1. Section of Infectious Diseases1 and
2. Microbiology Research Laboratory,2 Gundersen Lutheran Medical Center, La Crosse, Wisconsin 54601;
3. Wisconsin State Laboratory of Hygiene,3 and
4. Department of Medical Microbiology and Immunology, University of Wisconsin,4 Madison, Wisconsin 53706; and
5. Solvay Animal Health, Inc., Mendota Heights, Minnesota 551205