The first detection of the fungal pathogen batrachochytrium dendrobatidis in Norway with no evidence of population declines for great crested and smooth newts based on modeling on traditional trapping data

AbstractDevelopment of infectious diseases within hosts may be shaped by environmental conditions that cause tradeoffs in energetic demands for immune responses against demands for host growth and survival. Environmental conditions may influence these tradeoffs by affecting size of hosts, or tradeoffs may change across seasons, thereby altering the impacts of diseases on hosts. In the present study, we exposed northern leopard frog (Lithobates pipiens) tadpoles to varying larval environments (low leaf litter, high density of conspecifics, 40 µg/L atrazine, caged fish, or control) that influenced size at metamorphosis, a measure of host quality. Subsequently, we exposed these metamorphs of to Batrachochytrium dendrobatidis (Bd), a fungal pathogen linked to worldwide host population declines, at metamorphosis and/or 12 weeks later, prior to overwintering. Bd exposure dramatically reduced survival during overwintering and the effect was strongest when frogs were exposed both at metamorphosis and before overwintering. Larval environments, which determined host size, did not influence effects of Bd. Stage-structured models built to assess the impacts of Bd exposure on host populations suggest that Bd exposure at metamorphosis or before overwintering would reduce annual population growth rates by an average of 19% and 41%, respectively. Our study indicates that northern leopard frog hosts suffered little effects of Bd exposures following metamorphosis and that lower host quality did not hamper a frog’s ability to respond to Bd. Instead, we provide evidence that Bd exposure can reduce survival and result in population size reductions via reduced recruitment from overwintering mortality, providing a plausible mechanism for enigmatic declines of amphibians in temperate regions.

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The Effect of Aquatic and Terrestrial Environmental Factors on the Interaction Between Grand Teton Boreal Toads and a Lethal Fungal Pathogen

The UW National Parks Service Research Station Annual Reports ◽

10.13001/uwnpsrc.2008.3723 ◽

2008 ◽

Vol 31 ◽

pp. 125-131

Author(s):

Peter Murphy ◽

Sophie St-Hilaire ◽

Charles Peterson

Keyword(s):

Fungal Pathogen ◽

Batrachochytrium Dendrobatidis ◽

Chytrid Fungus ◽

Population Declines ◽

Amphibian Skin ◽

Amphibian Species ◽

American Bullfrog ◽

The North ◽

S 100 ◽

Boreal Toads

Batrachochytrium dendrobatidis (Bd), the chytrid fungus which infects keratinized amphibian skin and causes the lethal disease chytridiomycosis, has been linked to population declines and extinctions worldwide (Lips et al. 2006). Amphibians infected with Bd may suffer a variety of outcomes. Individuals of some species have been killed by :S 100 Bd zoospores, while other species, such as the North American bullfrog Rana catesbiana, are highly resistant (Daszak et al. 2004). Within an amphibian species, populations may also respond differently to Bd, with some declining et al. remaining stable (Kriger and Hero 2006). Divergent outcomes among species and populations with respect to Bd may arise from at least three factors, or their interaction.

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Modelling the amphibian chytrid fungus spread by connectivity analysis: towards a national monitoring network in Italy

Biodiversity and Conservation ◽

10.1007/s10531-021-02224-5 ◽

2021 ◽

Author(s):

Andrea Costa ◽

Lorenzo Dondero ◽

Giorgia Allaria ◽

Bryan Nelson Morales Sanchez ◽

Giacomo Rosa ◽

...

Keyword(s):

