American Bullfrogs (Lithobates catesbeianus) Resist Infection by Multiple Isolates of Batrachochytrium dendrobatidis, Including One Implicated in Wild Mass Mortality

Abstract

The emerging amphibian disease chytridiomycosis varies in severity depending on host species.Within species, disease susceptibility can also be influenced by pathogen variation and environmental factors.Here, we report on experimental exposures of American bullfrogs (Lithobates catesbeianus) to three different isolates of Batrachochytrium dendrobatidis (Bd), including one implicated in causing mass mortality of wild American bullfrogs. Exposed frogs showed low infection prevalence, relatively low infection load, and lack of clinical disease. Our results suggest that environmental cofactors are likely important contributors to Bdassociated American bullfrog mortality and that this species both resists and tolerates Bd infection.

Pathogenic fungus in feral populations of the invasive North American bullfrog in Argentina

“…The infected individuals analyzed in this study showed no evident signs of chytridiomycosis, supporting the findings of Daszak et al (13) and eskew et al (26). Although the cycle threshold for positive results indicated moderate to minimal amounts of Bd DNA in the samples (23), bullfrogs become reservoirs and potential vectors of Bd to native cohabitant species.…”

“…Experimental data show that L. catesbeianus is among the species capable of being infected by Bd without progression of clinical signs or death (13,26). The infected individuals analyzed in this study showed no evident signs of chytridiomycosis, supporting the findings of Daszak et al (13) and eskew et al (26).…”

Rapid extirpation of a North American frog coincides with an increase in fungal pathogen prevalence: Historical analysis and implications for reintroduction

“…H. regilla and R. catesbeiana may have provided sufficient reservoir hosts to allow for Bd persistence in the system, facilitating chytridiomycosis-induced extinction of R. boylii. While some laboratory studies have suggested that bullfrogs may not always make suitable reservoir hosts for Bd(Eskew, Worth, Foley, & Todd, 2015;Gervasi et al, 2013), our observation that bullfrogs have the highest Bd prevalence and loads among species sampled in the field(Figure 7), and previous work showing that bullfrog sympatry is an important predictor of Bd infection in R. boylii(Adams et al, 2017), supports the hypothesis that bullfrogs are a vector of Bd in California, including where R. boylii are extant.Bullfrog farming may have played a key role in introducing and spreading Bd in California. Bullfrogs were brought to California in the early 20th century from the eastern United States, where Bd may have occurred in an enzootic state for much longer than in the western United States(Talley, Muletz, Vredenburg, Fleischer, & Lips, 2015).…”

“…boylii . While some laboratory studies have suggested that bullfrogs may not always make suitable reservoir hosts for Bd (Eskew, Worth, Foley, & Todd, ; Gervasi et al., ), our observation that bullfrogs have the highest Bd prevalence and loads among species sampled in the field (Figure ), and previous work showing that bullfrog sympatry is an important predictor of Bd infection in R . boylii (Adams et al., ), supports the hypothesis that bullfrogs are a vector of Bd in California, including where R .…”

Interactions between amphibian skin sloughing and a cutaneous fungal disease: infection progression, immune defence, and phylogenetic patterns

“…There is little definitive evidence of species demonstrating widespread resistance to chytridiomycosis, but some species appear to demonstrate greater resistance than most, including the notorious invader Lithobates catesbeianus (Gervasi et al 2013;Eskew et al 2015), and threatened species in the genus Leiopelma (Bishop et al 2009;), amongst others (Woodhams et al 2007a;Gahl et al 2012;Searle et al 2011b). Furthermore, additional species are thought to be largely tolerant to infection, most notably the common laboratory species Xenopus laevis from Africa (Ramsey et al 2010;Van Rooij et al 2012), and…”