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Tasmanian devils develop effective resistance to contagious cancer
In the last twenty years, an infectious form of cancer has spread to wild Tasmanian devils. The disease spreads rapidly and more and more animals die of DFTD. Conservationists and veterinarians have been looking for a long time for ways to prevent the extinction of the animals also called bag devil. Researchers now realized that devils are rapidly evolving to build cancer resistance.
A team of scientists found that the so-called Tasmanian Devil is developing resistance to the common, deadly form of cancer. This could save the Tasmanian devil himself from extinction. The physicians published the results of their study in the journal Nature Communications.
Bag devils suffer from a special form of cancer. This can be transmitted from animal to animal. For a long time it looked as if the Tasmanian devil would die out with this cancer. Researchers now found that the animals develop resistance to the deadly disease. (Image: melanieplusdaniel.de/fotolia.com) DFTD is transferable
Cancer usually arises in a host and then dies with it. In vertebrates, there are two known types of cancer that develop differently. The so-called Canine Transmissible Venereal Cancer in Dogs and Devil Facial Tumor Disease (DFTD) in pouches. These types of cancer have evolved in the course of evolution an extraordinary way of transmission. The cancers do not just grow in a single host. You can transfer to other animals. Because these cancer cells are all derived from a mutant cell, this cancer is virtually immortal, the researchers say. Another study has previously found that some animals can transmit cancer. Not only dogs and devils can transmit cancer, also mussels are able to.
Bag Devils develop resistance to DFTD
To grow in the new host, the tumor cells must prevent recognition and rejection by the immune system. The cancers transmitted by the devil and the dog have developed sophisticated mechanisms to escape the host's immune system, the experts explain. However, the results of the new research suggest that pouched devil forms a resistance to its deadly disease.
Bag Devil important to contain invasive species
The Tasmanian devil fulfills an important task. The marsupial, for example, helps to contain the number of destructive wildcats on the island of Tasmania. With the advancing extinction of the bloodsuckers, invasive species have become more and more active, say the scientists.
Populations of the bag devils has been reduced by 80 percent
DFTD was first discovered in the mid-1990s in northeastern Tasmania. Meanwhile, this cancer has spread slowly over the years to the south and west, say the doctors. In a few years, all parts of Tasmania will be affected by the disease. At present, only the northwest coast of Tasmania and parts of the southwest are disease free. Since the spread of DFTD, the bloodsucker populations have decreased by at least 80 percent, the experts explain. In some areas, more than 90 percent of the animals died within six years of a local disease outbreak.
Bag devils have fewer and fewer offspring
Most bagged devils die of DFTD during their sexual maturity. Before the deadly cancer, the devils usually produced three offspring in their lives. Meanwhile, most Tasmanian devils have only once again offspring.
Effects of the extinction of bag swells
The extinction of the bag devil would have a huge impact on the rest of the ecosystem. There could be a loss of other species. For example, wild cats have already increased their activities and, accordingly, the populations of small mammals that prey on cats have already declined.
Significant changes in DNA detected in bag tubers
Andrew Storfer of Washington State University and Paul Hohenlohe of the University of Idaho studied the data of the genes of bag swells. These data were from the time before DFTD occurred and about 8 to 16 years after DFTD spread. We identified significant changes in the DNA samples of devils in two small regions. DFTD is widespread in these regions, scientists say. Five out of seven genes in the two regions were associated with cancer or immune function in other mammals. This suggests that the Tasmanian Devil actually develops resistance to DFTD, say the authors. Evolution is usually a very slow process. However, the changes noted would already occur four to eight generations after the disease first broke out.
What causes the rapid development of the bag devil?
So far, our studies have shown that at lower rates of DFTD pouch devils show certain changes in their immune response. The new genetic results may now provide an explanation, experts say. Rapid development requires already existing genetic variation. Our findings are surprising because Tasmanian devils actually have low genetic diversity, the researchers add.
DFTD is also developing
A development is not to be found only with the devils. The disease continues to develop. DFTD meanwhile no longer tries to kill the host before it has spread to a new host. In addition, the disease tries to overcome their defenses by their development, explain the experts.
DFTD may help us understand how cancer can become transmissible
Our findings suggest that the Tasmanian Devil will escape evolution from DFTD. However, it is important to develop strategies that help the bag devil in their struggle for survival, the doctors say. In addition, DFTD represents a unique opportunity to study the early stages of the development of a new disease and the transmissible cancer of its animal host. Through this research, we can understand how cancer can become transmissible and how the affected hosts respond to it, the authors explain. (As)