1. Purdue University School of Veterinary MedicineDepartment of Veterinary Clinical Sciences1248 Lynn HallWest LafayetteIndiana47907‐1248USA
2. Plum Island Animal Disease CenterNAA, ARS, USDA, PO Box 848GreenportNY11944USA
3. Pharmacia Animal Health9613‐190‐2, 7000 Portage RoadKalamazooMichigan49001USA