, Kerlin DH, Storfer A, Hohenlohe PA, Jones ME, McCallum HI. Infection of the fittest: devil facial tumour disease has greatest effect on individuals with highest reproductive output. Ecol Lett. 2017 Jun;20(6):770-778. doi: 10.1111/ele.12776. Epub 2017 May 10. PMID: 28489304; PMCID: PMC6759051.


6. Bostanci, Adam. "A devil of a disease: Tasmanian devils are being wiped out by a deadly facial cancer that may spread when the animals fight each other." Science, vol. 307, no. 5712, 18 Feb. 2005, p. 1035. Gale Academic OneFile, link.gale.com/apps/doc/A129807753/AONE?u=anon~6bdb2d21&sid=googleScholar&xid=a661c80. Accessed 13 Nov. 2022.


7. Jones ME, Cockburn A, Hamede R, Hawkins C, Hesterman H, Lachish S, Mann D, McCallum H, Pemberton D. Life-history change in disease-ravaged Tasmanian devil populations. Proc Natl Acad Sci U S A. 2008 Jul 22;105(29):10023-7. doi: 10.1073/pnas.0711236105. Epub 2008 Jul 14. PMID: 18626026; PMCID: PMC2481324.


8. Ruth Pye, Jocelyn Darby, Andrew S. Flies, Samantha Fox, Scott Carver, Jodie Elmer, Kate Swift, Carolyn Hogg, David Pemberton, Gregory Woods, A. Bruce Lyons "Post-release immune responses of Tasmanian devils vaccinated with an experimental devil facial tumour disease vaccine," Wildlife Research, 48(8), 701-712, (9 December 2021)


9. Patton AH, Lawrence MF, Margres MJ, Kozakiewicz CP, Hamede R, Ruiz-Aravena M, Hamilton DG, Comte S, Ricci LE, Taylor RL, Stadler T, Leaché A, McCallum H, Jones ME, Hohenlohe PA, Storfer A. “A transmissible cancer shifts from emergence to endemism in Tasmanian devils,” Science, Vol. 370 No. 6522, (11 Dec 2020)


IMAGE CREDITS

(1) Wikimedia Commons

(2) Getty Images

(3) https://www.aussieark.org.au/devil-ark/


1 view0 comments

Recent Posts

See All

Written by Yaffa Segal '26 Edited by Lisa Liong '25 Have you ever wanted to visit the Amazon Rainforest? Or go on safari? Imagine visiting the rich landscapes our natural world has to offer. Feel the