Bd in the Pyrenees is concentrated into a group of lakes in the Vallee d'Aspe and Ossau. Within this region, one lake in the Ansabere valley, Lescun, has remained Bd free. Lac Lhurs supports a very large population of Alytes, and constitutes one of the main chytridiomycosis-free refuges for these amphibians. However, this has now changed and a low prevalence of infection (~15%) was detected for the first time in 2009. This year, 2010, infection with Bd has increased dramatically to 100% and the first chytridiomycosis mortalities were observed in September. We are still unclear about the mechanism that Bd uses to spread between lakes: Lac Lhurs is shielded from other valleys by a cirque of high peaks that may have limited vector-borne transmission via birds or other vertebrates. This may explain why the Lac remained uninfected in this heavily-infected region for so long. How did Bd arrive? As with so many other aspects of this enigmatic pathogens life-history, we do not know. However, we do know that this otherwise pristine population of amphibians now faces an uncertain future.
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