The North American bullfrog as a reservoir for the spread of Batrachochytrium dendrobatidis in Brazil

Global trade in the North American bullfrog Rana catesbeiana has been implicated in the introduction and spread of the amphibian pathogen Batrachochytrium dendrobatidis. Large-scale production of the North American bullfrog for human consumption has been ongoing since the early part of the 20th century, particularly in Brazil, a pioneer in bullfrog farming following its introduction in the 1930s. In order to determine whether bullfrogs introduced to Brazil and farmed for the food trade serve as reservoirs for amphibian disease, we tested individuals located in the Brazilian states of Sao Paulo and Para to determine the prevalence of B. dendrobatidis infections. We were able to confirm B. dendrobatidis on five farms (78.5% infection prevalence overall) by PCR. Isolates were obtained from three of the five farms and genotyped at 17 loci using multilocus sequence typing. Five isolates from the Brazilian farms were genotypically similar to each other as well as to isolates from Central and South America. Isolates from farmed bullfrogs were more similar to isolates from introduced populations in Venezuela than those from the native range of the bullfrog in eastern North America. These results could have important implications for the origin and spread of B. dendrobatidis in Brazil, its neighboring regions and the conservation of native amphibian fauna. They may also suggest a potential for prior recombination within B. dendrobatidis in bullfrogs, which may have implications for the recent emergence of this pathogen.