Batrachochytrium Dendrobatidis ◽

National Level ◽

Monitoring Network ◽

Electric Circuit ◽

Population Declines ◽

Climate Data ◽

Landscape Permeability ◽

National Monitoring ◽

Climatic Scenarios ◽

Amphibian Chytrid Fungus

AbstractThe emerging amphibian disease, Batrachochytrium dendrobatidis (Bd), is driving population declines worldwide and even species extinctions in Australia, South and Central America. In order to mitigate effects of Bd on amphibian populations, high-exposed areas should be identified at the local scale and effective conservation measures should be planned at the national level. This assessment is actually lacking in the Mediterranean basin, and in particular in Italy, one of the most relevant amphibian diversity hotspots in the entire region. In this study, we reviewed the available information on Bd in Italy, and conducted a 5-year molecular screening on 1274 individual skin swabs belonging to 18 species. Overall, we found presence of Bd in 13 species and in a total of 56 known occurrence locations for peninsular Italy and Sardinia. We used these occurrence locations and climate data to model habitat suitability of Bd for current and future climatic scenarios. We then employed electric circuit theory to model landscape permeability to the diffusion of Bd, using a resistance map. With this procedure, we were able to model, for the first time, the diffusion pathways of Bd at the landscape scale, characterising the main future pathways towards areas with a high probability of Bd occurrence. Thus, we identified six national protected areas that will become pivotal for a nationally-based strategic plan in order to monitor, mitigate and possibly contrast Bd diffusion in Italy.

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Ancestral chytrid pathogen remains hypervirulent following its long coevolution with amphibian hosts

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2019.0833 ◽

2019 ◽

Vol 286 (1904) ◽

pp. 20190833 ◽

Cited By ~ 3

Author(s):

Minjie Fu ◽

Bruce Waldman

Keyword(s):

Batrachochytrium Dendrobatidis ◽

Population Declines ◽

Amphibian Species ◽

South Korean ◽

Global Pandemic ◽

Litoria Caerulea ◽

Experimental Treatments ◽

Amphibian Chytrid Fungus ◽

Genomic Recombination ◽

Blank Solution

Many amphibian species around the world, except in Asia, suffer morbidity and mortality when infected by the emerging infectious pathogen Batrachochytrium dendrobatidis (Bd). A lineage of the amphibian chytrid fungus isolated from South Korean amphibians (BdAsia-1) is evolutionarily basal to recombinant global pandemic lineages (BdGPL) associated with worldwide amphibian population declines. In Asia, the Bd pathogen and its amphibian hosts have coevolved over 100 years or more. Thus, resilience of Asian amphibian populations to infection might result from attenuated virulence of endemic Bd lineages, evolved immunity to the pathogen or both. We compared susceptibilities of an Australasian amphibian, Litoria caerulea , known to lack resistance to BdGPL, with those of three Korean species, Bufo gargarizans , Bombina orientalis and Hyla japonica , after inoculation with BdAsia-1, BdGPL or a blank solution. Subjects became infected in all experimental treatments but Korean species rapidly cleared themselves of infection, regardless of Bd lineage. They survived with no apparent secondary effects. By contrast, L. caerulea , after infection by either BdAsia-1 or BdGPL, suffered deteriorating body condition and carried progressively higher Bd loads over time. Subsequently, most subjects died. Comparing their effects on L. caerulea , BdAsia-1 induced more rapid disease progression than BdGPL. The results suggest that genomic recombination with other lineages was not necessary for the ancestral Bd lineage to evolve hypervirulence over its long period of coevolution with amphibian hosts. The pathogen's virulence may have driven strong selection for immune responses in endemic Asian amphibian host species.

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Recovery and resiliency of skin microbial communities on the southern leopard frog (Lithobates sphenocephalus) following two biotic disturbances

Animal Microbiome ◽

10.1186/s42523-020-00053-5 ◽

2020 ◽

Vol 2 (1) ◽

Author(s):

Denita M. Weeks ◽

Matthew J. Parris ◽

Shawn P. Brown

Keyword(s):

