Treatment trial of clinically ill corroboree frogs with chytridiomycosis with two triazole antifungals and electrolyte therapy

Abstract

Chytridiomycosis caused by the pathogen Batrachochytrium dendrobatidis is an important cause of amphibian declines globally, and is the worst pathogen on record for causing biodiversity loss. The critically endangered southern corroboree frog, Pseudophryne corroboree, is functionally extinct in the wild and is surviving in captive assurance colonies. These captive colonies must remain disease free, and there is no known treatment for corroboree frogs with terminal chytridiomycosis. In this study we tested two triazole antifungals (itraconazole and voriconazole) coupled with aggressive electrolyte therapy on moribund corroboree frogs with severe chytridiomycosis. Six moribund frogs were given 20 mL baths of 0.5 μg/mL itraconazole for 5 min/day for 5 days coupled with electrolyte injections every 8 h for 3 days followed by every 12 h for 3 days. Six other moribund frogs were given 1 mL drops of 1.25 μg/mL voriconazole daily for 7 days coupled with the aggressive electrolyte therapy. While only one animal survived this treatment regime, time until death was extended for all animals by at least 3 days and infection load decreased by an average of 89.3 %. Our results suggest there is potential for recovery of terminally ill P. corroboree, and we suggest further trials include antibiotics as well as exploring variations on the above treatment regime with other antifungals.