Phylogeny, Life History, and Ecology Contribute to Differences in Amphibian Susceptibility to Ranaviruses
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Research that identifies the potential host range of generalist pathogens as well as variation in host susceptibility is critical for understanding and predicting the dynamics of infectious diseases within ecological communities. Ranaviruses have been linked to amphibian die-off events worldwide with the greatest number of reported mortality events occurring in the United States. While reports of ranavirus-associated mortality events continue to accumulate, few data exist comparing the relative susceptibility of different species. Using a series of laboratory exposure experiments and comparative phylogenetics, we compared the susceptibilities of 19 amphibian species from two salamander families and five anurans families for two ranavirus isolates: frog virus 3 (FV3) and an FV3-like isolate from an American bullfrog culture facility. We discovered that ranaviruses were capable of infecting 17 of the 19 larval amphibian species tested with mortality ranging from 0 to 100%. Phylogenetic comparative methods demonstrated that species within the anuran family Ranidae were generally more susceptible to ranavirus infection compared to species from the other five families. We also found that susceptibility to infection was associated with species that breed in semi-permanent ponds, develop rapidly as larvae, and have limited range sizes. Collectively, these results suggest that phylogeny, life history characteristics, and habitat associations of amphibians have the potential to impact susceptibility to ranaviruses.
KeywordsAnura Caudata Emerging infectious disease Frog virus 3 Iridoviridae Novel strain Phylogeny Reservoir
We thank the University of Georgia Veterinary Diagnostic and Investigational Laboratory, University of Tennessee Institute of Agriculture, and Tennessee Wildlife Resources Agency (TWRA) for funding this study. We thank C. Baldwin and D. Ingram for providing the virus isolate; N. Hilzinger and L. Whittington for conducting the PCR; and J. Hodges, B. Simpson, M. Campbell, and R. Long for various resources at JARTU. We also thank R. Relyea, J. Hammond, and J. Davenport for providing several species for the experiments. P. Stephens provided insightful comments on the phylogenetic methods. The P. Johnson Lab at the University of Colorado provided helpful feedback on initial drafts of the manuscript. We thank J. Rohr and several anonymous reviewers for helpful comments on the manuscript. All animal husbandry and euthanasia procedures followed an approved University of Tennessee IACUC protocol (#1755). Collection of egg masses was approved by the TWRA (Scientific Collection Permit #1990).
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