Pathogenesis of Chytridiomycosis, a Cause of Catastrophic Amphibian Declines

TLDR

Batrachochytrium dendrobatidis is a highly virulent fungal pathogen that causes chytridiomycosis and has been linked to global amphibian declines, though its lethal mechanism remains unclear. Infected green tree frogs exhibit over 50 % inhibition of epidermal electrolyte transport, significant drops in plasma sodium and potassium, and asystolic cardiac arrest, indicating that skin dysfunction is likely the cause of mortality across amphibian species.

Abstract

The pathogen Batrachochytrium dendrobatidis (Bd), which causes the skin disease chytridiomycosis, is one of the few highly virulent fungi in vertebrates and has been implicated in worldwide amphibian declines. However, the mechanism by which Bd causes death has not been determined. We show that Bd infection is associated with pathophysiological changes that lead to mortality in green tree frogs (Litoria caerulea). In diseased individuals, electrolyte transport across the epidermis was inhibited by >50%, plasma sodium and potassium concentrations were respectively reduced by approximately 20% and approximately 50%, and asystolic cardiac arrest resulted in death. Because the skin is critical in maintaining amphibian homeostasis, disruption to cutaneous function may be the mechanism by which Bd produces morbidity and mortality across a wide range of phylogenetically distant amphibian taxa.