[1] US Army, Publ Hlth Ctr, Vet Serv & Publ Hlth Sanitat Directorate, 8252 Blackhawk Rd Bldg E5158, Aberdeen Proving Ground, MD 21010 USA
[2] Colorado State Univ, Coll Vet Med & Biomed Sci, Anim Populat Hlth Inst, 1644 Campus Delivery, Ft Collins, CO 80523 USA
[3] USDA, Anim & Plant Hlth Inspect Serv, Vet Serv, 2150 Ctr Ave, Ft Collins, CO 80526 USA
[4] Colorado State Univ, Coll Vet Med & Biomed Sci, Dept Microbiol Immunol & Pathol, 8110 Microbiol, Ft Collins, CO 80523 USA