Data from: Elevated salinity blocks pathogen transmission and improves host survival for a globally pandemic disease: implications for amphibian translocations

1. Emerging infectious diseases are one of the greatest threats to global biodiversity. Chytridiomycosis in amphibians is perhaps the most extreme example of this phenomenon known to science. Translocations are increasingly used to fight disease-induced extinctions. However, many programs fail because disease is still present or subsequently establishes in the translocation environment. There is a need for studies in real-world scenarios to test whether environmental manipulation could improve survival in populations by generating unfavourable environmental conditions for pathogens. Reintroductions of amphibians impacted by chytridiomycosis into environments where the disease persists provide a scenario where this paradigm can be tested. 2. We tested the hypothesis that manipulating environmental salinity in outdoor mesocosms under near identical environmental conditions applying in a nearby translocation program for an endangered amphibian, would improve survival and determine the mechanisms involved. 160 infected and 288 uninfected, captive-bred, juvenile frogs were released into 16 outdoor mesocosms in which salinity was controlled (high or low salinity treatment). The experiment was run for 25 weeks from the mid-austral winter to the mid-austral summer of 2013 in a temperate coastal environment, Australia. 3. Increasing salinity from ca. 0.5 ppt to 3.5 - 4.5 ppt reduced pathogen transmission between infected and uninfected animals, resulting in significantly reduced mortality in elevated salt mesocosms (0.13, high salt versus 0.23, low salt survival at 23 weeks). Increasing water temperature associated with season (from mean 13oC to 25oC) eventually cleared all surviving animals of the pathogen. 4. Synthesis and applications. We identified a mechanism by which environmental salinity can protect amphibian hosts from chytridomycosis by reducing disease transmission rates and conclude that manipulating environmental salinity in landscapes where chytrid-affected amphibians are currently translocated could improve the probability of population persistence for hundreds of species. More broadly, we provide support for the paradigm that environmental manipulation can be used to mitigate the impact of emerging infectious diseases.18-Sep-2017

1. 新兴传染病是全球生物多样性面临的最严峻威胁之一。两栖动物所患的蛙壶菌病（chytridiomycosis）或许是该现象已知的最极端案例。迁地保护（translocation）正日益被用于对抗由疾病引发的物种灭绝，但多数相关项目最终宣告失败，原因在于病原体仍留存于迁地环境中，或是后续又在该环境内定植。当前亟需开展实地场景下的研究，以验证环境调控能否通过为病原体构建不利生存条件，从而提升种群存活率。将受蛙壶菌病影响的两栖动物重新引入疾病仍持续存在的环境，正是检验这一研究范式的理想场景。
2. 本研究针对某濒危两栖动物的邻近迁地保护项目，在近乎自然的环境条件下开展室外中宇宙实验（mesocosms），旨在验证“调控环境盐度可提升两栖动物存活率”的假说，并解析其背后的作用机制。研究将160只人工繁育的感染幼蛙与288只未感染幼蛙，放归至16个盐度可控的室外中宇宙体系中，设置高盐、低盐两个处理组。实验于2013年在澳大利亚温带沿海区域开展，历时25周，覆盖澳大利亚仲冬至仲夏时段。
3. 将盐度从约0.5千分点（ppt）提升至3.5~4.5千分点，可降低感染个体与未感染个体间的病原体传播效率，进而使高盐中宇宙体系内的死亡率显著降低（实验开展23周时，高盐组存活率为0.13，低盐组为0.23）。伴随季节变化的水温升高（从平均13℃升至25℃），最终清除了所有存活个体体内的病原体。
4. 综合与应用：本研究明确了环境盐度可通过降低疾病传播速率，为两栖动物宿主提供抗蛙壶菌病保护的作用机制，并提出可通过调控受蛙壶菌病影响物种的迁地环境盐度，提升数百种两栖动物的种群存续概率。从更广泛的视角来看，本研究为“环境调控可用于减缓新兴传染病影响”这一研究范式提供了实证支持。
2017年9月18日