Chytridiomycosis, an infectious disease of amphibians caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), poses an imminent conservation threat. The global spread of Bd has led to mass mortality events in many amphibian species, resulting in at least 90 species' extinctions to date. Exposure to Bd metabolites (i.e. non-infectious antigenic chemicals released by Bd) partially protects frogs during subsequent challenges with live Bd, suggesting its use as a prophylactic treatment and potential vaccine. However, we do not know whether Bd metabolite exposure protects against strains beyond the one used for treatment. To address this knowledge gap, we conducted a 3 × 2 experiment where we exposed adult Cuban treefrogs, Osteopilus septentrionalis, to one of three treatments (Bd metabolites from California-isolated strain JEL-270, Panamá-isolated strain JEL-419, or an artificial spring water control) and then challenged individuals with live Bd from either strain. We found that exposure to Bd metabolites from the California-isolated strain significantly reduced Bd loads of frogs challenged with the live Panamá-isolated strain, but no other treatments were found to confer protective effects. These findings demonstrate asymmetric cross-protection of a Bd metabolite prophylaxis and suggest that work investigating multiple, diverse strains is urgently needed.

壶菌病是一种由真菌病原体Batrachochytrium dendrobatidis (Bd)引起的两栖动物传染病，对保护构成迫在眉睫的威胁。Bd 的全球传播导致许多两栖动物物种的大规模死亡事件，迄今已导致至少 90 种物种灭绝。暴露于 Bd 代谢物（即 Bd 释放的非感染性抗原化学物质）在随后的活 Bd 攻击期间部分保护青蛙，表明其可用作预防性治疗和潜在疫苗。然而，我们不知道 Bd 代谢物暴露是否可以防止超出用于治疗的菌株。为了解决这个知识差距，我们进行了一个 3 × 2 的实验，我们暴露了成年古巴树蛙Osteopilus septentrionalis，到三种处理中的一种（来自加利福尼亚分离菌株 JEL-270、巴拿马分离菌株 JEL-419 的 Bd 代谢物或人工泉水对照），然后用来自任一菌株的活 Bd 挑战个体。我们发现，暴露于加利福尼亚分离株的 Bd 代谢物显着降低了受到巴拿马分离株活体攻击的青蛙的 Bd 负荷，但没有发现其他治疗方法具有保护作用。这些发现证明了 Bd 代谢物预防的不对称交叉保护，并表明迫切需要研究多种不同菌株的工作。