Poor Devils
October 29, 2007 9:04 AM   Subscribe

Devil facial tumor disease has ravaged the population of Tasmanian Devils in the last decade. DFTD is a transmissible cancer, i.e. the tumor cells themselves (which differ genetically from their host animal) are the agent responsible. The disease is spread by biting and other contact, and the resulting grotesque tumors interfere with feeding and lead to starvation. Poor immune response may be partially responsible. This is actually not the only such disease: canine transmissible venereal tumor is an analogue that has been known to be contagious since the 19th century. (CTVT, however, gets a proper immune response.)

Wikipedia: DFTD, CTVT.

The evidence for this method of transmission is quite recent. Here are the studies referenced in the articles:
Allograft theory: Transmission of devil facial-tumour disease. (Nature wants your money, though.)
Transmission of a fatal clonal tumor by biting occurs due to depleted MHC diversity in a threatened carnivorous marsupial.
Clonal Origin and Evolution of a Transmissible Cancer.
posted by parudox (7 comments total) 2 users marked this as a favorite
This summer, I saw my first Taz at Featherdale Wildlife Park, about an hour north of Sydney, Australia.

Poor guy was running a figure-eight around the same trees... over and over. I'm sure he didn't have cancer, but it was still a sad sight.
posted by mokolabs at 9:51 AM on October 29, 2007

I'm confused...They say the spread of the disease is in part due to a lack of genetic diversity in the population. Yet their best chance of species survival is to whisk away a few Devils from areas still unaffected. Won't that further limit genetic diversity?
posted by Gungho at 11:32 AM on October 29, 2007

So maybe there are some very good reasons to avoid physical fights with your close relatives other than mere kin selection-- not likely getting cancer, of course, but any transmissible infection well adapted to your genotype (not to mention the whole incest taboo thing).

There is one very intriguing story that makes me think it might be possible for something like this to have arisen even in genetically diverse populations in humans-- say in war with all the associated rape and other sexual irregularity-- the emergence of the incredible HeLa cell line.

This cell line has been extensively used (a little more extensively than researchers knew or would have desired, perhaps) in biomedical research for a long time; it was harvested from a cervical cancer which killed the woman who originated it in !951, and is so vital and vigorous steps have had to be taken in some labs to restrain it:

Because of their avid adaptation to growth in tissue culture plates, HeLa cells are sometimes difficult to control. For example, they have proven to be a persistent laboratory "weed" and they can contaminate other cell cultures in the same laboratory, interfering with biological research. The degree of HeLa cell contamination among other cell types is unknown, because few researchers test the identity or purity of already-established cell lines. It has been demonstrated that a substantial fraction of in vitro cell lines - approximately 10%, maybe 20%, are actually HeLa cells, due to the fact that the original cells in the cell culture have been overwhelmed by a rapidly growing population derived from HeLa contaminant cells. Stanley Gartler in 1967 and Walter Nelson-Rees in 1975 were the first to publish on the contamination of various cell lines by HeLa. [2]

One investigator has suggested it should be recognized as a newly created species.
posted by jamjam at 11:40 AM on October 29, 2007

Gungho, you probably can't really do much about the genetic diversity in the short run (which is all the Devils might have, it seems). But if a healthy population can be physically separated, I can't imagine how the cancer could arise again.
posted by parudox at 11:44 AM on October 29, 2007

See also, jackalopes rabbits with HPV.
posted by Brittanie at 7:41 PM on October 29, 2007

I heard about this a few months ago, when I read an article about the new efforts to find wild devils in mainland Australia, which may yet exist, because they would be so genetically different from those in Tasmania.

It's fascinating that a cancer could spread in this way, and that it could be unrecognized by the immune system. Nonetheless, I wish this weren't in existence for us to be fascinated over, because this is immensely sad. Devils are -awesome- creatures, and to think of their becoming extinct is heartbreaking.

*goes off to snuggle her stuffed devil, Quentin*
posted by po at 4:31 AM on October 30, 2007

Very interesting, Brittanie; the HeLa cell line was apparently also the result of an HPV infection.
posted by jamjam at 6:14 PM on October 30, 2007

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