I discovered why seemingly healthy amphibians were being wiped out
theguardian.com
theguardian.com
I'll add that there are lots of other causes of mass amphibian extinctions, usually tied to localized habitat destruction and/or climate change: https://blaustein.science.oregonstate.edu/pdfs/Kiesecker_200.... These causes also increase the susceptibility of amphibians to various pathogens/disease.