Amphibian chytrid fungus: impacts on Australian frogs and ongoing conservation challenges

Amphibian chytrid fungus: impacts on Australian frogs and ongoing conservation challenges

Hot Topics in Ecology

Amphibian chytrid fungus: impacts on Australian frogs and ongoing conservation challenges

Ben C. Scheele, Threatened Species Recovery Hub, Fenner School of Environment and Society, The Australian National University, Canberra ACT 2601, Australia, Laura F. Grogan, Environmental Futures Research Institute, Griffith University, Nathan QLD 4111, Australia, Thais Sasso, School of Environment, Science and Engineering, Southern Cross University, Lismore NSW 2480, Australia

Since the mid-20th century, the human-facilitated spread of the fungal skin disease, chytridiomycosis (caused by Batrachochytrium dendrobatidis; chytrid fungus), has contributed to the decline of 501 amphibian species, including 90 presumed extinctions globally. In Australia, chytridiomycosis has contributed to the decline of 43 frog species, including seven presumed extinctions. The earliest detection of chytrid fungus in Australia is from 1978 near Brisbane. Chytrid fungus spread north and south, causing frog declines along the eastern ranges and in Tasmania; it is not associated with declines in Western Australia or the arid /semi-arid zone, and is intolerant of desiccation and temperatures >28oC. Outbreaks can cause rapid population declines, but chytrid fungus also persists in frog communities and can have long-term impacts. Frog communities can include tolerant hosts (species, or life-stages such as tadpoles, that can harbor the fungus without suffering disease) co-occurring with more susceptible species or life stages. These hosts can maintain high infection rates in susceptible individuals. This process can lead to the decline or extinction of species decades after initial outbreaks. Chytrid fungus remains a threat for Australian frogs, with eradication unlikely. Ongoing mortality is common in impacted species. There is limited evidence for protective immune responses or the evolution of resistance or tolerance to infection in susceptible species. Preventing further extinctions requires improved biosecurity and the development of effective mitigation. Potential strategies include increasing an individual’s capacity to withstand infection (e.g. probiotics), reducing environmental suitability for chytrid fungus (e.g. altering water salinity), or reducing other threats (e.g. increase breeding and survival to outweigh deaths caused by the disease). Investment is needed to develop and implement such strategies.

Hot Topic Lead Author: 
Name: Ben Scheele
Email: ben.scheele@anu.edu.au
Phone: 03 9244 5239

