TY - JOUR
T1 - Bullfrog farms release virulent zoospores of the frog-killing fungus into the natural environment
AU - Ribeiro, Luisa P.
AU - Carvalho, Tamilie
AU - Becker, C. Guilherme
AU - Jenkinson, Thomas S.
AU - Leite, Domingos da Silva
AU - James, Timothy Y.
AU - Greenspan, Sasha E.
AU - Toledo, Luís Felipe
N1 - Funding Information:
We thank all bullfrog farm owners for allowing access to specimens and water used in experiments. Thanks to JRG for field assistance and helping me with the statistical analyses, CL for field assistance and figure editing, DMC for contributions in for English grammar and spelling, and CMFM for enabling and assisting the sampling in one of the bullfrog farms. Financial support was provided by grants from the São Paulo State Research Foundation (FAPESP #2016/03344-0; #2016/25358-3), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) and National Council for Scientific and Technological Development (CNPq #300896/2016-6) and US National Science Foundation (DEB-1601259; DBI-1711032). This study was completed in partial fulfilment of the degree of Master of Science by Luisa de Pontes Ribeiro at Universidade Estadual de Campinas (UNICAMP) whose thesis is entitled “Chytrid fungus in bullfrog farms of the state of São Paulo and its implications for native anurans conservation”.
Publisher Copyright:
© 2019, The Author(s).
PY - 2019/12/1
Y1 - 2019/12/1
N2 - Bullfrog farming and trade practices are well-established, globally distributed, and economically valuable, but pose risks for biodiversity conservation. Besides their negative impacts on native amphibian populations as an invasive species, bullfrogs play a key role in spreading the frog-killing fungus Batrachochytrium dendrobatidis (Bd) in the natural environment. Bullfrogs are tolerant to Bd, meaning that they can carry high infection loads without developing chytridiomycosis. To test the potential of bullfrog farms as reservoirs for diverse and virulent chytrid genotypes, we quantified Bd presence, prevalence and infection loads across approximately 1,500 farmed bullfrogs and in the water that is released from farms into the environment. We also described Bd genotypic diversity within frog farms by isolating Bd from dozens of infected tadpoles. We observed individuals infected with Bd in all sampled farms, with high prevalence (reaching 100%) and high infection loads (average 71,029 zoospore genomic equivalents). Average outflow water volume from farms was high (60,000 L/day), with Bd zoospore concentration reaching approximately 50 million zoospores/L. Because virulent pathogen strains are often selected when growing in tolerant hosts, we experimentally tested whether Bd genotypes isolated from bullfrogs are more virulent in native anuran hosts compared to genotypes isolated from native host species. We genotyped 36 Bd isolates from two genetic lineages and found that Bd genotypes cultured from bullfrogs showed similar virulence in native toads when compared to genotypes isolated from native hosts. Our results indicate that bullfrog farms can harbor high Bd genotypic diversity and virulence and may be contributing to the spread of virulent genotypes in the natural environment. We highlight the urgent need to implement Bd monitoring and mitigation strategies in bullfrog farms to aid in the conservation of native amphibians.
AB - Bullfrog farming and trade practices are well-established, globally distributed, and economically valuable, but pose risks for biodiversity conservation. Besides their negative impacts on native amphibian populations as an invasive species, bullfrogs play a key role in spreading the frog-killing fungus Batrachochytrium dendrobatidis (Bd) in the natural environment. Bullfrogs are tolerant to Bd, meaning that they can carry high infection loads without developing chytridiomycosis. To test the potential of bullfrog farms as reservoirs for diverse and virulent chytrid genotypes, we quantified Bd presence, prevalence and infection loads across approximately 1,500 farmed bullfrogs and in the water that is released from farms into the environment. We also described Bd genotypic diversity within frog farms by isolating Bd from dozens of infected tadpoles. We observed individuals infected with Bd in all sampled farms, with high prevalence (reaching 100%) and high infection loads (average 71,029 zoospore genomic equivalents). Average outflow water volume from farms was high (60,000 L/day), with Bd zoospore concentration reaching approximately 50 million zoospores/L. Because virulent pathogen strains are often selected when growing in tolerant hosts, we experimentally tested whether Bd genotypes isolated from bullfrogs are more virulent in native anuran hosts compared to genotypes isolated from native host species. We genotyped 36 Bd isolates from two genetic lineages and found that Bd genotypes cultured from bullfrogs showed similar virulence in native toads when compared to genotypes isolated from native hosts. Our results indicate that bullfrog farms can harbor high Bd genotypic diversity and virulence and may be contributing to the spread of virulent genotypes in the natural environment. We highlight the urgent need to implement Bd monitoring and mitigation strategies in bullfrog farms to aid in the conservation of native amphibians.
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U2 - 10.1038/s41598-019-49674-0
DO - 10.1038/s41598-019-49674-0
M3 - Article
C2 - 31530868
AN - SCOPUS:85072304110
SN - 2045-2322
VL - 9
JO - Scientific Reports
JF - Scientific Reports
IS - 1
M1 - 13422
ER -