The Amphibian Skin Microbiome and Its Protective Role Against Chytridiomycosis

Rebollar, Eria A.; Martínez-Ugalde, Emanuel; Orta, Alberto H.

doi:10.1655/0018-0831-76.2.167

Cited by 82 publications

(82 citation statements)

References 135 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…There is also a growing body of research on amphibian skin microbiome and its impacts on disease persistence 59 , 77 – 79 . The skin microbiome forms the first line of defence by the innate immune system and the diversity of the microbial community helps clear infections before they cause pathogenesis by also producing antimicrobial peptides (AMPs) 80 , 81 .…”

Section: Research Gaps and Challenges In Studies On Chytridiomycosis In Asiamentioning

confidence: 99%

Chytridiomycosis in Asian Amphibians, a Global Resource for Batrachochytrium dendrobatidis (Bd) Research

Sreedharan

Vasudevan

2021

J Indian Inst Sci

View full text Add to dashboard Cite

Chytridiomycosis is an emerging infectious disease affecting amphibians globally and it is caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd ) . Chytridiomycosis has caused dramatic declines and even extinctions in wild amphibian populations in Europe, Australia, Central and North America. Spanning over two and a half decades, extensive research has led to discovery of epizootic and enzootic lineages of this pathogen. However, the Bd –amphibian system had garnered less attention in Asia until recently when an ancestral Bd lineage was identified in the Korean peninsula. Amphibians co-exist with the pathogen in Asia, only sub-lethal effects have been documented on hosts. Such regions are ‘coldspots’ of infection and are an important resource to understand the dynamics between the enzootic pathogen— Bd and its obligate host—amphibians. Insights into the biology of infection have provided new knowledge on the multi-faceted interaction of Bd in a hyperdiverse Asian amphibian community. We present the findings and highlight the knowledge gap that exists, and propose the ways to bridge them. We emphasize that chytridiomycosis in Asia is an important wildlife disease and it needs focussed research, as it is a dynamic front of pathogen diversity and virulence.

show abstract

Section: Research Gaps and Challenges In Studies On Chytridiomycosis In Asiamentioning

confidence: 99%

Chytridiomycosis in Asian Amphibians, a Global Resource for Batrachochytrium dendrobatidis (Bd) Research

Sreedharan

Vasudevan

2021

J Indian Inst Sci

View full text Add to dashboard Cite

show abstract

“…Given the low immunocompetence of subadults against Bd (Rollins-Smith 1998, Grogan et al 2018b), reducing Bd loads on subadults using itraconazole appears insufficient to keep loads low over the longer term and increase survival (see results of Barrett and Dusy treatments). The addition of protective probiotic bacteria to the frog skin microbiome may be a possible means to reduce susceptibility of this vulnerable life stage to chytridiomycosis and increase survival to adulthood (Harris et al 2009, Bletz et al 2013, Rebollar et al 2020. In this application, the effectiveness of probiotics will depend critically on the ability by the added bacteria to establish on frog skin and maintain sufficiently high densities over the dynamics over the short term.…”

Section: Microbiome Augmentation Of Subadult Frogsmentioning

confidence: 99%

Effectiveness of antifungal treatments during chytridiomycosis epizootics in populations of an endangered frog

