Why are Tasmanian Devils dying from oral cancer?

Before we get into this ailment, let us understand what these Tasmanian devils are - a Tasmanian devil is a well-built marsupial with a large head and powerful jaws; they have black fur and they are not found anywhere else in the world except in Tasmania. They are lethargic and slow-moving but aggressive and feed mainly on carrion. The Tasmanian devil is the world’s largest living carnivorous marsupial. It is about the size of a small dog, Tasmanian devils are well known for their piercing nocturnal shrieks and their strong jaws. They are found only on the island of Tasmania, to the south of the mainland of Australia. Being marsupial mammals, Tasmanian devils give birth to tiny and underdeveloped young, completing their development in the mother’s pouch. The Devil Facial Tumour Disease (DFTD) is a distinctive form of transferable cancer which harms its victims by causing tumours to grow around the face. These tumours interfere with their feeding patterns and lead ultimately to starvation. The lack of genetic variation in Tasmanian devil population leaves them particularly vulnerable to mass infection. Hence, the disease has eradicated a large percentage of Tasmanian devils, inflicting havoc in the survival of this already endangered species. Perhaps no animal is better suited to its name than the Tasmanian devil. While it might look cuddly; in reality, this animal is quite the opposite. With the strongest bite of any mammal and a wicked blood-curdling scream, the Tasmanian devil is a ferocious creature which is known to assault animals many times its size. The irony is that even this devil is no match for its supreme enemy - an unusual and contagious face cancer, wrecking the population. The first glimpse of this mysterious disease was given about two decades ago when people sighted large tumours on Tasmanian devils’ faces. They began to grow common. The news channels then started reporting that in the past twenty years; a third of their population had already died from this mysterious illness. The tumours were growing at a rapid and uncontrollable rate until they were noticed. The tumours were slowly covering their mouths and eyes and were giving indication that this could be cancerous. Neither the people living in Tasmania were able to figure nor were the scientists there able to determine the cause of such large tumours that were pervasive and growing fast. Usually, cancer starts as a result of a single mutation or a change to a section of DNA (Deoxyribonucleic Acid). Most mutations are safe but often; they can cause a cell to grow and divide in an uncontrollable manner. This unrestricted enlargement causes the rogue cells to amass, forming the masses that we recognise as cancerous tumors. As cancer cells continually grow and divide, they tend to get more and more mutations in their DNA, resulting in tumors that give birth to a broader landscape of mutations. However, as mutations are considered random events, cancer often looks different in each individual. For example, two people having breast cancer may have tumors with completely different armoury of mutations. This is what makes the case of the Tasmanian devil so puzzling. It is almost impossible for so many of these animals to independently develop similar type of cancer so quickly through the classical mutation technique. Even more intriguing is that every tumor sample has shown the same pattern of alterations in the Tasmanian devils’ chromosomes. This finding was quite odd, especially compared to how cancer has been generally shown to appear through a series of random mutations to DNA. The fact that all Tasmanian devil samples showed the same irregular chromosome patterns made researchers suspect that the devils were not suffering from a typical type of cancer as it would be nearly impossible for so many creatures to grow with the same exact mutations in their DNA. Instead, the lethal cancer spreading through their population might be infectious, spreading from one animal to another through bites to the face during sessions of fighting. Intriguingly, the cancer affecting the Tasmanian devils showed no sign of viral transmission and the similarity among tumors did not support the mutation model. How this is then spreading from one animal to another? The answer may lie in what is called the MHC or Major Histo-compatibility Complex. The immune system has various ways of protecting the body against invasion by viruses, bacteria and parasites and any intrusive or cancerous cells. The first line of defense is built up by an inborn immune response made up of barriers like skin, tears, saliva and mucus. This is followed by defensive mechanisms built up by adaptive immune reactions that are more specific for the intruder. Adaptive immunity includes both a humoral response (macro-molecules) produced by antibodies and a cell-mediated reaction produced by T-cells that have the ability to destroy other cells. The cell-mediated adaptive immune reaction is synchronised by the Major Histo-compatibility