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。两栖动物壶菌病（Chytridiomycosis）或许是科学界已知的该类现象中最极端的案例。易地放归（translocations）正越来越多地被用于对抗由疾病引发的物种灭绝，但多数此类项目均以失败告终——原因在于疾病仍存续于放归环境中，或是后续在该环境中完成定殖。因此亟需开展真实场景下的研究，以验证环境调控能否通过为病原体营造不利生存条件，提升种群存活率。将受壶菌病影响的两栖动物放归至疾病仍持续存在的环境中，正是检验该研究范式的理想场景。
2. 本研究依托某濒危两栖动物邻近易地放归项目的近似环境条件，开展户外中型生态箱（mesocosms）实验，旨在验证「调控环境盐度可提升两栖动物存活率」这一假说，并解析其内在作用机制。研究将160只感染壶菌、288只未感染的人工繁育幼蛙，投放至16个盐度可控的户外中型生态箱中，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生境中开展，周期为25周，从澳大利亚仲冬持续至次年仲夏。
3. 将盐度从约0.5‰（ppt）提升至3.5~4.5‰，可降低病原体在感染与未感染个体间的传播效率，进而显著降低高盐生态箱中的死亡率：实验进行至23周时，高盐组存活率为0.13，低盐组为0.23。伴随季节变化升高的水温（从平均13℃升至25℃）最终可使所有存活个体清除体内的病原体。
4. 研究结论与应用启示：本研究阐明了环境盐度通过降低疾病传播速率，保护两栖动物宿主免受壶菌病侵害的作用机制；并提出，在当前正开展受壶菌病影响的两栖动物易地放归的区域中调控环境盐度，可提升数百个物种种群存续的概率。从更广泛的视角来看，本研究为「可通过环境调控缓解新兴传染病影响」这一研究范式提供了实证支持。2017年9月18日