[1] UNIV CALIF DAVIS, SCH VET MED, ANIM RESOURCES SERV, DAVIS, CA 95616 USA
[2] MONTANA STATE UNIV, DEPT VET MOLEC BIOL, BOZEMAN, MT 59717 USA
[3] UNIV CALIF DAVIS, ANIM COMMUN LAB, DAVIS, CA 95616 USA
[4] USDA ARS, INST LIVESTOCK & POULTRY SCI, PARASITE BIOL & EPIDEMIOL LAB, BELTSVILLE, MD 20705 USA