Date approved: 
Friday, November 1, 2019 - 10:46
ID Title Location Type
10256 Murray K. A., Retallick R. W. R., Puschendorf R., Skerratt L. F., Rosauer D., McCallum H. I., Berger L., Speare R. & VanDerWal J. (2011) Assessing spatial patterns of disease risk to biodiversity: Implications for the management of the amphibian pathogen, Spatial environmental suitability modelling paper
10257 Berger L., Speare R., Daszak P., Green D. E., Cunningham A. A., Goggin C. L., Slocombe R., Ragan M. A., Hyatt A. D., McDonald K. R., Hines H. B., Lips K. R., Marantelli G. & Parkes H. (1998) Chytridiomycosis causes amphibian mortality associated with popu Epidemiological examination of wild collected specimens and a transmission experiment
10258 Scheele B. C., Skerratt L. F., Grogan L. F., Hunter D. A., Clemann N., McFadden M., Newell D., Hoskin C. J., Gillespie G. R. & Heard G. W. (2017) After the epidemic: Ongoing declines, stabilizations and recoveries in amphibians afflicted by chytridiomycos Review paper
10259 Skerratt L., Berger L., Clemann N., Hunter D., Marantelli G., Newell D., Philips A., McFadden M., Hines H., Scheele B., Brannelly L., Speare R., Versteegen S., Cashins S. & West M. (2016) Priorities for management of chytridiomycosis in Australia: saving Review paper
10260 Full reference
10261 Aim
10262 Type of Study
10263 Key Results
10264 Recommendations
10265 Ecosystem and location
10266 Reviewer
10267 Scheele B. C., Hunter D. A., Brannelly L. A., Skerratt L. F. & Driscoll D. A. (2017) Reservoir‐host amplification of disease impact in an endangered amphibian. Conserv. Biol. 31, 592-600.
10268 To (1) determine via laboratory experiment and field surveys whether Crinia signifera is a potential reservoir host for chytrid fungus, (2) determine via field surveys whether C. signifera presence associates with increased chytrid fungus prevalence in sy
10269 Laboratory experiment and field surveys
10270 Reservoir species can promote declines of susceptible sympatric species through pathogen-mediated apparent competition. Crinia signifera was found to be a reservoir species for chytrid fungus - they maintained infection for 12 weeks without disease-associ
10271 Sites lacking reservoir hosts may provide important refugia. Identifying reservoir hosts and mapping their distributions will assist in identifying such refugia.
10272 Frost-hollow grasslands, narrow seeps and open bogs in temperate highlands of southeastern Australia.
10273 Laura Grogan
10274 To review and compare the importance of key theoretical and empirically demonstrated mechanisms promoting disease-associated declines and extinction of natural populations. The presence of reservoirs (biotic or abiotic) is one of the most commonly cited factors for disease-induced extinction in empirical studies. Multi-host pathogens with differential pathogenicity between host species can drive the decline or extinction of one or more of these species, while other species act as reservoirs or carriers.
10233 de Castro F. & Bolker B. (2005) Mechanisms of disease-induced extinction. Ecol. Lett. 8, 117-26. Review paper
10234 Grogan L. F., Robert J., Berger L., Skerratt L. F., Scheele B. C., Castley J. G., Newell D. A. & McCallum H. I. (2018) Review of the amphibian immune response to chytridiomycosis, and future directions. Front. Immunol. 9, 2536. Review paper
10235 Blaustein A., Urbina J., Snyder P., Reynolds E., Dang T., Hoverman J., Han B., Olson D., Searle C. & Hambalek N. (2018) Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies. Diversity 10, 81. Review paper (reviews manipulative experimental studies)
10236 Murray K. A., Retallick R. W. R., Puschendorf R., Skerratt L. F., Rosauer D., McCallum H. I., Berger L., Speare R. & VanDerWal J. (2011) Assessing spatial patterns of disease risk to biodiversity: Implications for the management of the amphibian pathogen, Spatial environmental suitability modelling paper
10237 Rachowicz L. J. & Vredenburg V. T. (2004) Transmission of Batrachochytrium dendrobatidis within and between amphibian life stages. Dis. Aquatic Org. 61, 75-83. Laboratory exposure experiment and cross-sectional field surveys
10238 Raberg L., Graham A. L. & Read A. F. (2009) Decomposing health: tolerance and resistance to parasites in animals. Philos. Trans. R. Soc. B-Biol. Sci. 364, 37-49. Review paper
10239 Savage A. E. & Zamudio K. R. (2016) Adaptive tolerance to a pathogenic fungus drives major histocompatibility complex evolution in natural amphibian populations. Proc. R. Soc. B Biol. Sci. 283. Field surveys and sampling combined with MHC genotyping and analysis
10240 Wilber M. Q., Knapp R. A., Toothman M. & Briggs C. J. (2017) Resistance, tolerance and environmental transmission dynamics determine host extinction risk in a load-dependent amphibian disease. Ecol. Lett. 20, 1169-81. Laboratory exposure experiment, mesocosm transmission experiment, and integral projection modelling
10241 Berger L., Speare R., Daszak P., Green D. E., Cunningham A. A., Goggin C. L., Slocombe R., Ragan M. A., Hyatt A. D., McDonald K. R., Hines H. B., Lips K. R., Marantelli G. & Parkes H. (1998) Chytridiomycosis causes amphibian mortality associated with popu Epidemiological examination of wild collected specimens and a transmission experiment
10242 Richards S. J., McDonald K. R. & Alford R. A. (1993) Declines in populations of Australia's endemic tropical rainforest frogs. Pac. Conserv. Biol. 1, 66-77. Monitoring and survey of frog occurrences
10243 Hoskin C. J., Hines H. B., Webb R. J., Skerratt L. F. & Berger L. (2019) Naïve rainforest frogs on Cape York, Australia, are at risk of the introduction of amphibian chytridiomycosis disease. Aust. J. Zool. 66, 174-8. Sampling of frogs from Cape Melville for chytrid fungus
10244 Scheele B. C., Hunter D. A., Grogan L., Berger L., Kolby J., McFadden M., Marantelli G., Skerratt L. F. & Driscoll D. A. (2014) Interventions for reducing extinction risk in chytridiomycosis-threatened amphibians. Conserv. Biol. 28, 1195–205. Conceptual paper
10245 Scheele B. C., Skerratt L. F., Grogan L. F., Hunter D. A., Clemann N., McFadden M., Newell D., Hoskin C. J., Gillespie G. R. & Heard G. W. (2017) After the epidemic: Ongoing declines, stabilizations and recoveries in amphibians afflicted by chytridiomycos Review paper
10246 Skerratt L., Berger L., Clemann N., Hunter D., Marantelli G., Newell D., Philips A., McFadden M., Hines H., Scheele B., Brannelly L., Speare R., Versteegen S., Cashins S. & West M. (2016) Priorities for management of chytridiomycosis in Australia: saving Review paper
10247 Scheele B. C., et al. (2019) Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity. Science 363, 1459-63. Review paper
10248 Becker, G. & Zamudio,K. R. (2011) Tropical amphibian populations experience higher disease risk in natural habitats. Proceedings of the National Academy of Sciences,108. Field data
10249 Heard G.W., Scroggie M.P., Clemann N., Ramsey D.S.L. (2014) Wetland characteristics influence disease risk for a threatened amphibian. Ecological Applications,24. Field survey applying mark-recapture data and simulations
10250 Kriger, K. M., Pereoglou, F., Hero, J. M. (2007) Latitudinal variation in the prevalence and intensity of chytrid (Batrachochytrium dendrobatidis) infection in eastern Australia Conservation Biology,21. Field survey
10251 Pauza M.D., Driessen M.M., Skerratt L.F. (2010) Distribution and risk factors for spread of amphibian chytrid fungus Batrachochytrium dendrobatidis in the Tasmanian wilderness world heritage area, Australia. Diseases of Aquatic Organisms,92. Observation in the field
10252 Puschendorf, R., Hoskin. C.J., Cashins, S.D., Mcdonald, K., Skerratt, L.F., Vanderwal, J., Alford, R. (2011) Environmental refuge from disease-driven amphibian extinction. Conservation Biology,25(5):956–64. Field survey
10253 Stockwell, M.P., Bower, D.S., Bainbridge, L., Clulow, J., Mahony, M. J. (2015) Island provides a pathogen refuge within climatically suitable area. Biodiversity conservation,24(10):2583–92. Field survey
10254 Stockwell, M.P., Clulow, J., Mahony, M.J. (2015) Evidence of a salt refuge: chytrid infection loads are suppressed in hosts exposed to salt. Oecologia,177(3):901–10. Field survey and laboratory experiments
10255 Woodhams, D. C., Alford, R. A. (2005) Ecology of chytridiomycosis in Rainforest stream frog assemblages of Tropical Queensland. Conservation Biology,19. Field survey