DAO 57:255-260 (2003)  -  doi:10.3354/dao057255

Fungicidal effects of chemical disinfectants, UV light, desiccation and heat on the amphibian chytrid Batrachochytrium dendrobatidis

Megan L. Johnson1, Lee Berger1,2, Lara Philips1,3, Richard Speare1,*

1School of Public Health and Tropical Medicine, James Cook University, Townsville, Queensland 4810, Australia
2Australian Animal Health Laboratory, Commonwealth Scientific and Industrial Research Organisation, Ryrie Street, Geelong, Victoria 3220, Australia
3St Patrick¹s School, The Esplanade, North Ward, Townsville, Queensland 4811, Australia

ABSTRACT: The efficacy of a number of disinfection treatments was tested on in vitro cultures of the fungus Batrachochytrium dendrobatidis, the causative agent of chytridiomycosis in amphibians. The aim was to evaluate the fungicidal effects of chemical disinfectants, sterilising ultraviolet (UV) light, heat and desiccation, using methods that were feasible for either disinfection in the field, in amphibian husbandry or in the laboratory. The chemical disinfectants tested were: sodium chloride, household bleach (active ingredient: sodium hypochlorite), potassium permanganate, formaldehyde solution, Path-XTM agricultural disinfectant (active ingredient: didecyl dimethyl ammonium chloride, DDAC), quaternary ammonium compound 128 (DDAC), Dithane, Virkon, ethanol and benzalkonium chloride. In 2 series of experiments using separate isolates of B. dendrobatidis, the fungicidal effect was evaluated for various time periods and at a range of chemical concentrations. The end point measured was death of 100% of zoospores and zoosporangia. Nearly all chemical disinfectants resulted in 100% mortality for at least one of the concentrations tested. However, concentration and time of exposure was critical for most chemicals. Exposure to 70% ethanol, 1 mg Virkon ml-1 or 1 mg benzalkonium chloride ml-1 resulted in death of all zoosporangia after 20 s. The most effective products for field use were Path-XTM and the quaternary ammonium compound 128, which can be used at dilutions containing low levels (e.g. 0.012 or 0.008%, respectively) of the active compound didecyl dimethyl ammonium chloride. Bleach, containing the active ingredient sodium hypochlorite, was effective at concentrations of 1% sodium hypochlorite and above. Cultures did not survive complete drying, which occurred after <3 h at room temperature. B. dendrobatidis was sensitive to heating, and within 4 h at 37°C, 30 min at 47°C and 5 min at 60°C, 100% mortality occurred. UV light (at 1000 mW m-2 with a wavelength of 254 nm) was ineffective at killing B. dendrobatidis in culture.

KEY WORDS: Batrachochytrium dendrobatidis · Disinfectant · Ultraviolet light · Didecyl dimethyl ammonium chloride · DDAC · Desiccation · Sodium hypochlorite

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