Emerging anthropozoonotic threat in amphibian aquaculture: First report of Trichosporon asahii-induced epidemic with cross-species virulence

Trichosporon asahii, a fungal pathogen predominantly associated with immunocompromised humans, has now been identified as a novel pathogen in amphibian aquaculture. During a 2023 outbreak on a 300,000-individual bullfrog farm in Hunan Province, China, we documented 113,000 mortalities (37.7 % mortality rate) within 60 days, marking the first large-scale epidemic of putrid skin disease in commercial amphibians. Through Koch's postulate fulfillment – isolating seven T. asahii strains from lesions and reproducing disease in laboratory-infected frogs – we confirmed its causative role. Notably, BALB/c murine models revealed systemic infections, demonstrating mammalian virulence potential. These findings redefine T. asahii as a transboundary pathogen requiring coordinated veterinary-medical interventions and provide epidemiological benchmarks for developing biosecurity protocols in intensive frog farming systems.