[1] Univ Minnesota, Coll Vet Med, Dept Vet Populat Med, 225 VMC,1365 Gortner Ave, St Paul, MN 55108 USA
[2] USDA, NAHMS, APHIS, VS,CEAH, 2150 Ctr Ave,Bldg B-2E7, Ft Collins, CO 80526 USA
[3] Mississippi State Univ, Coll Vet Med, Dept Pathobiol & Populat Med, Mississippi State, MS 39762 USA