ORCID Profile
0000-0002-2539-2755
Current Organisations
James Cook University
,
University of Melbourne
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Publisher: Inter-Research Science Center
Date: 14-09-2007
DOI: 10.3354/DAO01838
Abstract: Mounting evidence implicates the disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis, in global hibian declines and extinctions. While the virulence of this disease has been clearly demonstrated, there is, as yet, no mechanistic explanation for how B. dendrobatidis kills hibians. To investigate the pathology of chytridiomycosis, blood s les were collected from uninfected, aclinically infected and clinically diseased hibians and analyzed for a wide range of biochemical and hematological parameters. Here, we show that green tree frogs Litoria caerulea with severe chytridiomycosis had reduced plasma osmolality, sodium, potassium, magnesium and chloride concentrations. Stable plasma albumin, hematocrit and urea levels indicated that hydration status was unaffected, signifying depletion of electrolytes from circulation rather than dilution due to increased water uptake. We suggest that B. dendrobatidis kills hibians by disrupting normal epidermal functioning, leading to osmotic imbalance through loss of electrolytes. Determining how B. dendrobatidis kills hibians is fundamental to understanding the host-pathogen relationship and thus the population declines attributed to B. dendrobatidis. Understanding the mechanisms of mortality may also explain interspecific variation in susceptibility to chytridiomycosis.
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.DCI.2017.08.018
Abstract: Temperature variability, and in particular temperature decreases, can increase susceptibility of hibians to infections by the fungus Batrachochytrium dendrobatidis (Bd). However, the effects of temperature shifts on the immune systems of Bd-infected hibians are unresolved. We acclimated frogs to 16 °C and 26 °C (baseline), simultaneously transferred them to an intermediate temperature (21 °C) and inoculated them with Bd (treatment), and tracked their infection levels and white blood cell profiles over six weeks. Average weekly infection loads were consistently higher in 26°C-history frogs, a group that experienced a 5 °C temperature decrease, than in 16°C-history frogs, a group that experienced a 5 °C temperature increase, but this pattern only approached statistical significance. The 16°C-acclimated frogs had high neutrophil:lymphocyte (N:L) ratios (suggestive of a hematopoietic stress response) at baseline, which were conserved post-treatment. In contrast, the 26°C-acclimated frogs had low N:L ratios at baseline which reversed to high N:L ratios post-treatment (suggestive of immune system activation). Our results suggest that infections were less physiologically taxing for the 16°C-history frogs than the 26°C-history frogs because they had already adjusted immune parameters in response to challenging conditions (cold). Our findings provide a possible mechanistic explanation for observations that hibians are more susceptible to Bd infection following temperature decreases compared to increases and underscore the consensus that increased temperature variability associated with climate change may increase the impact of infectious diseases.
Publisher: Springer Science and Business Media LLC
Date: 14-01-2017
Publisher: American Association for the Advancement of Science (AAAS)
Date: 11-05-2018
Abstract: Species in the fungal genus Batrachochytrium are responsible for severe declines in the populations of hibians globally. The sources of these pathogens have been uncertain. O'Hanlon et al. used genomics on a panel of more than 200 isolates to trace the source of the frog pathogen B. dendrobatidis to a hyper erse hotspot in the Korean peninsula (see the Perspective by Lips). Over the past century, the trade in hibian species has accelerated, and now all lineages of B. dendrobatidis occur in traded hibians the fungus has become ubiquitous and is ersifying rapidly. Science , this issue p. 621 see also p. 604
Publisher: Public Library of Science (PLoS)
Date: 11-09-2014
Publisher: Hindawi Limited
Date: 13-08-2019
DOI: 10.1111/CMI.13089
Abstract: Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a skin disease responsible for the global decline of hibians. Frog species and populations can vary in susceptibility, but this phenomenon remains poorly understood. Here, we investigated serotonin in the skin of infected and uninfected frogs. In more susceptible frog populations, skin serotonin rose with increasing infection intensity, but decreased in later stages of the disease. The more resistant population maintained a basal level of skin serotonin. Serotonin inhibited both Bd sporangial growth and Jurkat lymphocyte proliferation in vitro. However, serotonin accumulates in skin granular glands, and this compartmentalisation may prevent inhibition of Bd growth in vivo. We suggest that skin serotonin increases in susceptible frogs due to pathogen excretion of precursor tryptophan, but that resistant frogs are able to control the levels of serotonin. Overall, the immunosuppressive effects of serotonin may contribute to the susceptibility of frogs to chytridiomycosis.
