Abstract
Infectious diseases are a growing threat to biodiversity, in many cases because of synergistic effects with habitat loss, environmental contamination, and climate change. Emergence of pathogens as new threats to host populations can also arise when novel combinations of hosts and pathogens are unintentionally brought together, for example, via commercial trade or wildlife relocations and reintroductions. Chytrid fungus (Batrachochytrium dendrobatidis) and amphibian ranaviruses (family Iridoviridae) are pathogens implicated in global amphibian declines. The emergence of disease associated with these pathogens appears to be at least partly related to recent translocations over large geographic distances. We experimentally examined the outcomes of novel combinations of host populations and pathogen strains using the amphibian ranavirus Ambystoma tigrinum virus (ATV) and barred tiger salamanders (Ambystoma mavortium, formerly considered part of the Ambystoma tigrinum complex). One salamander population was highly resistant to lethal infections by all ATV strains, including its own strain, and mortality rates differed among ATV strains according to salamander population. Mortality rates in novel pairings of salamander population and ATV strain were not predictable based on knowledge of mortality rates when salamander populations were exposed to their own ATV strain. The underlying cause(s) for the differences in mortality rates are unknown, but local selection pressures on salamanders, viruses, or both, across the range of this widespread host–pathogen system are a plausible hypothesis. Our study highlights the need to minimize translocations of amphibian ranaviruses, even among conspecifc host populations, and the importance of considering intraspecific variation in endeavors to manage wildlife diseases.
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Acknowledgments
National Science Foundation (IBN-9977063, DEB-0213851) funded this research. Animal use was approved under Arizona State University IACUC Protocols 01-589R and 03-670R, and University of Saskatchewan Protocol 20010059. Salamanders were collected under Saskatchewan Environment and Manitoba Conservation Wildlife Research Permits (2001–2003). D.M.S. thanks L. McLeod, M. Scheck, and T. Stitt for their enthusiasm and careful attention to details during the seemingly endless hours of cage changes and long days in the field. We are grateful to several private landowners in Saskatchewan and Manitoba, and to Grasslands National Park, for permission to conduct research on lands they manage.
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Schock, D.M., Bollinger, T.K. & Collins, J.P. Mortality Rates Differ Among Amphibian Populations Exposed to Three Strains of a Lethal Ranavirus. EcoHealth 6, 438–448 (2009). https://doi.org/10.1007/s10393-010-0279-0
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DOI: https://doi.org/10.1007/s10393-010-0279-0