Our research group investigates the causes and control of infectious diseases in wildlife that impact biodiversity, human health and domestic animal health. The image at the top of the page is by Kolby and was taken while performing chytrid surveillance of the international amphibian trade.
Infectious diseases of wildlife are becoming increasingly important as globalisation and environmental change are causing them to emerge and re-emerge. The One Health Research Group uses a multidisciplinary approach to provide holistic solutions to mitigate their impact (Skerratt et al 2009, Murray et al 2012).
One Health researchers Lee Berger and Rebecca Webb in the lab. Images from Rebecca Webb.
Our major ongoing research activity over the past 20 years has been the discovery and control of one of the major causes of global amphibian decline, chytridiomycosis (Berger et al 1998, Skerratt et al 2007). Other current research includes determining ways to improve the control of transmission of Hendra virus from flying foxes into horses and humans (Mendez et al 2012), assessing the risk of spill over of wild dog zoonoses (Banks et al 2006) and determining the importance of disease in the conservation of the endangered Proserpine rock wallaby and the vulnerable spectacled flying fox. We are also investigating viral diseases in Australian freshwater turtles and agamid lizards. Recent past work includes investigating the causes of avian influenza and Newcastle disease in waterfowl in northern Australia, both these diseases sporadically spill over into poultry (Hoque et al 2011). We advocate a ‘One Health’ approach, especially in regards to zoonoses (Speare et al 2015)
The group provides advice on wildlife health issues to the general public, private companies, state and national governments and international bodies such as the IUCN and OIE. It is a member of the JCU level 1 research centre, Biosecurity and Tropical Infectious Diseases and the Queensland Tropical Health Alliance.
The group members and selected outputs are provided below. Further details of individual researchers’ contact details, full activities, outputs and project grants can be found on their staff web pages.
Amphibian chytrid fungus:
OHRG researchers have been at the forefront of research into amphibian Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). This disease is of major global concern as it has caused extinction of several amphibian species, and the decline of many more.
The fungus infects the outer layers of the frog’s skin, and it was unclear as to why it is so deadly to a broad range of hosts. Our research has shown that infection with Bd causes electrolyte depletion and eventually results in cardiac arrest (Voyles et al 2009, Voyles et al 2007). We have investigated other physiological effects of chytridiomycosis- such as changes to the hematopoietic tissue (liver, spleen and bone marrow) (Brannelly et al 2016), changes in skin cell apoptosis (Brannelly et al 2017) and changes in white blood cells (Young et al 2014, Greenspan et al unpublished).
Evidence suggests that the fungus has been spreading round the globe, causing declines and even extinctions as it moves into new areas with naïve amphibian populations (Skerratt et al 2007). This has highlighted the importance of hygiene measures to prevent further spread of Bd and other amphibian diseases. Our group has developed protocols to minimise exposure of amphibians to pathogens during field studies (Phillott et al 2010) and identified the most effective disinfectants (Johnson et al 2003, Webb et al 2007, Webb et al 2012). International and domestic amphibian trade may also be a mechanism for Chytridiomycosis spread, so we are investigating the prevalence of Bd in Amphibian shipments in the pet and food trade (Kolby et al 2014). We are also interested in how best to treat infected amphibians in a cost effective and safe manner, undertaking clinical trials with a range of antifungal drugs (Brannelly et al 2015, Woodward et al2014, Young et al 2012), while also working to develop a model of the mechanisms underlying absorption through frog skin in order to guide further drug candidate selection.
The fungus cannot be eradicated from the wild, which makes captive breeding & release programs futile unless we can increase the resistance of the animals to the disease. Selective breeding may be the answer, if we can increase the proportion of resistant genes in the population. But first, gene types (alleles) that confer resistance to Bd must be identified. We have characterised the major histocompatibility complex (MHC) class IA gene region in endangered corroboree frogs (Kosch et al 2017) providing the platform to begin breeding frogs with higher resistance to the pathogen.
The One Health Research Group has also been involved studying the ecological effects of Bd. We have found that the emergence of Bd through alpine tree frog populations can dramatically change the age structure, and while the populations persist, the life span of individuals is greatly reduced. This change can make populations more vulnerable to local extinction if adverse environmental conditions prevent a successful breeding season. (Scheele et al 2016, 2017a)
Some less susceptible frog species, such as the common eastern froglet Crinia signifera, can carry Bd without succumbing to the disease. These reservoir species can amplify the disease, causing declines in sympatric species (Scheele et al 2017b, Brannelly et al unpublished)
Hendra virus and veterinarians:
Hendra virus (HeV) is an emerging zoonotic disease which spills-over from flying foxes to horses, and occasionally from horses to humans. The mortality rate in humans is >50%, hence it is a significant concern for horse owners and veterinarians. Our group has been researching the challenges that veterinarians face when communicating to clients the risks relating to HeV (Mendez et al 2017) and adopting recommendations for improved infection control (Mendez et al 2014a, Mendez et al 2014b).
