Presence of an emerging pathogen of amphibians in introduced bullfrogs Rana catesbeiana in Venezuela

Chytridiomycosis is an emerging fungal disease of amphibians responsible for mass mortalities and population declines globally. One hypothesis for its recent emergence is anthropogenic introduction of the causative agent Batrachochytrium dendrobatidis through trade in amphibians for pets, food and biocontrol. In this study, we examined histological samples from apparently healthy American bullfrogs Rana catesbeiana that have been introduced into the Venezuelan Andes. B. dendrobatidis was present in 96% (46/48) of the individuals examined. In contrast to cases of chytridiomycosis outbreaks, the majority (44/46) of frogs had few, small lesions consistent with little or no clinical disease and no unusual mortality was observed. These findings have implications for amphibian declines in Venezuela and elsewhere. First, the high prevalence of Batrachochytrium but lack of clinical signs or chytridiomycosis-related mortality suggests that R. catesbeiana may be a good reservoir for this parasite in Venezuela. Second, the presence of this emerging pathogen in an introduced amphibian species suggests that trade and introduction of amphibians should be monitored and controlled to halt the spread of this pathogen nationally and internationally. (C) 2004 Elsevier Ltd. All rights reserved.