1. Department of Genetics, Franklin College of Arts and Sciences
2. Department of Epidemiology, University of Michigan School of Public Health
3. Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia 30602
4. and Department of Pathology and Unit for Lab Animal Medicine
5. Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109