1. School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada.
2. Animal Health Centre, British Columbia Ministry of Agriculture, Abbotsford, British Columbia, Canada.
3. Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
4. British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada.
5. St. Paul's Hospital, Vancouver, British Columbia, Canada.
6. Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.