Chytridiomycosis, caused by the Batrachochytrium dendrobatidis fungus, has caused the most significant disease-driven vertebrate extinction wave in recorded history.
Amphibians infected with chytrid develop thickened, peeling skin, lethargy, loss of righting reflex, and death. The disease process involves disruption of skin function causing fatal electrolyte imbalance. Infected wild animals suffer in isolation without treatment. The scale of individual animal suffering across hundreds of affected species is immense, even if less visible than mammalian disease events.