Fungal Batrachochytrium dendrobatidis infections proliferate during amphibian terrestrial dormancy

The spread and impact of wildlife pathogens is often seasonal, and identifying the season(s) of highest impact can be critical to biodiversity and public health management.

We report new evidence that winter host dormancy, a period generally neglected in terms of pathogen seasonal dynamics, strongly promotes the proliferation of the globally threatening amphibian fungal pathogen, Batrachochytrium dendrobatidis ( Bd ) in an endangered high‐elevation anuran host species.

Surveillance of Bd in Yosemite toads ( Anaxyrus canorus ) during their first year of life showed that Bd prevalence and intensity increased fourfold during their first terrestrial winter dormancy. High prevalence and intensity of Bd infections following winter dormancy were observed in terrestrial first‐year juveniles across multiple sites and three consecutive years, and their Bd prevalence was much higher than that observed in aquatically breeding adults during the same time frame. The infections persisted into the active season.

We integrated these results into a framework summarizing possible mechanisms of overwinter Bd maintenance.

We recommend a reconsideration of seasons promoting Bd proliferation (i.e. increases in prevalence and/or intensity) and highlight a mechanism of interannual Bd maintenance in dormant terrestrial juveniles. The importance of host dormancy to pathogen persistence and seasonal infection spread may be far greater than previously thought.