About Platypus Fungal Disease
The platypus (Ornithorhynchus anatinus
) is the last surviving species of a number of platypus-like ancestors that existed on the super continent of Gondwanaland over 100 million years ago, when dinosaurs roamed the earth1
. Some scientists feel that platypus are now so specialised, and so far out on the evolutionary tree, that they are vulnerable to environmental change. Certainly they are dependent on aquatic habitats for their survival, and may be susceptible to a range of environmental changes arising from human activities2
Platypuses generally suffer from few diseases in the wild3
, however there is widespread public concern in Tasmania about the potential impacts of a disease caused by the fungus
. This platypus fungal disease (termed Mucormycosis) only affects Tasmanian platypuses, and has not been observed in over 2000 platypuses captured in mainland Australia4
. Affected platypuses can develop ugly skin lesions or ulcers on various parts of the body including their backs, tails and legs.
Dorsal ulcer on platypus
Photo: Josh Griffiths
Platypus with ulcer on hind leg
Photo: Nick Gust
Close up of ulcer on foreleg
Photo: Nick Gust
These photos were taken in north central Tasmania and show platypuses with ulcerated lesions caused by Mucormycosis.
This fungal disease can kill platypuses5
, with death arising from secondary infection and by affecting the animals' ability to maintain body temperature and forage efficiency.
It is an unfortunate coincidence that one of Tasmania's other iconic mammals, the Tasmanian Devil, is also suffering from a disease. Platypus Mucormycosis and
Devil Facial Tumour Disease
both cause ugly deformities and can kill the infected animals. However these diseases are caused by different pathogens. Devil Facial Tumor Disease is taking a heavy toll on Tasmanian devil populations, but we do not yet know what impact Mucormycosis is having on platypus populations.
History of platypus fungal disease
Mucormycosis disease was first observed in platypuses in 1982 in the Elizabeth River near Campbell Town in the north of Tasmania6
. However it wasn't until 1993 that the causative agent
was positively identified
is a native Australian fungus previously restricted to mainland Australia (in particular northern New South Wales and Queensland). On the mainland it is known to infect and kill frogs and toads7
. Recent research indicates the positive mating strain of this fungus present in Tasmanian platypuses is particularly virulent8
. It seems likely that the fungus was introduced to Tasmania via infected frogs transported from mainland Australia. Further speculation exists that the fungus arrived via green tree frogs amongst banana shipments from Queensland. However it could also have arrived via the illegal introduction of frogs as pets into the State. We will never know for sure.
Since 1982, the disease seems to have spread in Tasmanian platypus populations. It is now known to infect platypuses in a variety of locations through the north central part of the state including the Supply, Meander, Liffey, South Esk and Elizabeth rivers, and Brumby's creek.3,4,5,6
Additional anecdotal reports of diseased platypus in southern and north-western river systems have fuelled fears the disease may be spreading, and may impact platypus populations in other parts of Tasmania including the Tasmanian Wilderness World Heritage Area.
Known historical distribution of diseased platypus in Tasmania from 1982 to 2007
Blue points indicate locations where apparently healthy platypuses have been recorded, red points indicate confirmed cases of Mucormycosis, orange indicates ulcerated platypuses likely to be caused by Mucormycosis, and yellow indicates sightings of possibly diseased platypuses.Click on the image for a larger view.
How is the Disease Spread?
We don't know yet.
An unusual feature of this disease is that it affects platypuses only in Tasmania and not on the Australian mainland where the same pathogen infects frogs and toads. Although amphibians are susceptible to this fungus, and are likely to be the vector for originally transporting the pathogen to Tasmania, there are no records of Tasmanian frogs infected with the fungus. We do not know yet how the disease is spread amongst platypuses. A number of potential vectors exist that could possibly be transmitting the disease in Tasmania. Determining how the disease is spread, and what the vectors are is an area of renewed research involving collaboration between a number of Tasmanian ecologists, vets, and disease researchers.
What Effect is the Disease Having on Platypus Populations?
Platypuses are currently considered common and widespread in Tasmania, although they are potentially vulnerable to a number of human-mediated changes to their environment9
Mucormycosis may represent one of the most significant threats both to the health of individuals, and persistence of platypuses in the 100 years since they were first protected in Tasmania in 1907. However, we currently lack fundamental information on the epidemiology of the disease to interpret the magnitude of threat.
For instance although the disease has previously been confirmed from a series of rivers in north and central Tasmania, limited sampling means it is currently unclear how far Mucormycosis has already spread, or how fast it is spreading around Tasmania. It is a major concern for the conservation of this unique species that so little is known about the impact and significance of Mucormycosis fungal disease.
At the moment we are not sure how Mucormycosis disease affects the abundance or distribution of platypuses in Tasmania. Determining the impact of the disease is an important focus of this research program and involves collaboration amongst a series of researchers across two Tasmanian government departments and two Australian universities. We are currently collecting baseline information on the spatial extent of the disease, proportion of platypuses infected within the range of the fungus, the fate of diseased individuals and their survival prospects once infected. We require fundamental information on how the disease adversely impacts platypus numbers, or whether there are detectable effects on population densities or demographics. Indeed the broad impacts at a population level are yet to be quantified, with the result that platypus numbers may well have declined in parts of Tasmania where the disease occurs.
1. Grant T, Fanning D. 2007. Platypus. Fourth edition. CSIRO publishing: Australian Natural History Series. 157 pages. (available from www.publishing.csiro.au)
2. Long J, Archer M, Flannery T, Hand S. 2002. Prehistoric mammals of Australia and New Guinea: one hundred million years of evolution. Sydney: University of NSW Press.
3. Munday BL, Whittington RJ, Stewart NJ. 1998. Disease conditions and subclinical infections in the platypus (Ornithorhynchus anatinus). Transactions of the Royal Society of London Series B 353:1093-1099.
4. Connolly JH, Obendorf DL, Whittington RJ, Muir DB. 1997. Causes of morbidity and mortality in platypus (Ornithorhynchus anatinus) from Tasmania, with particular reference to Mucor amphibiorum infection. Australian Mammalogy 20:177-187.
5. Obendorf DL, Peel BF, Munday BL. 1993. Mucor amphibiorum infection in platypus (Ornithorhynchus anatinus) from Tasmania. Journal of Wildlife Diseases 29(3): 485-487.
6. Munday BL, Peel BF. 1983. Severe ulcerative dermatitis in platypus (Ornithoryhchus anatinus). Journal of Wildlife Diseases 19(4): 363-365.
7. Speare R, Thomas A, O'Shea P, Shipton W. 1994. Mucor amphibiorum in the toad (Bufo marinus) in Australia. Journal of Wildlife Diseases 30: 399-407.
8. Stewart, N. J. and B. L. Munday (2005). 'Possible differences in pathogenicity between cane toad-, frog- and platypus-derived isolates of Mucor amphibiorum, and a platypus-derived isolate of Mucor circinelloides.' Medical Mycology 43(2): 127-132.
9. Grant TR, Temple-Smith PD. 2003. Conservation of the Platypus, Ornithorhynchus anatinus: Threats and Challenges. Aquatic Ecosystem Health & Management 6(1): 5-18.