1. Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan.
2. Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan.
3. Department of Natural Resources and Environmental Sciences, University of Illinois, Champaign, Illinois.
4. Program in Ecology and Evolutionary Biology, University of Illinois, Champaign, Illinois.
5. Department of Pathobiology, University of Illinois, Champaign, Illinois.