Microbial Communities ◽

Fungal Pathogen ◽

Bacterial Species ◽

Leopard Frog ◽

Multiple Time ◽

Population Declines ◽

Community Interactions ◽

Amphibian Species ◽

Functional Relationships ◽

Species Specific

Abstract Background Microorganisms have intimate functional relationships with invertebrate and vertebrate taxa, with the potential to drastically impact health outcomes. Perturbations that affect microbial communities residing on animals can lead to dysbiosis, a change in the functional relationship, often associated with disease. Batrachochytrium dendrobatidis (Bd), a fungal pathogen of amphibians, has been responsible for catastrophic amphibian population declines around the globe. Amphibians harbor a diverse cutaneous microbiome, including some members which are known to be antagonistic to Bd (anti-Bd). Anti-Bd microorganisms facilitate the ability of some frog populations to persist in the presence of Bd, where other populations that lack anti-Bd microorganisms have declined. Research suggests disease-antagonistic properties of the microbiome may be a function of microbial community interactions, rather than individual bacterial species. Conservation efforts have identified amphibian-associated bacteria that exhibit anti-fungal properties for use as ‘probiotics’ on susceptible amphibian populations. Probiotic application, usually with a single bacterial species, may benefit from a greater understanding of amphibian species-specific microbiome responses to disturbances (e.g. dysbiosis vs. recovery). We assessed microbiome responses to two microbial disturbance events over multiple time points. Results Exposing Lithobates sphenocephalus (southern leopard frog) adults to the biopesticidal bacteria Bacillus thuringiensis, followed by exposure to the fungal pathogen Bd, did not have long term impacts on the microbiome. After initial shifts, microbial communities recovered and returned to a state that resembled pre-disturbance. Conclusions Our results indicate microbial communities on L. sphenocephalus are robust and resistant to permanent shifts from some disturbances. This resiliency of microbial communities may explain why L. sphenocephalus is not experiencing the population declines from Bd that impacts many other species. Conservation efforts may benefit from studies outlining amphibian species-specific microbiome responses to disturbances (e.g. dysbiosis vs. recovery). If microbial communities on a threatened amphibian species are unlikely to recover following a disturbance, additional measures may be implemented to ameliorate the impacts of physical and chemical stressors on host-associated microbial communities.

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Body length of Hylodes cf. ornatus and Lithobates catesbeianus tadpoles, depigmentation of mouthparts, and presence of Batrachochytrium dendrobatidis are related

Brazilian Journal of Biology ◽

10.1590/s1519-69842013000100021 ◽

2013 ◽

Vol 73 (1) ◽

pp. 195-199 ◽

Cited By ~ 10

Author(s):

CA. Vieira ◽

LF. Toledo ◽

JE. Longcore ◽

JR. Longcore

Keyword(s):

North America ◽

South America ◽

Body Length ◽

Fungal Pathogen ◽

Batrachochytrium Dendrobatidis ◽

Strong Association ◽

Experimental Studies ◽

Sao Paulo ◽

Lithobates Catesbeianus ◽

Pure Cultures

A fungal pathogen Batrachochytrium dendrobatidis (Bd), which can cause morbidity and death of anurans, has affected amphibian populations on a worldwide basis. Availability of pure cultures of Bd isolates is essential for experimental studies to understand the ecology of this pathogen. We evaluated the relationships of body length of Hylodes cf. ornatus and Lithobates catesbeianus tadpoles to depigmentation of mouthparts and determined if dekeratinization indicated an infection by Batrachochytrium dendrobatidis. A strong association existed for both species, one from South America (Brazil: São Paulo) and one from North America (USA: Maine). We believe it prudent not to kill adult amphibians if avoidable, thus obtaining tissue for isolating Bd from tadpoles is reasonable because infected specimens of some species can be selectively collected based on depigmentation of mouthparts.

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Epidemic and endemic pathogen dynamics correspond to distinct host population microbiomes at a landscape scale

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.0944 ◽

2017 ◽

Vol 284 (1857) ◽

pp. 20170944 ◽

Cited By ~ 28

Author(s):

Andrea J. Jani ◽

Roland A. Knapp ◽

Cheryl J. Briggs

Keyword(s):

