January 24, 2008
Tasmanian Devils Plagued with Mysterious Cancer
Scientists on Long Island are fighting the clock against the extinction of the Tasmanian devil -- a small, sharp-toothed mammal with a bone-chilling shriek -- now dying by the tens of thousands due to a mystifying facial cancer.
Researchers at Cold Spring Harbor Laboratory say the disease, passed animal to animal through bites in which malignant cells are transmitted, raises new questions about cancer itself. Caused neither by viruses nor bacteria, the researchers are trying to decipher the molecular underpinnings of the rare affliction, called DFTD -- devil facial tumor disease.
"Tasmanian devils are the world's largest remaining marsupial carnivores, and they are only found on the island of Tasmania," said molecular geneticist Elizabeth Murchison, a native of the island off the southern coast of Australia. She has received a fellowship from the Tasmanian government to study the disease, which metastasizes rapidly within the animals and now affects most populations across the island.
Murchison compared Tasmania's size to that of West Virginia.
Stumpy and beady-eyed with a face only its mother could love, the animals known simply as "devils" to Tasmanians have gotten a bad rap from Americans more familiar with the creatures through depictions of the cartoon character "Taz," a terror-provoking monster.
"The devils are very special," Murchison said Wednesday, underscoring how quickly the cancer is killing them. "It's such a sad story," she said.
Citing figures from Tasmanian government officials, who will visit Wednesday to learn about the research, Murchison estimated that more than 50 percent of devils are affected. On some parts of the island populations have dwindled by as much as 90 percent.
Murchison, with veterinarian Hannah Bender and a team of the lab's top researchers, are hoping to learn enough about the disease to stop it in its tracks.
"It's a very obvious tumor on the face and mouth of the devils," Bender said Wednesday. "They advance to very large, smelly masses.
"The animals can't eat and tend to die of starvation. It's quite an aggressive cancer that infiltrates many, many organs and spreads like wildfire," Bender said.
On the sprawling Cold Spring Harbor campus where questions involving human cancers have long held sway, the team has riveted its attention on several intriguing features of the devil cancer.
The speed with which the disease spreads initially suggested viral transmission, but further study in this country and Australia hinted at something rarer, and possibly more insidious.
"It is a neuroendocrine tumor," Murchison said, which invades the nervous system and hormone-producing tissues. She noted its similarity to human Merkel cell carcinoma, a rare, aggressive type of cancer that forms just under the skin.
She, Bender and the rest of the team are also comparing genes within the animals' tumors to learn more about the disease, which is characterized by wildly deranged chromosomes.
Some of that research is also being done by Anne-Maree Pearse of Tasmania's Primary Industries Department. She was among the first to observe that unlike most cancers, the tumor cells didn't seem to originate within the tissue of individual animals but were passed, like mystery cancers, in devil-to-devil contact.
Pearse and other Australian scientists had searched for evidence of a virus or another vector but couldn't find one, and as a result, concluded the animals were developing cancers from exposure to an external source. Closer study revealed that the cancerous cells were being transmitted from animal to animal during fighting and biting, passing the disease with extraordinary speed.
Bender noted only a rare canine condition bears any resemblance to this mode of transmission, but the disease dogs develop as a result is not fatal.
Among the factors that endanger a species' survival, the cancer killing the devils "is probably the rarest and least common reason," said Lee Poston of the World Wildlife Fund in Washington, D.C.
Saving the devils is vital, Poston added Wednesday, because "even though it is a cliche, extinction is forever. Once we lose a species we will never see it again."
Back in Tasmania, Murchison noted, saving the devil is seen as vital _ another native, the Tasmanian tiger, has already vanished. Tasmania remains "quite a haven of biodiversity," she said. "Species have survived there that have not survived on the mainland."