1 Faculté de médecine vétérinaire, Université de Montréal, 3200 Sicotte, Saint-Hyacinthe, Québec J2S 2M2 (Gottschalk, Lacouture, Fecteau, Desrochers, Boa), Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Saab); National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Japan (Okura).