Presence of low virulence chytrid fungi could protect European amphibians from more deadly strains

Mark Greener ,Siska Croubels,Moira Kelly,Niels De Troyer,Luc Lens,Gwij Stegen,Stefano Canessa,Elin Verbrugghe,Frank Pasmans,M Vila-Escalé ,Muriel Vervaeke,Daniel Fernández‐Giberteau ,Sarah Van Praet,Mark Blooi,Robby Van Leeuwenberg,Diederik Strubbe,Zhimin Li,Wouter Beukema,Salvador Carranza,Peter Goethals,An Martel

doi:10.1038/s41467-020-19241-7

Abstract

Wildlife diseases are contributing to the current Earth’s sixth mass extinction; one disease, chytridiomycosis, has caused mass amphibian die-offs. While global spread of a hypervirulent lineage of the fungus Batrachochytrium dendrobatidis (BdGPL) causes unprecedented loss of vertebrate diversity by decimating amphibian populations, its impact on amphibian communities is highly variable across regions. Here, we combine field data with in vitro and in vivo trials that demonstrate the presence of a markedly diverse variety of low virulence isolates of BdGPL in northern European amphibian communities. Pre-exposure to some of these low virulence isolates protects against disease following subsequent exposure to highly virulent BdGPL in midwife toads (Alytes obstetricans) and alters infection dynamics of its sister species B. salamandrivorans in newts (Triturus marmoratus), but not in salamanders (Salamandra salamandra). The key role of pathogen virulence in the complex host-pathogen-environment interaction supports efforts to limit pathogen pollution in a globalized world.

Highlights

Wildlife diseases are contributing to the current Earth’s sixth mass extinction; one disease, chytridiomycosis, has caused mass amphibian die-offs
25 cases of amphibian mortality, comprising 47 animals belonging to seven species (1 Rana temporaria, 20 Bufo bufo, 2 Triturus cristatus, 11 Ichthyosaura alpestris, 7 Lissotriton vulgaris, 3 Salamandra salamandra, 3 Lissotriton helveticus) were reported to the regional hotline and submitted for postmortem analysis during a 4-year period (2015–2018)
During the 4-year study, the midwife toad populations persisted in the presence of Batrachochytrium dendrobatidis (Bd) infections (Supplementary Table 2)

Summary

Introduction

Wildlife diseases are contributing to the current Earth’s sixth mass extinction; one disease, chytridiomycosis, has caused mass amphibian die-offs. While global spread of a hypervirulent lineage of the fungus Batrachochytrium dendrobatidis (BdGPL) causes unprecedented loss of vertebrate diversity by decimating amphibian populations, its impact on amphibian communities is highly variable across regions. Pre-exposure to some of these low virulence isolates protects against disease following subsequent exposure to highly virulent BdGPL in midwife toads (Alytes obstetricans) and alters infection dynamics of its sister species B. salamandrivorans in newts (Triturus marmoratus), but not in salamanders (Salamandra salamandra). Despite its presumed high virulence and global distribution, amphibian community declines caused by BdGPL are predominantly limited to disease hotspots in North, Central and South America, Australia, Europe and Africa[1,2,7,8,9]. We estimated the impact of pre-existing infections with less virulent BdGPL isolates on virulent BdGPL and Bsal infections

Methods

Results

Conclusion