Publisher: Wiley
Date: 14-08-2017
Publisher: Inter-Research Science Center
Date: 20-11-2008
DOI: 10.3354/DAO01975
Abstract: Hygiene protocols for handling hibians in the field and in laboratories have been proposed to decrease the transmission of chytridiomycosis caused by infection with the hibian chytrid fungus Batrachochytrium dendrobatidis, which is responsible for global hibian declines. However, these protocols are mainly based on theoretical principles. The aim of this study was to develop an evidence-based approach to hibian handling hygiene protocols by testing the survival of B. dendrobatidis on human hands and various gloves. Bare or gloved human fingers were exposed to cultured zoospores and zoosporangia of B. dendrobatidis. Survival of B. dendrobatidis on hands and gloves was tested for up to 10 min post-exposure by inoculation onto tryptone/gelatin hydrolysate/lactose (TGhL) agar plates. The effects of repeated hand washings with water and with 70% ethanol and of washing gloves with water were also tested. Bare human skin demonstrated a fungicidal effect on B. dendrobatidis by 2 min and killed 100% of cells by 6 min, but this killing effect was reduced by repeated washing with water and ethanol. Nitrile gloves killed all B. dendrobatidis on contact, but washing in water decreased this effect. Latex and polyethylene gloves had no killing effect, and B. dendrobatidis survived for over 6 min. The killing effect of vinyl gloves varied with brands and batches. These results support the use of an unused pair of gloves for each new hibian handled in either the field or the laboratory, and if this is not possible, bare hands are a preferable, although imperfect, alternative to continual use of the same pair of gloves.
Publisher: Elsevier BV
Date: 2021
DOI: 10.1016/J.FUNBIO.2021.10.004
Abstract: Mycoviruses may influence the pathogenicity of disease-causing fungi. Although mycoviruses have been found in some chytrid fungi, limited testing has not detected them in Batrachochytrium dendrobatidis (Bd), the cause of the devastating hibian disease, chytridiomycosis. Here we conducted a survey for mycovirus presence in 38 Bd isolates from Australia (n = 31), Brazil (n = 5) and South Korea (n = 2) with a combination of modern high-throughput sequencing and conventional dsRNA cellulose chromatography. Mycoviruses were not detected in any isolates. This result was unexpected, given the long evolutionary history of Bd, as well as the high prevalence of mycoviruses in related fungal species. Given our widespread s ling in Australia and the limited number of Bd introductions, we suggest that mycoviruses are uncommon or absent from Australian Bd. Testing more isolates from regions where Bd originated, as well as regions with high ersity or low fungal virulence may identify mycoviruses that could aid in disease control.
Publisher: Inter-Research Science Center
Date: 08-02-2007
DOI: 10.3354/DAO074013
Abstract: Chytridiomycosis, a disease contributing to hibian declines worldwide, is caused by the fungus Batrachochytrium dendrobatidis. Identifying efficient and practical disinfectants effective against B. dendrobatidis is important to reduce the spread of the disease both in the wild and captivity. Previous studies identified a range of suitable disinfectant strategies. We evaluated the suitability of 3 additional disinfectants: two of these (TriGene Virucidal Disinfectant Cleaner and F10 Super Concentrate Disinfectant) are mixtures of chemicals and one (Betadine Antiseptic Liquid) contains a single active ingredient, povidone iodine. The disinfectants were tested using a range of concentrations for 1,5 and 10 min to determine their ability to kill B. dendrobatidis in vitro. The measure of effectiveness was 100% kill of zoosporangia grown in multiwell plates. All disinfectants had a 100% efficacy at concentrations recommended by the manufacturers. The lowest concentrations capable of 100% kill after exposure for 1 min were 0.1 ml l(-1) for TriGene, 0.33 ml l(-1) for F10 and 100 ml l(-1) for Betadine. TriGene is the most effective disinfectant yet to be found, and both TriGene and F10 are more effective than various disinfectants tested in previous studies. TriGene and F10 are considered suitable for use in the field, as only small amounts of concentrate are needed.
