Voriconazole is an effective treatment for clinical chytridiomycosis in two Critically Endangered amphibians

Voriconazole treatment for amphibian chytridiomycosis has emerged as a less toxic alternative to the widely used itraconazole, although its efficacy needs to be validated across different species, particularly for frogs with clinical signs of disease. We assessed the effectiveness of topical voriconazole antifungal treatments for subclinical and clinical chytrid infections after experimental Batrachochytrium dendrobatidis (Bd) exposure. In addition, we looked to validate this treatment for use with multiple age classes of 2 highly susceptible, Critically Endangered Australian myobatrachid frogs: southern corroboree frogs Pseudophryne corroboree and northern corroboree frogs P. pengilleyi. Treatment involved twice daily topical application of a 0.00015% voriconazole solution for 7 d or until clear of Bd. Supportive care was provided for frogs displaying clinical signs of chytridiomycosis. This study was conducted across 2 experiments: experiment 1 (Expt 1) involved only P. corroboree and Expt 2 included P. corroboree and P. pengilleyi. In Expt 1, voriconazole treatment cleared Bd from 78% (N = 21/27) of infected P. corroboree, resulting in 68% survival among the P. corroboree with clinical chytridiomycosis. In Expt 2, 100% of Bd-positive P. pengilleyi (N = 7) cleared and survived infection, including all 4 cases with clinical disease. In Expt 2, none of the P. corroboree (4) tested positive for Bd, and all remained normal throughout treatment. Our results demonstrate that voriconazole is an effective treatment for chytridiomycosis in P. corroboree and P. pengilleyi, and that clinically ill frogs of multiple age classes can recover with the addition of electrolyte therapy and antibiotics.