1. Office of Animal Welfare, University of Pennsylvania, Philadelphia, Pennsylvania
2. Division of Comparative Medicine, University of Oklahoma Health Services Center, Oklahoma City, Oklahoma
3. University Laboratory Animal Resources, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
4. University Laboratory Animal Resources, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania;, Email: marx@upenn.edu