Experimental exposure indicates the amphibian chytrid pathogen poses low risk to <scp>N</scp>ew <scp>Z</scp>ealand's threatened endemic frogs

Ohmer, Michel E. B.; Herbert, Sarah; Speare, Rick; Bishop, Phillip J.

doi:10.1111/acv.12010

Cited by 19 publications

(22 citation statements)

References 50 publications

(67 reference statements)

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“…Nonetheless, the relatively strong signal observed was not completely surprising. Several experimental studies have described substantial variation across species on their susceptibility to Bd infection and development of lethal chytridiomycosis (Blaustein et al ., ; Woodhams et al ., ; Vazquez et al ., ; Searle et al ., ; Ohmer et al ., ). It is also known that Bd susceptibility and its potential population consequences might be mediated by amphibian behavior and life history (Berger et al ., and references therein).…”

Section: Discussionmentioning

confidence: 97%

Effects of amphibian phylogeny, climate and human impact on the occurrence of the amphibian‐killing chytrid fungus

Bacigalupe

Soto‐Azat

García‐Vera

et al. 2017

Global Change Biology

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Chytridiomycosis, due to the fungus Batrachochytrium dendrobatidis (Bd), has been associated with the alarming decline and extinction crisis of amphibians worldwide. Because conservation programs are implemented locally, it is essential to understand how the complex interactions among host species, climate and human activities contribute to Bd occurrence at regional scales. Using weighted phylogenetic regressions and model selection, we investigated geographic patterns of Bd occurrence along a latitudinal gradient of 1500 km within a biodiversity hot spot in Chile (1845 individuals sampled from 253 sites and representing 24 species), and its association with climatic, socio-demographic and economic variables. Analyses show that Bd prevalence decreases with latitude although it has increased by almost 10% between 2008 and 2013, possibly reflecting an ongoing spread of Bd following the introduction of Xenopus laevis. Occurrence of Bd was higher in regions with high gross domestic product (particularly near developed centers) and with a high variability in rainfall regimes, whereas models including other bioclimatic or geographic variables, including temperature, exhibited substantially lower fit and virtually no support based on Akaike weights. In addition, Bd prevalence exhibited a strong phylogenetic signal, with five species having high numbers of infected individuals and higher prevalence than the average of 13.3% across all species. Taken together, our results highlight that Bd in Chile might still be spreading south, facilitated by a subset of species that seem to play an important epidemiological role maintaining this pathogen in the communities, in combination with climatic and human factors affecting the availability and quality of amphibian breeding sites. This information may be employed to design conservation strategies and mitigate the impacts of Bd in the biodiversity hot spot of southern Chile, and similar studies may prove useful to disentangle the role of different factors contributing to the emergence and spread of this catastrophic disease.

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Section: Discussionmentioning

confidence: 97%

Effects of amphibian phylogeny, climate and human impact on the occurrence of the amphibian‐killing chytrid fungus

Bacigalupe

Soto‐Azat

García‐Vera

et al. 2017

Global Change Biology

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“…; Ohmer et al . ). Control frogs were treated in the same manner but exposed to aged tap water containing no zoospores.…”

Section: Methodsmentioning

confidence: 97%

“…Frogs were randomly assigned to Exposed (n = 11) and Control (n = 10) groups. Exposed frogs were exposed to a dose of 250 000 Bd zoospores in 40 mL aged tap water within 300 mL plastic containers (12Á5 9 8Á3 9 5 cm) for 5 h (Berger et al 2005b;Ohmer et al 2013). Control frogs were treated in the same manner but exposed to aged tap water containing no zoospores.…”