Knapp

Joseph

et al. 2021

Preprint

View full text Add to dashboard Cite

The recently-emerged amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has had an unprecedented impact on global amphibian populations, and highlights the urgent need to develop effective mitigation strategies against this pathogen. We conducted field antifungal treatment experiments in populations of the endangered mountain yellow-legged frog during or immediately after Bd-caused mass die-off events. The objective of the treatments was to reduce Bd infection intensity ("load") and in doing so alter frog-Bd dynamics and increase the probability of frog population persistence despite ongoing Bd infection. Experiments included treatment of early life stages (tadpoles and subadults) with the antifungal drug itraconazole, treatment of adults with itraconazole, and augmentation of the skin microbiome of subadults with Janthinobacterium lividum, a commensal bacterium with antifungal properties. All itraconazole treatments caused immediate reductions in Bd load, and produced longer-term effects that differed between life stages. In experiments focused on early life stages, Bd load was reduced in the two months immediately following treatment and was associated with increased survival of subadults. However, Bd load and frog survival returned to pre-treatment levels in less than one year, and treatment had no effect on population persistence. In adults, treatment reduced Bd load and increased frog survival over the three-year post-treatment period, consistent with frogs having developed an effective adaptive immune response against Bd. Despite this protracted period of reduced impacts of Bd on adults, recruitment of new individuals into the adult population was limited and the population eventually declined to near-extirpation. In the microbiome augmentation experiment, bathing frogs in a J. lividum solution after Bd load reduction with itraconazole increased concentrations of this bacterium on frogs, but concentrations declined to baseline levels within one month and did not have a protective effect against Bd infection. Collectively, these results suggest that Bd mitigation efforts focused on frog populations that have recently declined due to Bd emergence are ineffective in causing long-term changes in frog-Bd dynamics and increasing population persistence, due largely to the inability of early life stages to mount an effective immune response against Bd and resulting high susceptibility. This results in repeated recruitment failure and a low probability of population persistence in the face of ongoing Bd infection.

show abstract

“…The skin surface and associated mucus, with its supply of oxygen, water and nutrients, provides an ideal medium for epibiotic microbial growth [ 88 ]. Microbiota, predominantly bacteria and fungi, have been demonstrated to form diverse and complex assemblages on amphibian skin ( Figure 1 ) [ 96 ] and are thought to play a substantial role in modulating Bd infection processes [ 95 , 97 , 98 ]. They can do this via (1) directly competing with pathogenic microbes for nutrients [ 99 ]; (2) secreting antimicrobial substances with pathogen-repellent and growth-inhibiting properties [ 100 , 101 , 102 ]; (3) functionally changing the host immune response, including potential interactions with host-produced AMPs [ 103 , 104 ]; (4) contributing opportunistically to pathogenesis ( Figure 1 E) [ 105 ].…”

Section: Constitutive Defences Are Sufficient To Prevent Infectionmentioning

confidence: 99%

Immunological Aspects of Chytridiomycosis

Grogan

Humphries

Robert

et al. 2020

JoF

View full text Add to dashboard Cite

Amphibians are currently the most threatened vertebrate class, with the disease chytridiomycosis being a major contributor to their global declines. Chytridiomycosis is a frequently fatal skin disease caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). The severity and extent of the impact of the infection caused by these pathogens across modern Amphibia are unprecedented in the history of vertebrate infectious diseases. The immune system of amphibians is thought to be largely similar to that of other jawed vertebrates, such as mammals. However, amphibian hosts are both ectothermic and water-dependent, which are characteristics favouring fungal proliferation. Although amphibians possess robust constitutive host defences, Bd/Bsal replicate within host cells once these defences have been breached. Intracellular fungal localisation may contribute to evasion of the induced innate immune response. Increasing evidence suggests that once the innate defences are surpassed, fungal virulence factors suppress the targeted adaptive immune responses whilst promoting an ineffectual inflammatory cascade, resulting in immunopathology and systemic metabolic disruption. Thus, although infections are contained within the integument, crucial homeostatic processes become compromised, leading to mortality. In this paper, we present an integrated synthesis of amphibian post-metamorphic immunological responses and the corresponding outcomes of infection with Bd, focusing on recent developments within the field and highlighting future directions.

show abstract

The Amphibian Skin Microbiome and Its Protective Role Against Chytridiomycosis

Cited by 82 publications

References 135 publications

Chytridiomycosis in Asian Amphibians, a Global Resource for Batrachochytrium dendrobatidis (Bd) Research

Chytridiomycosis in Asian Amphibians, a Global Resource for Batrachochytrium dendrobatidis (Bd) Research

Effectiveness of antifungal treatments during chytridiomycosis epizootics in populations of an endangered frog

Immunological Aspects of Chytridiomycosis

Contact Info

Product

Resources

About