Publisher: Wiley
Date: 20-12-2018
DOI: 10.1111/AEC.12695
Publisher: Wiley
Date: 03-06-2019
DOI: 10.1002/FEE.2057
Publisher: Oxford University Press (OUP)
Date: 16-03-2018
DOI: 10.1093/MMY/MYY010
Abstract: Captive and wild hibians are under threat of extinction from the deadly fungal pathogen Batrachochytrium dendrobatidis (Bd). The antifungal drug terbinafine (TBF) is used by pet owners to treat Bd-infected frogs however, it is not widely used in academic or zoological institutions due to limited veterinary clinical trials. To assess TBF's efficacy, we undertook treatment trials and pharmacokinetic studies to investigate drug absorption and persistence in frog skin and then we correlated these data to the minimal lethal concentrations (MLC) against Bd. Despite an initial reduction in zoospore load, the recommended treatment (five daily 5 min 0.01% TBF baths) was unable to cure experimentally infected alpine tree frogs and naturally infected common eastern froglets. In vitro and in vivo pharmacokinetics showed that absorbed TBF accumulates in frog skin with increased exposure, indicating its suitability for treating cutaneous pathogens via direct application. The MLC of TBF for zoosporangia was 100 μg/ml for 2 h, while the minimal inhibitory concentration was 2 μg/ml, suggesting that the drug concentration absorbed during 5 min treatments is not sufficient to cure high Bd burdens. With longer treatments of five daily 30 min baths, Bd clearance improved from 12.5% to 50%. A higher dose of 0.02% TBF resulted in 78% of animals cured however, clearance was not achieved in all in iduals due to low TBF skin persistence, as the half-life was less than 2 h. Therefore, the current TBF regime is not recommended as a universal treatment against Bd until protocols are optimized, such as with increased exposure frequency.
Publisher: Wiley
Date: 13-11-2017
DOI: 10.1111/ACV.12380
Publisher: The Royal Society
Date: 06-2016
DOI: 10.1098/RSOB.150251
Abstract: Mounting an immune response to fight disease is costly for an organism and can reduce investment in another life-history trait, such as reproduction. The terminal investment hypothesis predicts that an organism will increase reproductive effort when threatened by disease. The reproductive fitness of hibians infected with the deadly fungal pathogen Batrachochytrium dendrobatidis ( Bd ) is largely unknown. In this study, we explored gametogenesis in two endangered and susceptible frog species, Pseudophryne corroboree and Litoria verreauxii alpina. Gametogenesis, both oogenesis and spermatogenesis, increased when animals were experimentally infected with Bd . In P. corroboree , infected males have thicker germinal epithelium, and a larger proportion of spermatocytes. In L. v. alpina , infected males had more spermatic cell bundles in total, and a larger proportion of spermatozoa bundles. In female L. v. alpina , ovaries and oviducts were larger in infected animals, and there were more cells present within the ovaries. Terminal investment has consequences for the evolution of disease resistance in declining species. If infected animals are increasing reproductive efforts and producing more offspring before succumbing to disease, it is possible that population-level selection for disease resistance will be minimized.
Publisher: Inter-Research Science Center
Date: 07-09-2009
DOI: 10.3354/DAO02098
Abstract: Chytridiomycosis, a disease that has caused hibian population declines globally and elevated many species of anurans to endangered or threatened status, has recently been declared an internationally notifiable disease. Batrachochytrium dendrobatidis (Bd), the hibian chytrid fungus causing this disease, has not been previously reported in Korea or on mainland Asia. Thirty-six frog specimens representing 7 species were collected from the wild in South Korea and examined for Bd using standard PCR. Bd was detected in 14 (38.8%) s les from 3 species (Bufo gargarizans, Hyla japonica, and Rana catesbiana). Skin sections from all 14 PCR-positive frogs were examined using 2 staining techniques: haematoxylin and eosin (H&E) and Bd immunoperoxidase (IPX). In histological sections, zoosporangia were found in 6 frogs, with lower sensitivity for H&E (21%) than for IPX (46%). Intensity of infection, based on histopathology, was low in all frogs. These results confirm that Bd is present in South Korea and, hence, on the Asian mainland. Studies are urgently required to determine the impact of chytridiomycosis on Korean hibians, and to map the distribution of Bd in Korea and other Asian mainland countries.
