一本教會你“做對”題的6級閱讀書 day14 passage6
Passage 6 Decoding the Tasmanian Devil’s Deadly Cancer
面部腫瘤病威脅“惡魔”生存 《時代周刊》
[00:01]For such a foul-tempered, fierce and smelly creature,
[00:06]the Tasmanian devil is beloved in its native Australia,
[00:12]where it is considered a symbol of the country's frontier toughness.
[00:17]But as fierce as it is, the devil is in danger of going extinct.
[00:23]It's not an issue of predators or hunters but of a peculiar,
[00:29]transmissible disease. Devil facial tumor disease (DFTD)
[00:36]causes tumors to form in and around the mouth of infected devils;
[00:42]the tumors eventually grow so large that they prevent the animal
[00:47]from feeding and lead to starvation. First discovered in 1996,
[00:54]the cancer has spread swiftly through the Tasmanian devil population,
[01:00]killing more than 70% of the island's animals.
[01:04]If nothing is done to stop the disease,
[01:09]the devils could go extinct within 35 years.
[01:14]But new research on the origins of the fatal cancer suggest
[01:19]that methods for rapid diagnosis and even a vaccine
[01:24]against the disease may be possible.
[01:28]Researchers have identified genetic markers for the disease,
[01:33]which should allow doctors to distinguish facial tumor disease easily
[01:39]from other cancers that afflict the Tasmanian devil, and could eventually
[01:45]help determine a genetic pathway to attack the tumor itself.
[01:52]DFTD is a virtually unique cancer in
[01:57]that it is spread from animal to animal via biting
[02:02]or other physical contact - one of only three cancers
[02:07]that are thought to spread this way.
[02:10]While some human cancers can be linked to transmissible pathogens
[02:16]such as cervical cancer,
[02:18]which is caused by the human papillomavirus in DFTD,
[02:24]infected devils actually transmit the tumor itself
[02:29]to other devils when they bite.
[02:33]Through genetic analysis, the Science team was able to confirm
[02:38]that the tumors being spread from devil to devil
[02:42]were the same genetically identical, exact clonal copies.
[02:48]Using genetic sequencing technology,
[02:52]the team also uncovered the tumors' transmission,
[02:57]which means the set of genes that are activated in tumors.
[03:02]Those activated genes best matched those of Schwann cells,
[03:09]which gave the team a clue as to where the disease originated
[03:14]that's important because devils
[03:17]are unusually amenable to a number of different cancers,
[03:22]and a quick diagnosis
[03:24]before the facial tumors get out of control would be helpful.
[03:30]Better diagnoses may lead to more targeted prevention efforts.
[03:36]Right now the only way to slow the spread of the disease
[03:41]is simply to separate healthy devils from infected ones.
[03:47]Naturalists are creating "devil's islands," cancer-free areas
[03:52]in Tasmania where healthy devils can live and breed.
[03:58]But that alone may not be enough to save the animal.
[04:03]The devils will eventually need a vaccine,
[04:06]and there is hope that this research may help scientists develop one.
[04:12]The team collectioned a catalog of devil genes that affect the tumor
[04:17]and may contribute to its growth;
[04:21]these could be useful targets for designing a future vaccine.
[04:26]The difficulty will be creating a treatment that attacks the tumor,
[04:33]but spares healthy cells. Tough as they are,
[04:37]Tasmanian devils still need a lot of help.
