1. Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA
2. Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA
3. U.S. Geological Survey, National Wildlife Health Center, Madison, WI 53711, USA
4. Smithsonian Tropical Research Institute, Balboa Ancón, Panama