Infectious Disease ◽

Fungal Pathogen ◽

Batrachochytrium Dendrobatidis ◽

Infection Intensity ◽

Host Population ◽

Symbiotic Bacteria ◽

Skin Microbiome ◽

Pathogen Infection ◽

Microbiome Composition ◽

Pathogen Invasion

Infectious diseases have serious impacts on human and wildlife populations, but the effects of a disease can vary, even among individuals or populations of the same host species. Identifying the reasons for this variation is key to understanding disease dynamics and mitigating infectious disease impacts, but disentangling cause and correlation during natural outbreaks is extremely challenging. This study aims to understand associations between symbiotic bacterial communities and an infectious disease, and examines multiple host populations before or after pathogen invasion to infer likely causal links. The results show that symbiotic bacteria are linked to fundamentally different outcomes of pathogen infection: host–pathogen coexistence (endemic infection) or host population extirpation (epidemic infection). Diversity and composition of skin-associated bacteria differed between populations of the frog, Rana sierrae , that coexist with or were extirpated by the fungal pathogen, Batrachochytrium dendrobatidis (Bd). Data from multiple populations sampled before or after pathogen invasion were used to infer cause and effect in the relationship between the fungal pathogen and symbiotic bacteria. Among host populations, variation in the composition of the skin microbiome was most strongly predicted by pathogen infection severity, even in analyses where the outcome of infection did not vary. This result suggests that pathogen infection shapes variation in the skin microbiome across host populations that coexist with or are driven to extirpation by the pathogen. By contrast, microbiome richness was largely unaffected by pathogen infection intensity, but was strongly predicted by geographical region of the host population, indicating the importance of environmental or host genetic factors in shaping microbiome richness. Thus, while both richness and composition of the microbiome differed between endemic and epidemic host populations, the underlying causes are most likely different: pathogen infection appears to shape microbiome composition, while microbiome richness was less sensitive to pathogen-induced disturbance. Because higher richness was correlated with host persistence in the presence of Bd, and richness appeared relatively stable to Bd infection, microbiome richness may contribute to disease resistance, although the latter remains to be directly tested.

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Susceptibility of amphibians to chytridiomycosis is associated with MHC class II conformation

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2014.3127 ◽

2015 ◽

Vol 282 (1805) ◽

pp. 20143127 ◽

Cited By ~ 71

Author(s):

Arnaud Bataille ◽

Scott D. Cashins ◽

Laura Grogan ◽

Lee F. Skerratt ◽

David Hunter ◽

...

Keyword(s):

Mhc Class Ii ◽

Batrachochytrium Dendrobatidis ◽

Binding Pocket ◽

Class Ii ◽

Population Declines ◽

Mhc Ii ◽

Resistant Species ◽

Binding Pockets ◽

Experimental Approaches ◽

Binding Groove

The pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd) can cause precipitous population declines in its amphibian hosts. Responses of individuals to infection vary greatly with the capacity of their immune system to respond to the pathogen. We used a combination of comparative and experimental approaches to identify major histocompatibility complex class II (MHC-II) alleles encoding molecules that foster the survival of Bd-infected amphibians. We found that Bd-resistant amphibians across four continents share common amino acids in three binding pockets of the MHC-II antigen-binding groove. Moreover, strong signals of selection acting on these specific sites were evident among all species co-existing with the pathogen. In the laboratory, we experimentally inoculated Australian tree frogs with Bd to test how each binding pocket conformation influences disease resistance. Only the conformation of MHC-II pocket 9 of surviving subjects matched those of Bd-resistant species. This MHC-II conformation thus may determine amphibian resistance to Bd, although other MHC-II binding pockets also may contribute to resistance. Rescuing amphibian biodiversity will depend on our understanding of amphibian immune defence mechanisms against Bd. The identification of adaptive genetic markers for Bd resistance represents an important step forward towards that goal.

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Prevalence of Batrachochytrium dendrobatidis in a Nicaraguan, micro-endemic Neotropical salamander, Bolitoglossa mombachoensis

Amphibia-Reptilia ◽

10.1163/15685381-00003077 ◽

2017 ◽

Vol 38 (1) ◽

pp. 102-107 ◽

Cited By ~ 1

Author(s):

Tariq Stark ◽

Carlijn Laurijssens ◽

Martijn Weterings ◽

An Martel ◽

Gunther Köhler ◽

...

Keyword(s):

Batrachochytrium Dendrobatidis ◽

High Elevation ◽

Environmental Context ◽

Population Declines ◽

Biodiversity Crisis ◽

Terrestrial Vertebrates ◽

The Family ◽

Global Biodiversity ◽

Low Prevalence

Amphibians are the most threatened terrestrial vertebrates on the planet and are iconic in the global biodiversity crisis. Their global decline caused by the fungal agentBatrachochytrium dendrobatidis(Bd) is well known. Declines of Mesoamerican salamanders of the family Plethodontidae, mainly affecting high elevation species, have equally been attributed toBd. Here we report the prevalence ofBdin a population of a high elevationBolitoglossaspecies in Nicaragua, since its description in 1999 until 2011 in the absence of any obvious population declines. Our findings show a low prevalence in an environmental context where pathogen driven declines would be expected to occur.

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