Emerging Infectious Diseases and Their Impacts on South American Amphibians

Amphibian chytridiomycosis due to Batrachochytrium dendrobatidis (Bd) and ranaviral disease caused by ranaviruses are two emerging infectious diseases associated with amphibian declines. Both pathogens are widespread in South America, but Ranavirus has been much less studied. Geographically, Bd has highly favorable habitats in the Andes and Atlantic forests. Among the taxa exhibiting high Bd occurrence are Ranidae, Telmatobiidae, Calyptocephalellidae, and Pipidae, reflecting their close association with aquatic environments and therefore higher contact with the infective stage of Bd. Surprisingly, families exhibiting unusually low Bd prevalence comprise species in which lethal chytridiomycosis has caused high impacts, such as Harlequin toads (Atelopus spp.), Andean water frogs (Telmatobius spp.), and Darwin’s frogs (Rhinoderma spp.). Ranavirus-associated die-offs occur frequently in farmed North American bullfrogs (Lithobates catesbeianus; e.g., Brazil and Uruguay), and outbreaks causing high mortality have been described in the Patagonia frog (Atelognathus patagonicus) in Argentina and L. catesbeianus in Brazil. Widespread invasive amphibian species showing high Bd and Ranavirus prevalence are good target species that can be subjected to management for disease mitigation. A better understanding of the epidemiology of Bd and Ranavirus will help guide the prioritization of conservation actions to prevent further biodiversity loss in the world’s most amphibian diverse region.