Amphibia: Global Amphibian Declines Caused by an Emerging Infectious Disease and Inadequate Immune Responses

Abstract

There are approximately 7000 described species of amphibians in the world, and many are currently in decline. In today’s rapidly developing world, biodiversity loss represents a growing threat to global health, and highly virulent wildlife diseases are emerging with greater frequency. The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has recently become the first known pathogen to cause wildlife extinction on multiple continents, and its uncontrolled spread now threatens the existence of hundreds, if not thousands, of amphibian species. Most amphibians show little resistance to chytridiomycosis, the disease caused by Bd infection, and many fail to develop an adaptive immune response upon reexposure. The greatest contemporary pathway of continued Bd dispersal is the international wildlife trade. The lack of required disease screening and regulation in most countries has allowed for the rapid global emergence of this pathogen, and naïve amphibian populations remain highly vulnerable to decline from Bd introduction. Improved biosecurity policies are urgently needed to prevent immeasurable biodiversity loss and the continued emergence of novel wildlife pathogens.