Host identity matters in the amphibian-Batrachochytrium dendrobatidis system: fine-scale patterns of variation in responses to a multi-host pathogen

PLoS One. 2013;8(1):e54490. doi: 10.1371/journal.pone.0054490. Epub 2013 Jan 24.

Abstract

Species composition within ecological assemblages can drive disease dynamics including pathogen invasion, spread, and persistence. In multi-host pathogen systems, interspecific variation in responses to infection creates important context dependency when predicting the outcome of disease. Here, we examine the responses of three sympatric host species to a single fungal pathogen, Batrachochytrium dendrobatidis, which is associated with worldwide amphibian population declines and extinctions. Using an experimental approach, we show that amphibian species from three different genera display significant differences in patterns of pathgen-induced mortality as well as the magnitude and temporal dynamics of infection load. We exposed amphibians to one of four inoculation dose treatments at both larval and post- metamorphic stages and quantified infection load on day 8 and day 15 post-inoculation. Of the three species examined, only one (the Pacific treefrog; Pseudacris regilla) displayed "dose-dependent" responses; survival was reduced and infection load was elevated as inoculation dose was increased. We observed a reduction in survival but no differences in infection load across pathogen treatments in Cascades frogs (Rana cascadae). Western toads (Anaxyrus boreas) displayed differences in infection load but no differences in survival across pathogen treatments. Within species, responses to the pathogen varied with life history stage, and the most heavily infected species at the larval stage was different from the most heavily infected species at the post-metamorphic stage. Temporal changes in infection load were species and life history stage-specific. We show that variation in susceptibility to this multi-host pathogen is complex when viewed at a fine-scale and may be mediated through intrinsic host traits.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amphibians / growth & development
  • Amphibians / microbiology*
  • Animals
  • Chytridiomycota / pathogenicity*
  • Colony Count, Microbial
  • Host-Pathogen Interactions*
  • Larva / microbiology
  • Life Cycle Stages
  • Symbiosis

Grant support

Funding for this study was provided by the United States Forest Service (Pacific Northwest Research Station; http://www.fs.fed.us/pnw/) and the Robert and Clarice MacVicar Animal Health Scholar Award (issued through Oregon State University to SG). The funders had no role in study design, data collection and analysis, decision to publish, or presentation of the manuscript.