1. Department of Pharmacology and Toxicology Faculty of Veterinary Medicine University of Warmia and Mazury Olsztyn 10‐718 Poland
2. Department of Infectious Diseases & Immunology College of Veterinary Medicine University of Florida Gainesville FL 32611‐0880 USA
3. Department of Microbiology and Immunology Montana State University Bozeman MT 59715 USA