The horse vaccine appears successful (Peel et al 2016), however it remains important to reduce the chance of spill-over. For this reason we have been investigating factors that might influence spill-over events, such as the bioclimatic niche of flying fox species (Martin et al 2016) and the microclimate that the virus faces on the transmission route between flying foxes and horses (Martin et al 2017).
The One Health Research Group has also been investigating the zoonoses of wild and domestic dogs in rural Australian communities. Dogs can act as reservoirs for zoonotic organisms such as Toxocara canis (dog roundworm), Dirofilaria immitis (heart worm), Streptococcus dysgalactiae, Rickettsia felis (cat-flea typhus), Sarcoptes scabiei (sarcoptic mange) and Giardia (Smout et al 2017a). We published the first report of the zoonotic hookworm Ancylostoma ceylanicum in domestic dogs and soil samples in rainforest areas of Far North Queensland (Smout et al 2017b). This presents a health risk for the aboriginal communities and tourists who utilise these areas. We also found a high prevalence of the zoonotic heartworm Dirofilaria immitis in dingoes rural Far North Queensland, which has implications for the health of residents as well as their domestic dogs and cats (Smout et al 2015).
Wildlife health surveillance, outbreak investigation and risk assessment:
Understanding the interactions between wildlife, domestic animals and humans is an important component of our research. Shima et al are investigating the health status of Lumholtz's tree-kangaroo (Dendrolagus lumholtzi) populations in the Atherton tablelands. In particular we are interested in the negative effects of living alongside humans in fragmented habitat, such as: car strikes, attacks from domestic dogs, and antibiotic resistant bacteria.
Another system we are investigating is the complex interactions between endangered snow leopards (Panthera uncia), local herders, native rodents, domestic animals and the environment. Esson et al is undertaking work in the remote Tost Mountains of the South Gobi region of Mongolia. Interviews with local herders, parasite surveys in domestic and prey species, analysis of water sources, and snow leopard movement data will be combined to form a picture of the threats to this iconic species.
Surveillance of viral diseases in wild and captive Australian reptiles is another research area of our group. Ranavirus is group of viruses is responsible for mass die-offs in many populations of fish, amphibians and reptiles around the world. Bohle iridovirus (BIV) is a highly infectious Australian ranavirus, originally discovered in the city of Townsville (Speare & Smith 1992). Wirth et al is investigating the prevalence/distribution of ranavirus in northern Queensland freshwater turtle populations and the pathogenesis of BIV in the Australian Emydura macquarii krefftii freshwater turtle. Maclaine et al is investigating adenovirus and ranavirus in captive and wild Australian lizards. This includes conducting molecular surveys of captive and wild lizards; and ranaviral susceptibility and pathogenesis trials in juvenile eastern water dragons
Banks DJD, Copeman, DB Skerratt LF. 2006. Echinococcus granulosus in northern Queensland. 2. Ecological determinants of infection in beef cattle. Australian Veterinary Journal 84: 308-311. DOI: 10.1111/j.1751-0813.2006.00021.x
Berger L, Speare R, Daszak P, Green DE, Cunningham AA, Goggin CL, Slocombe R, Ragan MA, Hyatt AD, McDonald KR, Hines HB, Lips KR, Marantelli G, Parkes H. 1998. Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. Proc Nat Acad Sci USA. 95: 9031-9036.
