Batrachochytrium dendrobatidis fungus has caused the most devastating infectious disease wildlife die-off in recorded history, with profound welfare implications for affected amphibians.
Chytrid disease causes a prolonged and progressive death for affected amphibians. The disruption of skin osmotic function causes animals to become progressively weaker as electrolyte balance fails, leading to muscle cramping, inability to move normally and ultimately cardiac arrest. Affected animals show abnormal behaviour including basking at unusual times and loss of normal escape responses that suggest they are experiencing significant distress before death. The scale of population losses represents welfare catastrophe at the population level - entire species of sentient beings eliminated by a single introduced pathogen. Ex-situ conservation programmes that preserve species from extinction provide welfare benefit by enabling future reintroduction to disease-free or resistance-selected populations.