[1] Boehringer Ingelheim GmbH & Co KG, Ingelheim, Germany
[2] Univ Copenhagen, Dept Vet Anim Sci, Copenhagen, Denmark
[3] Varigen Biosci Corp, Madison, WI USA
[4] USDA, Anim & Plant Hlth Inspect Serv, Natl Vet Serv Labs, Diagnost Bacteriol & Pathol Lab, Ames, IA USA
[5] Univ Guelph, Sch Environm Sci, Guelph, ON, Canada