Chytrid fungi and global amphibian declines

Abstract

Discovering that chytrid fungi cause chytridiomycosis in amphibians represented a paradigm shift in our understanding of how emerging infectious diseases contribute to global patterns of biodiversity loss. In this Review we describe how the use of multidisciplinary biological approaches has been essential to pinpointing the origins of amphibian-parasitizing chytrid fungi, including Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans, as well as to timing their emergence, tracking their cycles of expansion and identifying the core mechanisms that underpin their pathogenicity. We discuss the development of the experimental methods and bioinformatics toolkits that have provided a fuller understanding of batrachochytrid biology and informed policy and control measures.

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Fig. 1: Global distribution of Batrachochytrium.
Fig. 2: Global spread of Batrachochytrium dendrobatidis and the amphibian trade.
Fig. 3: Factors influencing the virulence of batrachochytrids.
Fig. 4: Pathogenic potential of batrachochytrids.

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Acknowledgements

We acknowledge funding from the Natural Environment Research Council (NERC) (NE/E006701/1, NE/E006841/1, NE/G002193/1, NE/K014455/1, NE/K012 509/1, NE/M000591/1, NE/N009800/1, NE/N009967/1, NE/S000844/1, NE/S000992/1), The Morris Animal Foundation (D12ZO-002 and D16ZO-022) and the Leverhulme Trust (RPG-2014-273). We thank S. O’Hanlon and P. Ghosh, who assisted with drafting the figures. M.C.F. is a Fellow in the CIFAR ‘Fungal Kingdom’ Program.

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Correspondence to Matthew C. Fisher.

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Nature Reviews Microbiology thanks T. James and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Related links

Amphibian Disease Portal: https://amphibiandisease.org

AmphibiaWeb: https://amphibiaweb.org

CITES: http://www.cites.org

EpiCollect: https://five.epicollect.net/project/bd-global-isolation-protocol

North American Bsal Task Force: http://www.salamanderfungus.org/about-bsal/

TRAFFIC: https://www.traffic.org/

Glossary

Panzootic

Global outbreak of an infectious disease in animals.

Multilocus sequence typing

Matching the DNA sequences of fragments of multiple housekeeping genes in order to assay genetic diversity.

Epizootics

Local outbreaks of an infectious disease in animals.

Bayesian-based haplotype clustering

Population assignment using large numbers of resequenced genomes.

Mutation–drift equilibrium

State of balance in which the rate at which variation is lost through genetic drift is equal to the rate at which new variation is created by mutation.

Tajima’s D statistic

Population genetic test statistic distinguishing between DNA sequences that evolve neutrally (at mutation–drift equilibria) and those that evolve in response to a nonrandom process, such as demographic change or natural selection.

Phased

Subjected to a process of assigning alleles to the paternal and maternal chromosomes.

Crossovers

Segregation of alleles between homologous chromosomes through DNA breaks and reconnections.

Meiosis

Sexual recombination resulting in crossovers.

Mating-type alleles

Genes that regulate compatibility leading to meiosis in fungi, also called mating-type ‘idiomorphs’.

Chromosomal copy number variation

State in which the number of copies of a haplotype varies between one individual and another, also known as ‘aneuploidy’.

Amphibian arks

Ex situ breeding of threatened species in biocontainment facilities.

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Fisher, M.C., Garner, T.W.J. Chytrid fungi and global amphibian declines. Nat Rev Microbiol (2020). https://doi.org/10.1038/s41579-020-0335-x

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