Integrated surveillance and potential sources of Salmonella enteritidis in human cases in Canada from 2003 to 2009

Abstract

Salmonella enteritidis has emerged as the most prevalent cause of human salmonellosis in Canada. Recent trends of S. enteritidis subtypes and their potential sources were described by integrating Salmonella data from several Canadian surveillance and monitoring programmes. A threefold increase in S. enteritidis cases from 2003 to 2009 was identified to be primarily associated with phage types 13, 8 and 13a. Other common phage types (4, 1, 6a) showed winter seasonality and were more likely to be associated with cases linked to international travel. Conversely, phage types 13, 8 and 13a had summer seasonal peaks and were associated with cases of domestically acquired infections. During agri-food surveillance, S. enteritidis was detected in various commodities, most frequently in chicken (with PT13, PT8 and PT13a predominating). Antimicrobial resistance was low in human and non-human isolates. Continued integrated surveillance and collaborative prevention and control efforts are required to mitigate future illness.

Fig. 1

Laboratory-confirmed Salmonella Enteritidis case incidence rate (per 100 000) and proportion among all non-typhoidal Salmonella isolates, by year, in Canada, 2003–2009 (source: National Enteric Surveillance Program).

Fig. 2

Laboratory-confirmed Salmonella Enteritidis case incidence rate (per 100 000), by year and province/territory, in Canada, 2003–2009 (source: National Enteric Surveillance Program). YT, Yukon Territory; NT, Northwest Territory; NU, Nunavut; BC, British Columbia; AB, Alberta; SK, Saskatchewan; MB, Manitoba; ON, Ontario; QU, Québec; NB, New Brunswick; NS, Nova Scotia; PEI, Prince Edward Island; NL, Newfoundland.

Fig. 3

Salmonella Enteritidis PT8, PT13a and PT13 isolates by month, Canada 2003–2009 (source: National Microbiology Laboratory and outbreak identifications, Outbreak Management Division, Centre for Food-borne, Environmental, and Zoonotic Infectious Diseases, Public Health Agency of Canada and Provincial Public Health Authorities).

Fig. 4

Monthly actual and predicted numbers of S. Enteritidis cases for phage types 13, 8 and 13a, in Canada, 2003–2009 (source: National Microbiology Laboratory). The predicted values are the result of modelling the data using a negative binomial regression and assist in predicting seasonality.

Fig. 5

Monthly actual and predicted numbers of S. Enteritidis cases for phage types 1, 4 and 6a, in Canada, 2003–2009 (source: National Microbiology Laboratory). The predicted values are the result of modelling the data using a negative binomial regression and assist in predicting seasonality.

Fig. 6

Common S. Enteritidis phage types recovered in humans and non-humans, by year, in Canada, 2003–2009 [sources: National Microbiology Laboratory, Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) and C-EnterNet]. * CIPARS data only. † CIPARS and C-EnterNet data combined. ‡ C-EnterNet data only.