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A devil and its cancer

Welt am Sonntag (Germany) (German)


Susanne Wedlich

DE | June 01, 2024 · 04:00 AM

The Tasmanian marsupial devil suffers from tumors that are even contagious. Those who were good for nothing came to Australia: criminals and exiles were the first Europeans to populate the continent from 1787. But in Tasmania, the large island in the south of the continent, the new arrivals were kept awake at night by ungodly screeching and sometimes unbearable...

The Tasmanian marsupial devil suffers from tumors that are even contagious. This has already killed off 85 percent of the population. A vaccination from the snack machine is supposed to save it

Those who were good for nothing came to Australia: criminals and exiles were the first Europeans to populate the continent from 1787. And it must have been a very dubious pleasure. Nowhere else are there more poisonous animals, spiders and snakes - and a jellyfish called the sea wasp, the most poisonous animal in the world. In addition, there are sharks and crocodiles - including those that dive in salt water - that were a source of terror. But in Tasmania, the large island in the south of the continent, the new arrivals were kept awake at night by ungodly screeching and sometimes unbearable stench.

The supposed devil turned out to be a marsupial about the size of a dog with dark fur, red ears and a hobbled walking style. As cute as the animal looks with its mouth closed, it quickly becomes clear that you are dealing with a predator as soon as the devil opens it. This is when its huge teeth with truly devilish fangs are revealed. It can open its muscular jaws up to 80 degrees, and the force of its bite exceeds that of a pittbull. Residents of Tasmania say that animals have even penetrated metal to search for food in barns. However, the Tasmanian devil is actually a scavenger. At night, it usually roams the forests alone, devouring everything in its path, including skin, hair, bones and intestines. The animals can eat up to 40 percent of their own weight. Apart from their deafening screeching, they spread a foul odor that is in no way inferior to that of a skunk.

So it's no wonder that the eight to twelve kilogram animal has been given the name devil - and the animals are also extremely beastly when dealing with their own kind. When mating, the males bite into the neck of the females, drag them off and hold them captive for days. A mother then gives birth to up to 40 young, although she only has four teats. With the birth, the devils' fight for survival begins. And it continues. They also fight fiercely for their prey. They are all fought with fierce biting attacks.

It is precisely this ferocity that is now endangering the survival of the entire population. This is because the bloody fights make it possible for a deadly disease to spread among the marsupials(Sarcophilus harrisii): They suffer from a contagious form of cancer that causes large open ulcers to proliferate in the head area of the affected animals. These prevent them from eating. They die because they starve to death or because metastases grow in their bodies. Since the first sick marsupial was discovered in 1996, although the cancer probably developed ten to 20 years earlier, their population has shrunk by 85 percent: animal welfare organizations estimate that around 25,000 of the 150,000 animals that once existed are still alive today. If the trend is not halted, the animals are in danger of becoming extinct in the next few years.

This is exactly what scientists from the University of Tasmania in Horbart, Australia, want to prevent. A team led by wildlife immunologist Andrew Flies has developed a vaccine to save the marsupial devil.

The cancer of the devils is a biological peculiarity. Normally, tumors develop when an endogenous cell escapes the organism's control. The impetus for misguided development is a genetic defect, which can be congenital or acquired through environmental factors such as carcinogenic chemicals or an excess of UV light on the skin. In short, cancer is normally an individual disease that cannot be passed on. Devil Facial Tumor Disease (DFTD) is different: it is contagious. Only three forms of transmissible tumor diseases are known in vertebrates. One affects dogs; the other two are variants of marsupial devil cancer. Originally there was only the DFT1 type, but in 2014 DFT2 was added in southern Tasmania.

All it takes is for males to fight over females or over a carcass. Then they literally fight doggedly with loud screeching. The animals smash their very sharp teeth into each other's faces. If this results in open wounds, the tumor cells - like parasites - can enter the body of healthy marsupials. And multiply.

This is exactly what should not happen. Evolution has equipped the defence system of animals and humans in such a way that it immediately recognizes cells or even just fragments of them, whether healthy or diseased, as foreign and attacks them. This is the reason why people after organ transplants are dependent on medication for the rest of their lives to keep their immune system in check. In the Tasmanian devil, however, this defense reaction against the cancer cells does not occur. This has to do with their peculiar nature, which has lost all the characteristics that could make them recognizable as foreign. The infectious cancer cells are almost invisible from an immunological point of view.

The vaccine that Flies and his colleagues have developed is intended to change this. It should ensure that the immune system recognizes the dangerous cells. The wildlife immunologist was inspired by the coronavirus vaccines from Astra Zeneca and Johnson & Johnson. Both used attenuated cold viruses to transport the vaccine through the body. Instead of the code of the corona spike protein, the vaccine for the devils is equipped with a molecule carried by the tumor cells. Vaccinated in this way, defense cells are supposed to form in the animals' bodies to fight the cancer. In July last year, Flies received permission to test his vaccine.

It has now been shown that the tests have already been successful in captive specimens. This means that the animals have developed an immune response against the tumors. But the road to the wild is long and has its pitfalls: Because it is simply impossible to vaccinate every single devil by injection. Instead, the vaccine is to be packaged in appetizing baits, following the example of rabies vaccinations in Europe and the USA - but these cannot simply be laid out in large areas in the wild. Flies' team therefore relies on snack vending machines. They are designed to attract the animals and only release bait on contact, as if at the touch of a button. To prevent too many treats from ending up in a devil's stomach, the machine initially stops responding after an ejection so that the animals lose interest in the device. "We will soon try out these prototypes and then test ten new dispensers in order to test them in the wild - initially with bait without vaccine," says Flies.

He knows that his vaccine will not prevent cancer. "In the long term, we want to ensure that vaccinated devils survive longer than unvaccinated animals," says Flies. Because more time means more opportunity to mate, i.e. to strengthen the populations. Conservation biologist Carolyn Hogg from the University of Sydney in Australia told the journal Scientific American that it would be enough if the vaccine only partially protected the devils from DFTD. "It just needs to help them live longer than they currently do," says Hogg. "If they live longer, they manage more mating seasons." In future, Flies wants to intelligently upgrade his snack machines with cameras and computers. They should only eject the bait when a Tasmanian devil has actually pressed the button and not another roaming animal.

Meanwhile, it turns out that the disappearance of the Tasmanian devil is already changing the ecosystem. With its decline, the population of all those animals that also feed on carcasses and carrion is increasing. For example, the number of giant pouched martens(Dasyurus maculatus) is increasing. The new conditions are even reflected in its genes, said Andrew Storfer, evolutionary geneticist at Washington State University, in the journal "Nature". He and his team found that genes that control muscle development, for example, were linked to the population density of Tasmanian devils. At least this is very easy to understand: In areas where the marsupial devil has already been killed off, the giant marsupials have to move around far less to find enough food.

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