Saving our Tassie Devils: new insights in fight against contagious cancers

Ecological Society of Australia
  • Closing in on a blood test diagnosis
  • How baits could be used to deliver vaccines
  • Devils fighting off their own tumours
  • Infected populations growing up too fast
  • How devils protect threatened species from feral cats
  • And why the boys are to blame.
  • At the University of Tasmania, they are working on a diagnostic blood test, over at the Menzies Institute they’re looking to learn from the treatment of rabies and hoping to develop a vaccine delivered by delicious oral baits.

    But surprisingly, and encouragingly, researchers have also been observing natural regressions of the tumours in wild populations of Tasmanian Devils, without any human intervention.

    Twenty years since contagious facial tumours were first discovered in Tasmanian Devils, and five years since a second type of tumour appeared, experts from Australia, the USA and France are gathering at the Ecological Society of Australia Conference in Launceston to compare strategies on how best to save the Tassie Devil.

    “This is such a big, complex problem, we have people with expertise in genomics and genetics, people with expertise in immunology, and veterinary science, disease ecologists and epidemiologists all working on this problem, from around Australia and around the world,” says Dr Rodrigo Hamede, one of the symposium organisers from the University of Tasmania.

    Complete eradication of the first type of devil facial tumour disease (DFTD) is currently not a feasible as it is widespread throughout Tasmania. However, the second type of devil facial tumour disease (DFT2) is still confined to a small geographic region, so the researchers are working together to come up with contingency plans for long-term devil population management.

    “One of the very interesting things that we’ll be discussing is a preventative vaccine for DFT2, if it’s developed in the future, or the management of the natural resistance that we’ve already seen in devil populations,” says Rodrigo.

    “We have seen more than fifty cases of animals ridding themselves from these tumours without any human intervention and we’ll investigate the genomic bases of those responses, to see whether we can use that information to build resistant populations in the future.”

    Taking the bait: Oral vaccines could help Tassie devils survive tumour diseases

    Andrew Flies (Menzies Institute for Medical Research, University of Tasmania)

    Vaccines in baits have been incredibly successful in rabies control programs around the globe. In this approach animals are vaccinated when they bite into a bait capsule, so it eliminates the need to trap and vaccinate every animal, thus making it effective across large areas.

    Devil facial tumour cells are spread through bites, which is the most common means of rabies transmission in wildlife. Vaccinating the most likely site of devil facial tumour cell infection could provide protection where it is most likely to be needed and prevent tumour cells from taking root in devils.

    The bait vaccine could help devils who are already infected with devil facial tumour cells. This “oncolytic virus” approach was first approved for treating human melanoma in 2015. It works by using a virus to directly kill tumour cells and simultaneously recruit the immune system to the virus and tumours; proper modification of the vaccine helps the immune system to continue killing tumour cells after the virus has been eliminated.

    However, this approach isn’t without its challenges, Andrew and his team warn. For example, researches will need to find the right immune system-triggering molecule unique to the facial tumour cells to ‘teach’ the immune system what to respond to, and they’ll need to figure out how to best distribute the baits so they are eaten by enough devils. Since the second type of devil facial tumour disease is so far only present in a small section of Tasmania, the researchers say they’ll first focus on using the baits to stop its spread or eliminate it.

    Devils protect smaller critters from feral cats

    Calum Cunningham (University of Tasmania)

    Tasmanian Devils could be helping protect threatened species, such as the Southern Brown Bandicoot, by regulating the ecosystem – including feral cat numbers – from the top down, according to a new study by Calum Cunningham at the University of Tasmania.

    Using camera traps, Calum found that areas with high numbers of Tasmanian Devils have lower numbers of feral cats and says this could be contributing to the survival of smaller critters. Southern Brown Bandicoots are similar to many mammals driven extinct by introduced predators and seem to be able to withstand areas with medium cat abundance, but not those with high numbers of cats.

    By also studying the introduction of Tasmanian Devils to Maria Island, Calum says this “natural experiment” is revealing how devils could help restore ecosystems from the top down, helping conserve other threatened species.

    Don’t stand so close to me: mating males key to spread of facial tumours?

    David Hamilton (University of Tasmania)

    Male devils are a key source of bite wounds during the mating season, which spread the deadly facial tumour diseases, according to recent research, led by the University of Tasmania’s David Hamilton.

    The researchers compared the ‘social networks’ of devils both before and after they were infected with the facial tumour disease to find out how the devils’ social lives could contribute to potential transmission, and whether devils change their behaviour after they’re infected.

    David and his team found males during the mating season were especially likely to be bitten, but once devils were infected, they were less likely to interact with other devils. These results could be useful in understanding the transmission process of devil facial tumour disease, say the researchers.

    Also in this session:

    · 20 years of devil facial tumour disease: lessons from an endangered species and an immortal enemy? – Rodrigo Hamede (University of Tasmania and Deakin University)

    · A step closer to a blood test for diagnosing the devil facial tumour diseases – Camila Espejo (University of Tasmania)

    · Better the devil you know: Understanding devil immune systems – Beata Ujvari (Deakin University and University of Tasmania)

    · Devils in infected populations are growing up too fast. Shifts in Tasmanian devil development and life history in response to devil facial tumour disease – Douglas Kerlin (Environmental Futures Research Institute, Griffith University)

    /Public Release.