Amphibian conservation goals depend on effective disease-treatment protocols. Desirable protocols are species, life stage, and context specific, but currently few treatment options exist for amphibians infected with the chytrid fungus Batrachochytrium dendrobatidis (Bd). Treatment options, at present, include antifungal drugs and heat therapy, but risks of toxicity and sideeffects make these options untenable in some cases. Here, we report on the comparison of several novel treatments with a more generally accepted antifungal treatment in experimental scientific trials to treat Bd-infected frogs including Alytes obstetricans tadpoles and metamorphs, Bufo bufo and Limnodynastes peronii metamorphs, and Lithobates pipiens and Rana muscosa adults. The experimental treatments included commercial antifungal products (itraconazole, mandipropamid, steriplantN, and PIP Pond Plus), antimicrobial skin peptides from the Bd-resistant Pelophylax esculentus, microbial treatments (Pedobacter cryoconitis), and heat therapy (35°C for 24 h). None of the new experimental treatments were considered successful in terms of improving survival; however, these results may advance future research by indicating the limits and potential of the various protocols. Caution in the use of itraconazole is warranted because of observed toxicity in metamorphic and adult frogs, even at low concentrations. Results suggest that rather than focusing on a single cure-all, diverse lines of research may provide multiple options for treating Bd infection in amphibians. Learning from 'failed treatments' is essential for the timely achievement of conservation goals and one of the primary aims for a publicly accessible treatment database under development.

Emerging infectious diseases can drive host populations to extinction and are a major driver of biodiversity loss. Controlling diseases and mitigating their impacts is therefore a priority for conservation science and practice. Chytridiomycosis is a devastating disease of amphibians that is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), and for which there is an urgent need to develop mitigation methods. We treated tadpoles of the common midwife toad (Alytes obstetricans) with antifungal agents using a capture-treat-release approach in the field. Antifungal treatment during the spring reduced the prevalence of Bd in the cohort of tadpoles that had overwintered and reduced transmission of Bd from this cohort to the uninfected young-of-the-year cohort. Unfortunately, the mitigation was only transient, and the antifungal treatment was unable to prevent the rapid spread of Bd through the young-of-the year cohort. During the winter, Bd prevalence reached 100% in both the control and treated ponds. In the following spring, no effects of treatment were detectable anymore. We conclude that the sporadic application of antifungal agents in the present study was not sufficient for the long-term and large-scale control of Bd in this amphibian system.

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) is sensitive to high temperature. Hence, exposing amphibians to high temperature may be a method to clear Bd infection. However, the effect of exposure to elevated temperature has never been tested in larval stages or temperate species.We experimentally exposed tadpoles of the toad Alytes obstetricans to low, medium and high temperatures and found that most, but not all, tadpoles lost the infection when exposed to temperatures higher than 26•C for 5 days. Thus, exposure to elevated temperatures can be used to treat tadpoles against Bd infection. Abstract. The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) is sensitive to high temperature. Hence, exposing amphibians to high temperature may be a method to clear Bd infection. However, the effect of exposure to elevated temperature has never been tested in larval stages or temperate species. We experimentally exposed tadpoles of the toad Alytes obstetricans to low, medium and high temperatures and found that most, but not all, tadpoles lost the infection when exposed to temperatures higher than 26 • C for 5 days. Thus, exposure to elevated temperatures can be used to treat tadpoles against Bd infection.

The fungus Batrachochytrium dendrobatidis (Bd), which is the etiological agent of the disease chytridiomycosis, is threatening both wild and captive amphibians. While there are some methods of treating amphibians in captivity, no method has yet been shown to be a promising treatment for amphibian populations in natural habitats. Here we present the results of a laboratory experiment in which we tested 2 antifungal agents that might be used to treat amphibians in the field. As a first step towards the goal of developing mitigation methods, we tested the efficiency of these agents in reducing Bd prevalence and loads (zoospore counts) in the laboratory. We exposed naturally infected tadpoles of the midwife toad Alytes obstetricans to different concentrations of the antifungal agents for 7 d. We found that Virkon Aquatic® affected neither Bd prevalence nor loads. At 0.625 ml l-1 of General Tonic®, prevalence was reduced to 60%, and infected animals had greatly reduced burdens. However, tadpole length was reduced by 19% and mass by 32% on average compared to the control group, suggesting a negative effect on fitness. Tadpole survival was not affected at 0.625 ml l-1 or 1.25 ml l-1, but was reduced to 60% at 2.5 ml l-1. Keeping animals in a dilution of General Tonic® for 7 d at a concentration of 0.625 ml l-1 might be an easy way to reduce zoospore counts in large numbers of animals at relatively low cost.

In three Bavarian populations of Alytes obstetricans that were studied for the occurrence of Batracirociiytrium dendrobatidis, the pathogen was detected. This is the first account of chytridiomycosis in Bavaria, Germany. Infected tadpoles had low infection loads mostly of lO' to 10^ genome equivalents. Under high-density rearing conditions in the laboratory mortality rates were high after metamorphosis. Some individuals, however, showed no infection with Bd, while others survived metamorphosis in spite of low Bd loads. A new approach was chosen to get historical data on Bd occurrence in one of these populations: skeletochronological phalanx cross sections of 248 individuals that had been collected in the late 1980s were used to analyse the epidermis for chytrid sporangia. No sporangia were detected, thus we conclude that this population was not affected by Bd in the past.