Publisher: Springer Science and Business Media LLC
Date: 07-02-2007
Publisher: Springer Science and Business Media LLC
Date: 19-03-2018
Publisher: Wiley
Date: 24-08-2021
DOI: 10.1111/EVO.14327
Abstract: The devastating infectious disease chytridiomycosis has caused declines of hibians across the globe, yet some populations are persisting and even recovering. One understudied effect of wildlife disease is changes in reproductive effort. Here, we aimed to understand if the disease has plastic effects on reproduction and if reproductive effort could evolve with disease endemism. We compared the effects of experimental pathogen exposure (trait plasticity) and population-level disease history (evolution in trait baseline) on reproductive effort using gametogenesis as a proxy in the declining and endangered frog Litoria verreauxii alpina. We found that unexposed males from disease-endemic populations had higher reproductive effort, which is consistent with an evolutionary response to chytridiomycosis. We also found evidence of trait plasticity, where males and females were affected differently by infection: pathogen exposed males had higher reproductive effort (larger testes), whereas females had reduced reproductive effort (smaller and fewer developed eggs) regardless of the population of origin. Infectious diseases can cause plastic changes in the reproductive effort at an in idual level, and population-level disease exposure can result in changes to baseline reproductive effort therefore, in idual- and population-level effects of disease should be considered when designing management and conservation programs for threatened and declining species.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/ZO18041
Abstract: Amphibian chytridiomycosis disease has caused widespread declines and extinctions of frogs in cool, wet habitats in eastern Australia. Screening suggests that the disease does not yet occupy all areas modelled to be environmentally suitable, including rainforests on Cape York Peninsula. Cape Melville is an area of rainforest with several endemic frogs, including the stream-associated Melville Range treefrog (Litoria andiirrmalin), which is deemed at particular risk of disease impacts. We tested 40 L. andiirrmalin for chytrid infection by PCR and found them all to be negative. In conjunction with previous testing at another high-risk location, McIlwraith Range, this suggests that endemic rainforest frogs on Cape York have been spared the introduction of chytridiomycosis. We discuss how the disease could get to these areas, what can be done to reduce the risk, and suggest an emergency procedure should it be introduced.
Publisher: Oxford University Press (OUP)
Date: 14-07-2016
Abstract: One of the major causes of hibian population decline is the deadly fungal pathogen Batrachochytrium dendrobatidis, Bd Research on pathogenesis and host immunity aims to inform development of targeted conservation interventions. Studies examining global host immune responses as well as effects on lymphocytes in vitro suggest that Bd infection causes immunosuppression. However, it is unknown which hematopoietic tissues are affected and if these effects differ among host species. We investigated the effect of experimental Bd infection on three erse hibian species by quantifying the amount of hematopoietic tissue in the spleen, bone marrow and kidney. Upon Bd infection, hematopoietic tissue in the kidney tended to be depleted, while the spleen appeared unaffected. The bone marrow in highly susceptible species was depleted, whereas an increase in hematopoietic tissue was observed in the more resistant species. Our study demonstrates that species and hematopoietic tissues behave differently in response to Bd infection, and may be related to the species' susceptibility to infection.
Publisher: Springer Science and Business Media LLC
Date: 17-05-2018
DOI: 10.1038/S41598-018-24472-2
Abstract: Parasitic chytrid fungi have emerged as a significant threat to hibian species worldwide, necessitating the development of techniques to isolate these pathogens into culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing hibians. We modified a pre-existing protocol for isolating chytrids from infected animals to use toe clips and biopsies from toe webbing rather than euthanizing hosts, and distributed the protocol to researchers as part of the Bio ERsA project RACE here called the RML protocol. In tandem, we developed a lethal procedure for isolating chytrids from tadpole mouthparts. Reviewing a database of use a decade after their inception, we find that these methods have been applied across 5 continents, 23 countries and in 62 hibian species. Isolation of chytrids by the non-lethal RML protocol occured in 18% of attempts with 207 fungal isolates and three species of chytrid being recovered. Isolation of chytrids from tadpoles occured in 43% of attempts with 334 fungal isolates of one species ( Batrachochytrium dendrobatidis ) being recovered. Together, these methods have resulted in a significant reduction and refinement of our use of threatened hibian species and have improved our ability to work with this group of emerging pathogens.
