An International Outbreak of Salmonellosis Associated with Raw Almonds Contaminated with a Rare Phage Type of Salmonella Enteritidis
Abstract:During the winter of 2000 to 2001, an outbreak due to Salmonella Enteritidis (SE) phage type 30 (PT30), a rare strain, was detected in Canada. The ensuing investigation involved Canadian and American public health and food regulatory agencies and an academic research laboratory. Enhanced laboratory surveillance, including phage typing and pulsed-field gel electrophoresis, was used to identify cases. Case questionnaires were administered to collect information about food and environmental exposures. A case-control study with 16 matched case-control pairs was conducted to test the hypothesis of an association between raw whole almond consumption and infection. Almond samples were collected from case homes, retail outlets, and the implicated processor, and environmental samples were collected from processing equipment and associated farms for microbiological testing. One hundred sixty-eight laboratory-confirmed cases of SE PT30 infection (157 in Canada, 11 in the United States) were identified between October 2000 and July 2001. The case-control study identified raw whole almonds as the source of infection (odds ration, 21.1; 95% confidence interval, 3.6 to ∞). SE PT30 was detected in raw whole natural almonds collected from home, retail, distribution, and warehouse sources and from environmental swabs of processing equipment and associated farmers' orchards. The frequent and prolonged recovery of this specific organism from a large agricultural area was an unexpected finding and may indicate significant diffuse contamination on these farms. Identification of almonds as the source of a foodborne outbreak is a previously undocumented finding, leading to a North American recall of this product and a review of current industry practices.
Document Type: Abstract
Affiliations: 1: Foodborne, Waterborne and Zoonotic Infections Division, Centre for Infectious Disease Prevention and Control, Health Canada, 160 Research Lane, Unit 206, Guelph, Ontario, Canada N1G 5B2 2: Central Public Health Laboratory, Laboratories Branch, Ministry of Health and Long-Term Care, Province of Ontario, 81 Resources Road, Etobicoke, Ontario, Canada M9P 3T1 3: Food and Drug Branch, California Department of Health Services, 601 North 7th Street, MS 357, P. O. Box 942732, Sacramento, California 94234, USA 4: National Laboratory of Enteric Pathogens, National Microbiology Laboratory, Health Canada, 1015 Arlington Street, Winnipeg, Manitoba, Canada R3E 3R2 5: Disease Control Service, Public Health Branch, Ministry of Health and Long-Term Care, Province of Ontario, 5700 Yonge Street, 8th Floor, Toronto, Ontario, Canada M2M 4K5 6: Foodborne, Waterborne and Zoonotic Infections Division, Centre for Infectious Disease Prevention and Control, Health Canada, 160 Research Lane, Unit 206, Guelph, Ontario, Canada N1G 5B2 and Canadian Field Epidemiology Program, Population and Public Health Branch, Health Canada, 130 Colonnade Road, AL 6503A, Ottawa, Ontario, Canada K1A 0K9 7: Department of Food Science and Technology, University of California, One Shields Avenue, Davis, California 95616, USA 8: Canadian Food Inspection Agency, 3155 Willingdon Green, Burnaby, British Columbia, Canada V5G 4P2 9: Canadian Field Epidemiology Program, Population and Public Health Branch, Health Canada, 130 Colonnade Road, AL 6503A, Ottawa, Ontario, Canada K1A 0K9 10: U.S. Food and Drug Administration, 5600 Fishers Lane, HFC-160 Room 12A55, Rockville, Maryland 20857, USA 11: Epidemic Intelligence Service, Division of Applied Public Health Training, Epidemiology Program Office, Centers for Disease Control, 1600 Clifton Road, MS-A-38, Atlanta, Georgia 30333, USA and Foodborne and Diarrheal Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, MS-C-14, 1600 Clifton Road, MS-A- 38, Atlanta, Georgia 30333, USA 12: Vancouver Island Health Authority, 2-2631 Quadra Street, Victoria, British Columbia, Canada V8T 4E2 13: Provincial Epidemiology Service, Department of Health and Wellness, Province of New Brunswick, 520 King Street, 2nd Floor, Carleton Place, Fredericton, New Brunswick, Canada E3A 3N6