Complex (MHC). It is called that because it is responsible for the rejection of graft or tissue compatibility. As per reports, compared with the figures of Tasmanian devils in the past decade, almost sixty percent of their population has been destroyed by this disease. From the time of the initial discovery of DFT1, a second mutation has arisen as a variation in the form of DFT2 and has been devastating their population. There is a very fine article written by Sharon Guynup in Mongabay magazine, which will help throw up better light on this issue facing the Tasmanian devils. Here is the link: https://news.mongabay.com/2021/10/in-harms-way-our-actions-put-people-and-wildlife-at-risk-of-disease/. This article elaborates on facts like how infectious diseases such as these pose a grave threat to not only Tasmanian devils but also chimpanzees, tigers, African wild dogs and Ethiopian wolves. Some viral diseases are being spread by humans, other domestic animals and livestock and this can culminate in giving a knockout punch to already endangered species that are bordering on extinction’s edge. Not many people realize that a collection of humans, pigs, cows, dogs or chickens into wild areas can bring in further risk of the already endangered species. Somewhere along the line, man has had a broken relationship with nature in its wild patches. Corporate greed has also proved that the rich are quite separate from the rest of the species on earth. Activity of rich corporate thinkers has altered natural systems on earth in a rapid way. It has been so dramatic in the last few decades that it has brought in a new geological eon. These changes include deforestation which has gone out of control, farming, ranching, international travel, global commerce and wildlife trade with the help of poachers has affected climate change and has also helped spread diseases. Why does this happen? It is because such activities bring livestock, people and wildlife into contact, exposing all concerned to viruses and bacteria. Often, the ones suffering lack immunity in a rapidly warming world. Ticks, mosquitoes and several other parasitic carriers of diseases have an expanded range now, bringing debilitating ailments along with them. These changes have also helped new diseases to appear and spread to newer areas. This may lead perhaps to outbreaks soaring in the future. We have already seen recently how a pandemic could impact the whole ecosystem of this planet. Paradoxically, the ecosystem benefits when the dark satanic mills run to less than their optimal range and people are not polluting the atmosphere with carbon monoxide. Here is the ominous part! Roughly around seventy per cent of all the growing and re-emerging pathogens are becoming zoonotic diseases that are transmitted from animals to humans. We have no idea when the next threat or the next Disease X will strike and when. This is also the sentiment shared by the Director of the World Health Organisation, Tedros Adhanom Ghebreyesus when he voiced the same at a meeting concerned with global animal health. Most infectious viruses are emerging from tropical areas which are also home to a rich variety of species and the volume of pathogens they can host and these areas are China, parts of Southeast Asia, Africa and India. We simply have to face the fact that we have to live with diseases as they have become a part of this natural world. Bacteria and viruses have become interwoven into our ecosystems in a varied environment where indigenous residents have now evolved immune systems which prevent high rates of infection and subsequent deaths. Ecosystems have become intact and they maintain equilibrium. For example, as per Rick Ostfeld, a disease ecologist at Cary Institute of Ecosystem Studies in Millbrook, New York, USA, the web of life is thriving in tropical forests and also keeping hosts of diseases like rodents in decent check. Coming back to our main focus, the Tasmanian devil facial tumour disease involves a couple of independent transmissible cancerous cells which have killed a majority of these species. These cells are originating from Schwann cells and spread between them as they bite each other as that is a common kind of behaviour during their mating season. DFT1 and DFT2 spread as a result of direct contact between them in situations involving fights over food and mates. It is a point to be noted that like most other cancer remedial care, there is no satisfactory treatment procedures for DFT1 and DFT2. Several chemotherapeutic medicines have been on trial for DFT1 but not even one has shown any real efficacy towards treating this disease. Preliminary trials of immunotherapy have shown better promise in case of DFT1. So, what is actually been done to save these Tasmanian devils. The government of Australia has started a funded initiative with the aim of saving this species. Research is being directed that will help understand the cause of these growing tumours. The main objective is to develop a vaccine; and if not, at least some form of intervention or therapy.