Berger L, Speare R, Hines HB, Marantelli G, Hyatt AD, Olsen V, McDonald KR, Clarke JM, Gillespie G, Mahony M, Skerratt LF, Sheppard N, Williams C, Tyler M. 2004. Mortality in amphibians due to chytridiomycosis increases in winter with lower experimental temperatures. Australian Veterinary Journal 82: 434-439. DOI: 10.1111/j.1751-0813.2004.tb11137.x
Brannelly LA, Berger L, Marrantelli G, Skerratt LF. 2015. Low humidity is a failed treatment option for chytridiomycosis in the critically endangered southern corroboree frog. Wildlife Research 42(1) 44-49 DOI.org/10.1071/WR14097
Garland S, James TY, Blair D, Berger L, Skerratt LF. 2011. Polymorphic repetitive loci of the amphibian pathogen Batrachochytrium dendrobatidis. Diseases of Aquatic Organisms 97:1-9. DOI: 10.3354/dao02396
Hoque MA, Burgess GW, Karo-Karo D, Cheam AL, Skerratt LF. 2012. Monitoring of wild birds for Newcastle disease virus in north Queensland, Australia. Preventive Veterinary Medicine 103:49-62. DOI: 10.1016/j.prevetmed.2011.08.013
Kosch TA, Eimes, JA, Didinger C, Brannelly, LA, Waldman B, Berger L, Skerratt LF. (2017) Characterization of MHC class IA in the endangered southern corroboree frog. Immunogenetics, 69. pp. 165-174. DOI: 10.1007/s00251-016-0965-3
Martin G, Webb RJ, Chen C, Skerratt LF. 2017. Microclimates Might Limit Indirect Spillover of the Bat Borne Zoonotic Hendra Virus. Microbial Ecology 74(1) DOI: 10.1007/s00248-017-0934-x
Martin G, Arenas CY, Roberts BJ, Chen C, Plowright RK, Webb RJ, Skerratt LF. 2016. Climatic suitability influences species specific abundance patterns of Australian flying foxes and risk of Hendra virus spillover. One Health 2:115-121 DOI: 10.1016/j.onehlt.2016.07.004
Mendez D, Judd J, Speare R. 2012. Unexpected result of Hendra virus outbreaks for veterinarians, Queensland , Australia. Emerging Infectious Diseases18(1):83-85 DOI: 10.3201/eid1801.111006
Mendez D, Büttner P, Kelly J, Nowak M, Speare R. 2017. Difficulties experienced by veterinarianswhen communicating about emerging zoonotic risks with animal owners: the case of Hendra virus. BMC Veterinary Research 13(1). DOI: 10.1186/s12917-017-0970-2
Mendez D, Büttner P, Speare R. 2014. Hendra virus in Queensland, Australia, during the winter of 2011:Veterinarians on the path to better management strategies. Preventive Veterinary Medicine 117(1) 40-51. DOI: 10.1016/j.prevetmed.2014.08.002
Mendez D, Kelly J, , Büttner P, Nowak M, Speare R. 2014. Management of the slowly emerging zoonosis, Hendra virus, by private veterinarians in Queensland, Australia: a qualitative study. BMC Veterinary Research 10(1):215. DOI: 10.1186/s12917-014-0215-6Murray KA, Rosauer D, McCallum H, Skerratt LF. 2011. Integrating species traits with extrinsic threats: closing the gap between predicting and preventing species declines. Proceedings of the Royal Society B 278:1515–1523. DOI: 10.1098/rspb.2010.1872
Phillott AD, Speare R, Hines HB, Meyer E, Skerratt LF, McDonald KR, Cashins S, Berger L, Mendez D. 2010. Hygiene principles to minimise exposure of amphibians to pathogens during field studies. Diseases of Aquatic Organisms. Special 4:8. Chytridiomycosis: an emerging disease 92: 175-185. DOI: 10.3354/dao02162.
Puschendorf R, Hoskin CJ, Cashins SD, McDonald K, Skerratt LF, Vanderwal J, Alford RA. 2011. Environmental refuge from amphibian extinction. Conservation Biology25: 956-964. DOI: 10.1111/j.1523-1739.2011.01728.x
aScheele BC, Skerratt LF, Hunter DA, Banks SC, Pierson JC, Driscoll DA, Byrne PG, Berger L.2017. Disease-associated change in an amphibian life-history trait. Oecologia. doi: 10.1007/s00442-017-3911-7
bScheele BC, Hunter DA, Brannelly LA, Skerratt LF, Driscoll DA. 2017. Reservoir-host amplification of disease impact in an endangered amphibian. Conserv Biol.31(3):592-600. doi: 10.1111/cobi.12830.
Scheele BC, Hunter DA, Banks SC, Pierson JC, Skerratt LF, Webb R, Driscoll DA. 2016. High adult mortality in disease-challenged frog populations increases vulnerability to drought. J Anim Ecol. 85(6):1453-1460. doi: 10.1111/1365-2656.12569.
