Entry for:The Peer Prize for Women in Science 2017
1. Please give a brief summary of your work.
Our goal is to save the Tassie devil’s parasites. Everyone wants to save the Tasmanian devil but will it survive for the long haul without the suite of bugs that has lived with it for millions of years? That’s our focus. People generally assume parasites are bad due to their ability to cause disease, but they also have many beneficial roles to play.
We compared communities of the parasites Cryptosporidium and Giardia in wild and captive Tasmanian devils and found that parasite numbers were significantly higher in wild devils than those in captivity. These findings have implications for how we re-introduce captive Tasmanian devils back into the wild, to ensure both they and the populations they are joining have the best chance of survival. We also found human-associated parasites in the devils, indicating the extent of the human footprint to our threatened wildlife.
2. Describe your approach and broader findings.
Tasmanian devil numbers have been decimated by devil facial tumour disease, an ‘infectious cancer’ that has spread across 85 per cent of the range of devils in Tasmania. A massive effort has gone into saving the devils and now that effort is being extended to their parasites. We believe that our research will contribute to the long-term success of the save the devil effort.
Parasites can be good for you, despite being better known for their ability to cause disease and the negative connotations the word conjures. Parasites aren’t typically recognised for their beneficial influence on their host’s immunity, which drives the evolution of both host and parasite, and enables their hosts to combat other diseases. Nor are parasites recognised for their crucial role in maintaining healthy ecosystems and contributions to biodiversity.
The relationship between parasites and their hosts can be highly specific, some hosts are the sole ecosystem for some parasites. So, what is happening to the Tasmanian devil’s parasites given the animal is endangered? Is threatened species management of the Tassie devil impacting their parasites’ life cycle? And what impact are humans having when they encroach on the habitats of Tasmanian devils? These are the questions our team have been asking as part of the Save the Tasmanian Devil Program, which is working to ensure the Tassie devil and its parasites don't become extinct.
Our first study describes prevalence and diversity of the protozoan parasites Cryptosporidium and Giardia in Tasmanian devils. Both parasites have direct life-cycles with environmentally robust infective stages passed in faeces of an infected individual. Water acts as a vector for transmission and human outbreaks are often associated with contaminated swimming pools and drinking water. Species identification within both genera is only possible though molecular techniques and host specificity can be used to infer transmission sources.
We tested faecal DNA (n = 216) from captive and wild devils using parasite specific PCR protocols followed by DNA sequencing to identify species within a phylogenetic framework. Prevalence of both Cryptosporidium and Giardia were significantly higher in wild Tasmanian devils compared to captive devils (p < 0.05); Cryptosporidium and Giardia prevalence was 37.9% and 24.1% respectively in wild devils compared to 10.7% and 0.82% in captive devils.
Molecular analysis revealed three known Cryptosporidium species; The marsupial specific C. fayeri, and C. muris and C. galli which are associated with rodents and birds. For Giardia, strains that associated with humans were identified in captive devils. Novel genotypes of both parasites were identified in captive and wild devils.
The lower prevalence of both Cryptosporidium and Giardia in captive devils compared to wild devils suggests that captive management may be changing host-parasite interactions. The identification of species associated with humans indicates the potential for parasites to move between these hosts and flags consideration for non-DFTD disease risk management. The discovery of novel parasites require further data to determine if they are only found in devils and may also be endangered.
3. What is the wider contribution, or impact, to your scientific field(s)?
1. Our discoveries are helping better inform how to move Tasmanian devils between breeding facilities and captive and wild sites, because when we move the devils we’re also moving their parasites. Our data is helping us better understand what disease risks might be present for both the devils we are moving and the populations they are joining, so that we can minimise these risks and keep the devils healthy.
2. We’ve made the workplace safer for conservation staff by identifying parasites in devils that could be transmitted to humans. Knowing about these risks reduces the possibility of disease transmission between both the devils and their human carers.
3. The lessons from our project could be used to educate and inform the public about the global issue of emerging disease. Humans play a significant role in transmitting pathogens on local and global scales and many iconic animals are threatened by pathogens we can transmit. The Tasmanian devil is a nationally recognised species and it could become a model species for public education on disease.
4. The Save the Tasmanian Devil Program is an extremely successful conservation program. It’s the only conservation project we know of which cares about the parasite and the host. Generally, conservation programs focus on habitat, genetic diversity and increasing numbers with less emphasis on disease risks. Our approach offers a model of a threatened species recovery program to other conservation programs both in Australia and internationally.
5. Parasites aren’t cute, but they’re important to conserve. Efforts to conserve threatened species are typically directed towards the more iconic and larger charismatic species. Our outcomes directly contribute to maintaining diverse representatives of Australia's unique biodiversity and describing biodiversity with the discovery of new parasite species.
4. Are there any potential ideas you would like to explore to take this research further?
Our initial research has discovered novel genetic variants of both Cryptosporidium and Giardia parasites, however we need to acquire more data to complete new species descriptions and define host specificity. We will isolate parasite stages from devil scats, perform morphometrics and additional genetic analyses, and test quolls and other wildlife to determine parasite host range.
We aim to develop genetic tests to search for a rare parasitic helminth found in devils, Daysurotaenia robusta. We will expand our team through the addition of Leslie Chisholm (South Australian Museum) and work with archived parasite material from Tasmanian devils.
Eradicating parasites through anthelmintic treatment is often used by conservation programs. This practice is thought to benefit the animals and improve health. We wish to test the consequences of anthelmintic treatment of devils in captivity and aim to move from traditional single host- single parasite studies to begin to address how co-infecting agents influence each other. Specifically, we wish to ask what happens with co-infecting agents when the worms are removed.
We have also begun studies on bacterial actions in devils. This work is examining the occurrence of human associated bacteria in devils. We ultimately want to examine how interactions between the endemic parasites and bacteria of devils and the invasive human-associated parasites impact devil health. Eventually we will be able examine associations between parasite and endemic symbionts, the genetic diversity of devils themselves and relationship between infectious cancer and co-infection with other agents.
We also look forward to expanding expertise in our fields by training new students in cross-disciplinary projects. We aim to ensure that students generate research outputs and receive recognition for their work. The two papers by Liana Wait and pending third after only a year of study, is a testament to the strength and dedication of Power, Peck and Fox in mentoring future scientists.
5. Please share a link for researchers to access a relevant publication, data-set, or thesis.
Article Source: Molecular characterization of Cryptosporidium and Giardia from the Tasmanian devil (Sarcophilus harrisii) Wait LF, Fox S, Peck S, Power ML (2017) Molecular characterization of Cryptosporidium and Giardia from the Tasmanian devil (Sarcophilus harrisii). PLOS ONE 12(4): e0174994. https://doi.org/10.1371/journal.pone.0174994
We are four female scientists who care about Tasmanian devils and their parasites. We have diverse skills encompassing parasitology, wildlife ecology and veterinary medicine. Liana Wait is a po...