Chytridiomycosis is an emerging disease responsible for global decline and extinction of amphibians. We report the causative agent, Batrachochytrium dendrobatidis, in North American bullfrogs (Rana catesbeiana) farmed for the international restaurant trade. Our findings suggest that international trade may play a key role in the global dissemination of this and other emerging infectious diseases in wildlife.

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 Sa˜o Paulo and Par´a 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.

Ranaviruses (Iridoviridae) are increasingly associated with mortality events in amphibians, fish, and reptiles. They have been recently associated with mass mortality events in Brazilian farmed tadpoles of the American bullfrog Rana catesbeiana Shaw, 1802. The objectives of the present study were to further characterize the virus isolated from sick R. catesbeiana tadpoles and confirm the etiology in these outbreaks. Sick tadpoles were collected in 3 farms located in Goiás State, Brazil, from 2003 to 2005 and processed for virus isolation and characterization, microbiology, histopathology, and parasitology. The phylogenetic relationships of Rana catesbeiana ranavirus (RCV-BR) with other genus members was investigated by PCR with primers specific for the major capsid protein gene (MCP) and the RNA polymerase DNA-dependent gene (Pol II). Sequence analysis and multiple alignments for MCP products showed > 99% amino acid identity with other ranaviruses, while Pol II products showed 100% identity. Further diagnostics of the pathology including histology and transmission electron microscopy confirmed the viral etiology of these mass deaths. As far as we know, this is the first report of a ranaviral infection affecting aquatic organisms in Brazil. Additionally, our results suggest that American bullfrogs may have served as a vector of transmission of this virus, which highlights the potential threat of amphibian translocation in the world distribution of pathogens. KEY WORDS: Iridovirus · FV3 · Ranavirus · Rana catesbeianaResale or republication not permitted without written consent of the publisher

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