Controlling wildlife fungal disease spread: in vitro efficacy of disinfectants against Batrachochytrium dendrobatidis and Mucor amphibiorum

Abstract

Chytridiomycosis in amphibians, and mucormycosis in the platypus Ornitho rhynchus anatinus and amphibians, are serious fungal diseases affecting these aquatic taxa. In Tasmania, Australia, the fungi that cause these diseases overlap in range along with Phytophthora cinnamomi (Pc), an invasive fungal plant pathogen. To identify disinfectants that may be useful to reduce anthropogenic spread of these fungi to uninfected wilderness areas, for example by bush walkers and forestry or fire-fighting operations, we tested 3 disinfectants and a fire-fighting foam against Mucor amphibiorum (Ma) and tested 1 disinfectant and the foam against Batracho chytrium dendrobatidis (Bd). Combining the present study with previous work we found Bd was more susceptible to all 4 chemicals than Ma. Phytoclean, a disinfectant used at 2 to 10% for 30 s to control Pc, killed cultures of Bd at 0.075% and Ma at 5%, when also applied for 30 s. The disinfectant F10sc was not effective against Ma at standard exposures, but previous work shows Bd is killed at 0.03% with a 1 min exposure. Path-X is effective against Bd at 0.001% with a 30 s exposure and killed Ma at 1% with a 5 min exposure. Forexpan S, a foam added to water at 0.1 to 1% to control forest fires, killed Bd but not Ma when used at 1% for 2 min. Therefore, Phytoclean and Path-X have broader efficacy, although Path-X has not been trialled against Pc. Interestingly a positive mating strain of Ma (from a platypus) was more resistant to disinfectants than a negative strain (from a frog). Current protocols against Pc that involve high concentrations (10%) of Phytoclean are likely to reduce spread of pathogenic wildlife fungi, which is important for protecting biodiversity.KEY WORDS: Chytridiomycosis · Mucormycosis · Pathogenic fungi · Platypus · Amphibian · Phytophthora cinnamomi Resale or republication not permitted without written consent of the publisherDis Aquat Org 99: [119][120][121][122][123][124][125] 2012 the risk of further spread is an important control measure.Mucormycosis, caused by the zygomycete Mucor amphibiorum (Ma), is the most significant disease affecting platypus in Tasmania, although it has not been detected in mainland platypuses (Connolly et al. 1998). In the platypus, infection causes an ulcerative dermatitis, and the fungus may disseminate to internal organs (Obendorf et al. 1993). Infected platypuses can develop impaired thermoregulation and mobility and may die. Mucormycosis also occurs in mainland Australian amphibians but has not been detected in Tasmanian frogs (Connolly et al. 1998). It can cause a fatal, systemic infection in captive and wild frogs and cane toads Bufo marinus , Creeper et al. 1998. A platypus strain of the fungus was able to experimentally infect amphibians (Stewart & Munday 2005). Ma is heterophallic; positive strains produce resistant zygospores if mated with a negative strain, but only positive strains have been found in Tasmania (Schipper 1978, Connolly 2009. Ma also reproduces asexually via infective sporangiospores (Ste...

The platypus: evolutionary history, biology, and an uncertain future

“…Mucormycosis was accidentally introduced to toads and frogs on the Australian mainland (Northern Territory, Queensland, New South Wales) by captive frogs from Melbourne and Perth, but the infection has not been recorded in mainland platypuses. Isolates of M. amphibiorum are susceptible to Amphotericin B and some disinfectants, with some hope of future vaccine development (Connolly et al 1998; Connolly 2009; Webb et al 2012).…”

Parasites in algae mass culture

“…The surfactant Triton-N was proposed for treating algae inoculum before scale-up when it is still a small volume in order to reduce chytrid productivity (Benderliev et al, 1993). Several commercially available disinfectants were found to control the spread of the chytrid infecting amphibians worldwide, Batrachochytrium dendrobatidis (Webb et al, 2012) and may have application to algal mass culture.…”

A rapid and inexpensive viability assay for zoospores and zoosporangia of Batrachochytrium dendrobatidis

“…Laboratory experiments are essential to improve our understanding of this pathogen. Despite its pathogenicity, B. dendrobatidis is easily killed by heat, desiccation (Johnson et al, 2003), disinfectants (Webb et al, 2012), and salt (Stockwell et al, 2012). Therefore, it is often necessary to perform viability estimates on laboratory cultures to determine the proportion of viable cells before commencing experimental work.…”