Publisher: Inter-Research Science Center
Date: 13-06-2012
DOI: 10.3354/DAO02461
Abstract: Chytridiomycosis in hibians, and mucormycosis in the platypus Ornithorhynchus anatinus and hibians, are serious fungal diseases affecting these aquatic taxa. In Tasmania, Australia, the fungi that cause these diseases overlap in range along with Phytophthora cinnamomi (Pc), an invasive fungal plant pathogen. To identify disinfectants that may be useful to reduce anthropogenic spread of these fungi to uninfected wilderness areas, for ex le by bush walkers and forestry or fire-fighting operations, we tested 3 disinfectants and a fire-fighting foam against Mucor hibiorum (Ma) and tested 1 disinfectant and the foam against Batrachochytrium dendrobatidis (Bd). Combining the present study with previous work we found Bd was more susceptible to all 4 chemicals than Ma. Phytoclean, a disinfectant used at 2 to 10% for 30 s to control Pc, killed cultures of Bd at 0.075% and Ma at 5%, when also applied for 30 s. The disinfectant F10sc was not effective against Ma at standard exposures, but previous work shows Bd is killed at 0.03% with a 1 min exposure. Path-X is effective against Bd at 0.001% with a 30 s exposure and killed Ma at 1% with a 5 min exposure. Forexpan S, a foam added to water at 0.1 to 1% to control forest fires, killed Bd but not Ma when used at 1% for 2 min. Therefore, Phytoclean and Path-X have broader efficacy, although Path-X has not been trialled against Pc. Interestingly a positive mating strain of Ma (from a platypus) was more resistant to disinfectants than a negative strain (from a frog). Current protocols against Pc that involve high concentrations (10%) of Phytoclean are likely to reduce spread of pathogenic wildlife fungi, which is important for protecting bio ersity.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-10-2009
Abstract: The global hibian decline has been attributed, among other causes, to an hibian skin disease chytridiomycosis caused by the fungus Batrachochytrium dendrobatidis . However, how this pathogen causes mortality has been unclear. Voyles et al. (p. 582 ) show that this superficial skin infection may lead to cardiac failure owing to changes caused by lowered ion transport through the skin and consequent electrolyte reduction in the blood.
Publisher: Inter-Research Science Center
Date: 2005
DOI: 10.3354/DAO068089
Abstract: MS-222 (tricaine methane sulfonate) is an agent commonly used to anaesthetise or euthanize hibians used in experiments. It is administered by immersing the animal to allow absorption through the skin. Chytridiomycosis is an important disease of hibians and research involves experiments with live animals. Batrachochytrium dendrobatidis, the fungus which causes chytridiomycosis, is located in the skin and therefore the organism should come into contact with MS-222 when it is used. B. dendrobatidis is a sensitive organism which could possibly be killed by MS-222. Hence, results of chytridiomycosis studies in which MS-222 is used could be unreliable. A concentration of 2 g l(-1) and an exposure duration of 1 h is at the high end of the range at which MS-222 would be most commonly used. Exposure to 2 g l(-1) MS-222 for 1 h does not kill B. dendrobatidis cultures, suggesting that MS-222 is safe to use in chytridiomycosis studies.
Publisher: Hindawi Limited
Date: 30-04-2023
DOI: 10.1155/2023/9980566
Abstract: Chytridiomycosis is an infectious disease in hibians caused by two chytrid fungi, Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal), and is the worst infectious disease known in wildlife so far. Worldwide spread of the disease has caused unprecedented loss of global hibian ersity. Although some lineages of Bd are enzootic and are not as deadly as the pandemic lineage, nearly 40% of hibian species are still declining globally due to chytridiomycosis. Efficient surveillance and monitoring of chytridiomycosis are the immediate safeguard against rapid declines or extinctions of hibian populations. Previous studies showed that existing diagnostic assays were not sensitive to certain Bd haplotypes like those from Korea, China, India, Japan, and Brazil and thereby, there is a need for a universal, sensitive, specific, reproducible, and affordable diagnostic assay. We designed a one-step SYBR green-based quantitative polymerase chain reaction (nSYBR qPCR) for robust detection of Bd. It lifies an 82 base-pair segment between the 5.8S rRNA and ITS2 of the Bd genome. The primer pair was tested in-silico on 40 isolates from four known Bd lineages. Using skin swab s les of wild hibians and cultured zoospores from Australia and Panama, we compared the clinical specificity and sensitivity of the newly described primers to the existing TaqMan-based qPCR assay. From India, we used s les which had been previously tested with Nested PCR to validate the new primer pairs. The newly described primer pair was then tested on swab s les from Anura, Caudata and Gymnophiona from India. We report widespread chytridiomycosis with varying infection loads on them. The new assay showed comparable efficiency to the TaqMan-based qPCR assay. This diagnostic assay can facilitate widespread surveillance of chytridiomycosis where it has been previously absent, which may reveal several reservoirs of the pathogen and can improve our understanding of this important wildlife disease.
No related grants have been discovered for Rebecca Webb.