If luck in the animal kingdom exists, its almost certain that Tasmanian Devils don’t have it. You are probably aware the conservationists have been struggling in a battle to save these endangered marsupials against disease, as their battle against facial tumours is a relatively high profile one. However whilst vaccines are being diligently developed in an attempt to save wild populations, another blow has been dealt to Tasmanian devils. It’s not just one cancer they are suffering from.
To understand the extinction threat faced by Tasmanian Devils we need to travel back to 1996. In the North-East of Tasmania the first case of devil facial tumour disease (DFTD) was spotted and started to spread. Each year the disease spread further and killed more individuals as tumours erupted on their faces making it difficult for them to eat. A devil with visible signs of DFTD has a few months left to live.
Although the spread of DFTD was consistent with that of an infectious disease, we now know that it is actually a cancer. This is where the Tasmanian devils bad luck becomes apparent; they are suffering from one of only four known contagious cancers. If you’re interested in the nitty gritty science behind the cancer this article on The Consversation gives a good explanation.
In brief, the infected Tasmanian Devils spread the cancer (DFTD) through biting, a behaviour common amongst the species. Tasmanian Devils typically bite each other when fighting for food and during mating, which leads to the transmission of the cancer. This has resulted in nearly all sexually mature males in diseased areas becoming infected and has changed the dynamics of the population.
You’re probably thinking it’s not sounding great for Tasmanian Devils. Unfortunately according to a study published last week in the journal Proceedings of the National Academy of Science their luck isn’t about to change. A second cancer has been detected in the species, which although visually no different to the original cancer it has been proven to be genetically different.
First discovered in 2014, the cancer is now known to have spread to eight individuals in the South-East of Tasmania. Elizabeth Murchison from the Department of Veterinary Medicine at the University of Cambridge, claims this may be evidence that contagious cancers are not as rare in nature as previously thought.
“Previously, we thought that Tasmanian devils were extremely unlucky to have fallen victim to a single runaway cancer that emerged from one individual devil and spread through the devil population by biting,” she said. “However, now that we have discovered that this has happened a second time, it makes us wonder if Tasmanian devils might be particularly vulnerable to developing this type of disease, or that transmissible cancers may not be as rare in nature as we previously thought.”
It is currently unclear why Tasmanian Devils could be particularly susceptible to transmissible cancers, however one theory is that their low genetic diversity may play a role. The Tasmanian Devil population may be so genetically similar that individuals immune systems cannot recognise the foreign tumour cells which have to invade their body for the cancer to spread.
Whilst this may all seem very bleak, it should be noted that scientists are working on a vaccine to help save Tasmanian Devils. Of course this vaccine may now need an update to include the prospect of multiple cancer strains.
Featured Image From WikiCommons:KeresH
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