Skerratt LF, Berger L, Speare R, Cashins S, McDonald K, Phillott A, Hines H, Kenyon N. 2007. The spread of chytridiomycosis has caused the rapid global decline and extinction of frogs. EcoHealth 4: 125-134. DOI: 10.1007/s10393-007-0093-5
Skerratt LF, Garner TWJ, Hyatt AD. 2009. Determining causality and controlling disease is based on collaborative research involving multidisciplinary approaches. Ecohealth 6: 331-334. DOI 10.1007/s10393-010-0292-3
Skerratt LF, Mendez D, McDonald KR, Garland S, Livingstone J, Berger L, Speare R. 2011. Validation of diagnostic tests in wildlife: the case of chytridiomycosis in wild amphibians. Journal of Herpetology 45: 444-450. DOI: 10.1670/10-193.1
Smout FA, Skerratt LF, Butler JRA, Johnson CN, Congdon BC. 2015. Dingoes (Canis dingo Meyer, 1793) continue to be an important reservoir host of Dirofilaria immitis in low density housing areas in Australia. Veterinary Parasitology 215:6-10. DOI: 10.1016/j.vetpar.2015.10.020
aSmout F, Schrieber L, Speare R, Skerratt LF. 2017. More bark than bite: Comparative studies are needed to determine the importance of canine zoonoses in Aboriginal communities. A critical review of published research. Zoonoses and public health. DOI: 10.1111/zph.12354
bSmout FA, Skerratt LF, Butler JRA, Johnson CN, Congdond BC, Thompson RCA. 2017. The hookworm Ancylostoma ceylanicum: An emerging public health risk in Australian tropical rainforests and Indigenous communities. One Health 3:66-69. DOI: 10.1016/j.onehlt.2017.04.002Speare R, Smith JR. 1992. An iridovirus-like agent isolated from the ornate burrowing frog Limnodynastes ornatus in northern Australia. Dis Aquat Org 14:51–57.Speare R, Mendez D, Judd J, Reid S, Tzipori S, Massey PD. 2015. Willingness to Consult a Veterinarian on Physician’s Advice for Zoonotic Diseases: A Formal Role for Veterinarians in Medicine? PLoS ONE 10(8)1-8. DOI: 10.1371/journal.pone.0131406
Voyles J, Young S, Berger L, Campbell C, Voyles WF, Dinudom A, Cook D, Webb R, Alford RA, Skerratt LF, Speare R. 2009. Pathogenesis of chytridiomycosis, a cause of catastrophic amphibian declines. Science 326: 582-585. DOI: 10.1126/science.1176765
Woodward A, Berger L, Skerratt LF. 2014. In vitro sensitivity of the amphibian pathogen Batrachochytrium dendrobatidis to antifungal therapeutics. Research in Veterinary Science 97, 364–366. DOI:10.1016/j.rvsc.2014.06.013
Young S, Speare R, Berger L, Skerratt L. 2012. Chloramphenicol with fluid and electrolyte therapy cures terminally ill green tree frogs (litoria caerulea) with chytridiomycosis. Journal of Zoo and Wildlife Medicine 43(2):330-337
2017 L Berger, TA Kosch, LF Skerratt. Can we stop amphibian extinction by increasing immunity to the frog chytrid fungus? Experiment. $6K
2012–2015 LF Skerratt, H McCallum, K Murray, R Plowright. Modelling the transmission of Hendra virus between flying foxes and horses. RIRDC $150K
2012–2014 LF Skerratt, L Berger, R Speare, S Cashins, P Harlow, D Hunter, LP110200240. Using Adaptive and Innate Immunity to Chytridiomycosis to Save Amphibians from Extinction. ARC Linkage $210K
2012–2014 L Berger, LF Skerratt, R Speare J Mulvenna. DP120100811 Mechanisms of virulence of chytridiomycosis. ARC Discovery $230K
2011–2016 L Berger. FT100100375 Evolution of virulence and host immunity in an emerging disease, Chytridiomycosis as a model of a multi-host pandemic., ARC Future Fellow. $704K
2011–2013 LF Skerratt, L Berger, R Speare, S Cashins, E Rosenblum. Using Gene Expression Microarrays to Investigate the Genetic Basis of Immunity to Chytridiomycosis. Morris Animal Foundation, USA $95K
2009–2010 LF Skerratt, Berger L, Speare R, Hunter D, Marantelli G, Harlow P, Cashins SD. Inducing adaptive immunity and testing for innate immunity to chytridiomycosis to improve the success of reintroduction programs of endangered frogs Australian Biosecurity Cooperative Research Centre for Emerging Infectious Disease. $230K
2007–2010 G Burgess, LF Skerratt and B Congdon. “Epidemiology of avian influenza in aquatic birds in northern Queensland”. Australian Biosecurity Cooperative Research Centre for Emerging Infectious Disease, $321K