Out of Africa? On the origin of amphibian chytridiomycosis.

Abstract

Amphibian chytridiomycosis is an emerging infectious disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). This pathogen is known to infect over 200 species of anurans and caudates, and has been associated with amphibian population declines and extinctions. Current evidence indicates that the pathogen has been recently introduced into new areas from an area of enzootic infection, and that the international trade of amphibians has been involved in the wide spread of the disease. We developed a novel, non-destructive method for the retrospective assessment of archived museum amphibians in order to test the hypothesis that Bd originated from Africa. The earliest case of Bd infection was found in a specimen of X. laevis bunyoniensis collected in 1935 in Uganda, and we suggest that by the 1930s Bd infection was widely established in sub-Saharan Africa. The finding of five cases of Bd infection from three species of Xenopus, the low levels of infection and the stable prevalence over the time detected, indicate that an historical equilibrium between Xenopus spp. and Bd infection have existed in Africa.