Tasmanian devil pulls the way home from extinction | Science

Along Elizabeth PenisiDecember 10, 2020, 2:00 pm

For decades, horrifying facial cancer has devastated the Tasmanian devil. When chunky raccoon-sized marsupials meshed with each other, they spread from animal to animal, and infectious cancer killed up to 80% of the Tasmanian demons, their only hometown for thousands of years. Some researchers believed that extinction was inevitable.Now new research ScienceSuggests that the remaining 15,000 demons have reached the detent with cancer. Until recently, it had spread exponentially like a pandemic coronavirus among humans in many parts of the world. However, geneticists have calculated that each infected demon has begun to transmit tumor cells to one or less other demons. It may mean that the illness may disappear over time.

“This is a promising sign for the future,” says Gregory Woods, an immunologist at the University of Tasmania in Hobart, who was not involved in the study. Along with two other recent studies, the findings show that changes in the behavior of the devil, and perhaps the emergence of less toxic tumor cells, may be limiting the spread of the cancer, for breeding the devil in captivity. It suggests that desperate efforts may not be necessary. “”[This] A deeper understanding of the link between host behavior and infectious diseases may help reveal new insights that can help both the devil and other wildlife facing the threat of emerging infectious diseases. Maybe, “says Vanessa Ezenwa, a disease ecologist at the University of Georgia in Athens.

Infectious cancers are rare in mammals, and the demons named after their nocturnal screams and growls are almost lonely.However, since 1996, researchers have Began to notice More and more demons with tumors. The sick animal infected others with cancer cells during the mating battle, fighting for the cleaned carcasses, and causing the rapid spread of Devil Makeup Disease (DFTD). Tens of thousands of demons have died, and conservationists have established captive breeding programs to create reserve populations for reintroduction.

The dynamics of the disease are complex, according to a recent study led by cancer geneticist Elizabeth Murchison of the University of Cambridge.Her team Genetic analysis of over 600 tumor samples Collected between 2003 and 2018, 5 genomic versions were found. Three of them are widespread, and some demons are infected with multiple types. According to a November 24 study, its complexity can hinder efforts to develop vaccines to overcome cancer. PLOS biology..

To further investigate the spread of rogue tumor cells, Washington State University, Pullman, geneticist Andrew Stofer and his graduate student Austin Patton track the spread of viruses, including SARS-CoV-2. We investigated the temporal differences in the tumor genome, which is a routinely used approach. , Pandemic coronavirus. Since the mammalian tumor genome is much larger than the viral genome, Patton et al. Had to come up with the following method: Analyze their data, Collected from 51 tumors collected from 2003 to 2018.

We focused on 28 genes that appear to be evolving at a constant rate and tracked how specific mutations spread throughout tumor samples over time. It allowed them to infer the rate at which the cancer itself is spreading among the demons. “The application of these methods to infectious cancers is very smart,” says Michael Metzger, a molecular biologist at the Pacific Northwest Institute.

At the peak of the disease in the early 2000s, each infected demon spread the disease to at least 3.5 people, the team reports today. Science.. However, infection has recently slowed and some infected animals do not inherit DFTD at all. Patton suggests that a decrease in demon density explains much of the decrease, as animals come into contact with fewer of their companions. The rest of the demons may also have better immune system and behavioral changes, Patton, now a postdoc at UC Berkeley, speculates.

Survey conducted on December 9th Bulletin of the Royal Society B Support ideas Animal behavior can delay transmission. Rodrigohamede, a disease ecologist at the University of Tasmania in Sandy Bay, and David Hamilton, a behavioral ecologist, conducted contact tracking of the devil. Pursuit showed that once infected, even the predominant and aggressive demons withdrew from others when they became ill. Hamilton, Hamede, and their colleagues report that these individuals were “superspreaders” only early in the mating season. “The fact that they behave this way can have a significant impact on the dynamics of the disease,” says Hamilton.

The· Science The authors of the study oppose plans to introduce captive demons into the rest of the wild population. Increasing demon populations can increase densities and reactivate transmission, and captive animals may lack the resistance accumulated in wild populations. Farr is guessing.

This week’s news is good, but “the devil isn’t out of the woods yet,” warns Max Jackson, an Australian ark conservationist who helps breed captive demons.Indeed, researchers Detects second infectious facial cancer But new discoveries provide hope, says Hamilton. “It seems very unlikely that we will lose them soon.”