Chytridiomycosis caused by Batrachochytrium dendrobatidis has driven over 200 amphibian species to extinction or population collapse, representing the greatest infectious disease impact on vertebrates ever recorded.
Frogs dying from chytridiomycosis experience a prolonged disease process involving skin dysfunction, electrolyte imbalance, lethargy, and ultimately cardiac failure. While individual frog sentience is debated, the scale of the crisis — hundreds of millions of individual animals across hundreds of species — and the ecological collapse it causes represents both a direct welfare concern and a massive indirect welfare harm to the ecosystems these animals support. Prevention through biosecurity protocols limiting Bd spread between habitats is the most effective available response.