His research focuses on the epidemiology of foodborne infections in animals and humans, including antimicrobial resistance. Since 1986 he has supervised over 60 MSc and PhD students. He is author or co-author of over 280 publications in refereed scientific journals and several book chapters. He consulted on technical matters with several organizations at the provincial, national and international levels, notably the Public Health Agency of Canada, Health Canada, the United States Food and Drug Administration, the Centers for Disease Control and the World Health Organization (WHO). He chaired Health Canada’s Advisory Committee on Animal Uses of Antimicrobials and Impact on Resistance and Human Health 1999-2002. He also chaired the World Health Organization’s evaluation of the termination of the use of antimicrobial growth promoters in Denmark, the FAO/OIE/WHO Expert Workshop on Non-human Antimicrobial Usage and Antimicrobial Resistance: Scientific Assessment and the Joint FAO/WHO/OIE Expert Meeting on Critically Important Antimicrobials. He participated on the Guideline Development Committee of the WHO guidelines on use of medically important antimicrobials in food-producing animals.