1. Environmental Medicine Consortium and Department of Clinical Sciences, North Carolina State University, 4700 Hillsborough Street, Raleigh, North Carolina 27606, USA
2. The Marine Mammal Center, Marin Headlands, Sausalito, California 94965, USA
3. Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, California 95616, USA