The University of Queensland, School of Biological Sciences, St. Lucia, QLD 4072, Australia.
University of Pittsburgh, Department of Biological Sciences, Pittsburgh, PA, 15260, United States.
Sci Rep. 2017 Jun 14;7(1):3529. doi: 10.1038/s41598-017-03605-z.
The fungal pathogen Batrachochytrium dendrobatidis (Bd) has been implicated in amphibian population declines globally. Given that Bd infection is limited to the skin in post-metamorphic amphibians, routine skin sloughing may regulate infection. Skin sloughing has been shown to reduce the number of cultivatable microbes on amphibian skin, and Bd infection increases skin sloughing rates at high loads. However, it is unclear whether species specific differences in skin sloughing patterns could regulate Bd population growth on the skin, and influence subsequent infection dynamics. We exposed five Australian frog species to Bd, and monitored sloughing rates and infection loads over time. Sloughing reduced Bd load on the ventral skin surface, in all five species, despite wide variation in susceptibility to disease. In the least susceptible species, an increase in sloughing rate occurred at lower infection loads, and sloughing reduced Bd load up to 100%, leading to infection clearance. Conversely, the drop in Bd load with sloughing was only temporary in the more susceptible species. These findings indicate that the ability of sloughing to act as an effective immune defence is species specific, and they have implications for understanding the pattern of Bd population growth on individual hosts, as well as population-level effects.
真菌病原体蛙壶菌（Batrachochytrium dendrobatidis，Bd）已被认为与全球范围内的两栖动物种群减少有关。由于 Bd 感染仅限于变态后两栖动物的皮肤，因此常规的皮肤脱落可能会调节感染。皮肤脱落已被证明可以减少两栖动物皮肤上可培养微生物的数量，并且在高负荷下 Bd 感染会增加皮肤脱落率。然而，目前尚不清楚皮肤脱落模式的物种特异性差异是否可以调节皮肤表面的 Bd 种群增长，并影响随后的感染动态。我们将五种澳大利亚青蛙物种暴露于 Bd 中，并随时间监测脱落率和感染负荷。尽管对疾病的敏感性存在广泛差异，但在所有五种物种中，皮肤脱落都降低了腹侧皮肤表面的 Bd 负荷。在最不敏感的物种中，在较低的感染负荷下，脱落率增加，并且皮肤脱落可将 Bd 负荷降低多达 100%，导致感染清除。相反，在更敏感的物种中，脱落导致 Bd 负荷下降只是暂时的。这些发现表明，脱落作为有效免疫防御的能力是物种特异性的，这对理解 Bd 在个体宿主上的种群增长模式以及种群水平的影响具有重要意义。
