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Canadian Integrated Surveillance Report: Salmonella, Campylobacter,
pathogenic E. coli and Shigella, from 1996 to 1999 

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Background 

Participants at the National Consensus Conference on Foodborne, Waterborne and Enteric Disease Surveillance, held in Ottawa, November 1995, recommended the development of a report showing trends in enteric disease in Canada. Another of their recommendations - a survey of local, provincial/territorial, federal, industry and academic stakeholders - was conducted in 1997 to identify the information needs and format preferences of these stakeholders for such a report. The results of that survey were used to develop the first integrated report, which covered Salmonella, Campylobacter and pathogenic E. coli, for 1995. Except for outbreak events, the changes in enteric disease incidence are gradual and become more evident when data are compared across multiple years. Therefore, the current report covers data for the subsequent 4 years, 1996 to1999. 

The databases used to prepare this report were developed for different reasons and contain different data elements (see the Appendix for details). In general, notification of a case of enteric disease is initiated with the laboratory confirmation of a notifiable agent. The local public health unit is informed of the case by the laboratory or physician and through subsequent follow-up acquires detailed information about the patient and the potential risk factors. These data form the basis of reports in the National Notifiable Diseases Summary (NNDS) dataset and the National Notifiable Diseases Individual Case (NNDI) dataset. Local and regional laboratories forward some enteric pathogens to provincial/territorial laboratories for confirmation and identification. Provincial/territorial laboratories send summary information from cases associated with these isolates to the National Enteric Surveillance Program (NESP). As well, they send some isolates to the National Laboratory for Enteric Pathogens (NLEP) for identification and additional subtyping. Isolates from non-human sources (food, animals and the environment) are sent to the Laboratory for Foodborne Zoonoses (LFZ) for subtyping and confirmation. An additional source of data is the Discharge Abstract Database (DAD) from the Canadian Institute for Health Informatics (CIHI), which contains data about hospital admissions from across the nation. Thus, each database provides a unique perspective on enteric diseases in Canada. 

This report uses all of these databases to describe agents, cases and outbreaks related to the top four enteric bacterial groups reported in Canada - Salmonella, Campylobacter, pathogenic Escherichia coli and Shigella. These data, from passive surveillance systems and a medical records abstract system, represent the best national data held in Canada for enteric disease. However, as each system has inherent limitations, the data should be interpreted with these limitations in mind (see Appendix for more information). 

Although the main focus of this document is to describe disease trends over time and geographic area, comparisons among the main surveillance systems collecting similar data have been highlighted. For instance, the rates of infection with Salmonella are quite similar whether reported as National Notifiable Diseases data or as laboratory based data (NLEP/NESP). For Campylobacter infections, however, the rates can be quite different depending on the data source and the province/territory. No single data source is adequate to describe all the various aspects of enteric disease in Canada. By combining the interpretation of these data sets, this document provides a comprehensive overview of enteric disease as well as an indication of which data source would be the most useful for answering particular questions about the occurrence of enteric diseases in Canada.