Section: N O C U L U M P R E P a R A T I O N A N D E X P E R I M E mentioning

confidence: 99%

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Skin sloughing rate increases with chytrid fungus infection load in a susceptible amphibian

et al. 2014

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Summary1. Amphibian chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is responsible for the greatest disease-driven loss of vertebrate biodiversity in recorded history. Understanding drivers of host susceptibility to this cutaneous disease is hindered by gaps in our knowledge of the host-pathogen relationship. One such overlooked aspect of susceptibility is variation in skin maintenance processes, particularly skin turnover via routine sloughing. It has been suggested that sloughing plays a role in immune defence, by removing skin-associated microbes. Thus, skin sloughing may play an important role in the pathogenesis of chytridiomycosis. 2. To determine the relationship between skin sloughing and disease progression, we exposed adult Australian green tree frogs (Litoria caerulea) to a local Bd strain and monitored sloughing rates and individual infection loads on a naturalistic cycling temperature regime (15-23°C). 3. We determined sloughing rates in real-time by using an array of infrared video cameras to film frog behaviour and monitored infection load before and after sloughing by swabbing and analysis with quantitative PCR. 4. We found that sloughing rate increased with Bd infection load in infected frogs, but sloughing itself did not affect Bd load on the ventral skin surface. Furthermore, Bd infection did not affect the duration of characteristic sloughing behaviour, and sloughing retained rhythmicity even at high infection loads. 5. Although an increased sloughing rate might be considered advantageous for Bd-infected animals, it does not appear to curb the progression of disease and may actually contribute to the loss of physiological homoeostasis seen in terminally ill frogs by further inhibiting water and electrolyte transport across the skin. 6. By measuring sloughing rates directly for the first time, our results shed light on how Bd interacts with the physiological processes of the skin and indicate that variation in skin sloughing frequency may play a role in the observed inter-and intraspecific variation in susceptibility to disease.

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“…For example, in the case of New Zealand frogs, when L. archeyi and L. pakeka were experimentally infected with Bd they rapidly self-cured and did not show clinical signs (Shaw et al 2010;Ohmer et al 2013). Similar experiments in L. hochstetteri have shown equivocal results and indicate they are likely resistant to infection .…”

Section: Introductionmentioning

confidence: 99%

BASELINE CUTANEOUS BACTERIA OF FREE-LIVING NEW ZEALAND NATIVE FROGS (LEIOPELMA ARCHEYIANDLEIOPELMA HOCHSTETTERI) AND IMPLICATIONS FOR THEIR ROLE IN DEFENSE AGAINST THE AMPHIBIAN CHYTRID (BATRACHOCHYTRIUM DENDROBATIDIS)

Shaw

Berger

Bell

et al. 2014

Journal of Wildlife Diseases

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ABSTRACT:Knowledge of baseline cutaneous bacterial microbiota may be useful in interpreting diagnostic cultures from captive sick frogs and as part of quarantine or pretranslocation disease screening. Bacteria may also be an important part of innate immunity against chytridiomycosis, a fungal skin disease caused by Batrachochytrium dendrobatidis (Bd). In February 2009, 92 distinct bacterial isolates from the ventral skin of 64 apparently healthy Leiopelma archeyi and Leiopelma hochstetteri native frogs from the Coromandel and Whareorino regions in New Zealand were identified using molecular techniques. The most-common isolates identified in L. archeyi were Pseudomonas spp. and the most common in L. hochstetteri were Flavobacterium spp. To investigate the possible role of bacteria in innate immunity, a New Zealand strain of Bd (Kaikorai Valley-Lewingii-2008-SDS1) was isolated and used in an in vitro challenge assay to test for inhibition by bacteria. One bacterial isolate, a Flavobacterium sp., inhibited growth of Bd. These results imply that diverse cutaneous bacteria are present and may play a role in the innate defense in Leiopelma against pathogens, including Bd, and are a starting point for further investigation.

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Experimental exposure indicates the amphibian chytrid pathogen poses low risk to New Zealand's threatened endemic frogs

Cited by 19 publications

References 50 publications

Effects of amphibian phylogeny, climate and human impact on the occurrence of the amphibian‐killing chytrid fungus

Effects of amphibian phylogeny, climate and human impact on the occurrence of the amphibian‐killing chytrid fungus

Skin sloughing rate increases with chytrid fungus infection load in a susceptible amphibian

BASELINE CUTANEOUS BACTERIA OF FREE-LIVING NEW ZEALAND NATIVE FROGS (LEIOPELMA ARCHEYIANDLEIOPELMA HOCHSTETTERI) AND IMPLICATIONS FOR THEIR ROLE IN DEFENSE AGAINST THE AMPHIBIAN CHYTRID (BATRACHOCHYTRIUM DENDROBATIDIS)

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