C-EnterNet Annual Report 2006

...National Integrated Enteric Pathogen Surveillance Program

Table of Contents

• Acknowledgements
• Executive Summary

1. Introduction
   1.1 Background
   1.2 Scope and Content
2. Human Case Summary
   2.1 Overview of Human Cases
   2.2 Outbreak-related Cases
   2.3 Travel-related Cases
   2.4 Endemic Cases
3. Campylobacter
   3.1 Human Cases
   3.2 Exposure Surveillance
   3.3 Integrated Overview
4. Salmonella
   4.1 Human Cases
   4.2 Exposure Surveillance
   4.3 Integrated Overview
5. Pathogenic E. coli
   5.1 Human Cases.....
   5.2 Exposure Surveillance
   5.3 Integrated Overview
6. Yersinia
   6.1 Human Cases
   6.2 Exposure Surveillance
   6.3 Integrated Overview
7. Listeria
   7.1 Human Cases
   7.2 Exposure Surveillance
   7.3 Integrated Overview
8. Parasites
   8.1 Giardiasis
   8.2 Cryptosporidiosis
   8.3 Cyclosporiasis
   8.4 Amoebiasis
9. Episodic Activities
   9.1 Retail Meat Purchasing Trends.
   9.2 Comparison of Travel-associated vs. Non-travel Cases of Enteric Disease
   9.3 Norovirus and Rotavirus in On-farm and Retail Meat samples
   9.4 Towards Understanding Food Flows in the Region of Waterloo
10. Moving Forward

• Appendix A: Questionnaire Results
• Appendix B: Enumeration Results
• Appendix C: Molecular versus Non-molecular Detection Methods

---

Executive Summary

C-EnterNet's 2006 annual report represents a full calendar year of surveillance data collected from the pilot sentinel site - Region of Waterloo - in four component areas including human, retail meat, water and on-farm. This information, in conjunction with the C-EnterNet's 2005 surveillance data, serves as a solid baseline for comparisons with future findings and determination of trends in the occurrence of enteric illness in the human population and pathogen detection in the exposure sources. Molecular subtyping results, which are essential to integrating the results from the four components, have been included in this report. The replication of these activities in additional sentinel sites to represent approximately 10% of the Canadian population will provide national representation of enteric illness in Canada. Although still in its pilot phase, C-EnterNet's integrated surveillance program has produced results that highlight key areas of interest for stakeholders involved in public health and food and water safety issues.

A total of 420 human cases of 10 bacterial, viral and parasitic enteric diseases were reported to the local public health authorities within the pilot sentinel site. One percent (4) of the cases were outbreak-related, 31% (131) were travel-related and 68% (285) were classified as endemic. The four most frequently reported diseases (salmonellosis, campylobacteriosis, giardiasis, verotoxigenic E. coli (VTEC) infection) accounted for 82% of the reported cases.

When the enhanced C-EnterNet surveillance data is compared to historical data in the sentinel site, it appears that overall the prevalence of acute gastro-intestinal illness has been relatively stable over the last decade. Among the most frequent diseases, campylobacteriosis and giardiasis have slightly decreased, while salmonellosis has remained steady. For the less frequent diseases, yersiniosis has gradually increased and the incidence rates for VTEC infection, cryptosporidiosis and Hepatitis A infection were higher over the last couple of years compared to ten years ago.

Travel continues to be associated with enteric disease. Overall, 31% of the human gastrointestinal illness cases in the sentinel site were associated with travelling outside of Canada. However, the proportion of travel-associated cases was higher for some pathogens including Hepatitis A (67%), shigellosis (50%), giardiasis (48%) and salmonellosis (44%). Conversely, cases of E. coli O157:H7 and yersiniosis appeared to be mainly acquired domestically. Some patterns emerged when the travel-related cases were examined according to subtype. For example, 58% of Salmonella Enteritidis infections were contracted abroad, while no travel-associated cases of S. Typhimurium and S. Heidelberg were reported. In addition, while the majority of C. jejuni cases were endemic, the majority of C. coli cases were associated with travelling abroad. In addition, the antimicrobial resistant profiles of the Campylobacter isolates displayed multidrug resistance.

The standardized questionnaires that are the cornerstone of the surveillance program highlighted risk factors that warrant further investigation. For example, reptiles and dogs appear to be potential risk factors for Salmonella and Campylobacter infections, respectively, in humans.

In addition, non-municipal drinking water, swimming in a pool, and visiting a farm animal area appear to be important risk factors for giardia cases in the sentinel site.

C-EnterNet detected pathogens capable of causing human enteric illness on the 3 meat commodities tested, emphasizing the need for proper handling and cooking of raw meat. Following quantitative assessment by the Most Probable Number (MPN) method, a majority of the samples had levels below the limit of detection. These samples most likely represent a lower risk given that the level of these organisms was sufficient for detection using enrichment culture methods, however they were not high enough for enumeration (<0.3 MPN/g).

The subtyping results indicated that in some cases the specific subtypes found on the retail meat were similar to those that caused human illness. For example, for Salmonella Enteritidis, PFGE pattern SENXAI.0038 was the most common Salmonella Enteritidis pattern in retail chicken samples and the most common pattern in endemic human cases. In comparison, Salmonella Enteritidis PFGE pattern SENXAI.0001 was the most common among travel-related human illness and was not detected on any retail meat samples. In addition, C. jejuni was the most common species found on the raw chicken meat and was also the predominant species in human cases. Conversely, some subtypes were of less concern. For example, Salmonella Kentucky was the most common serotype among retail chicken meat samples, however this serotype was not found in any human cases in the sentinel site. Although Yersinia was detected on retail pork samples, further subtyping determined that they were non-pathogenic strains.
Analysis of the retail data for the seasonal occurrence of pathogens resulted in no patterns in Salmonella prevalence. However, the prevalence of Campylobacter on retail chicken meat doubled in the fall of 2006. It is interesting to note that this peak followed the typical rise in human Campylobacter cases seen in the summer months.

Surveillance in the dairy and swine operations in the sentinel site detected some pathogen subtypes known to cause human enteric illness. For example, S. Typhimurium was the top Salmonella serotype in humans and on swine farms, and the second most frequent on dairy farms. Giardia Assemblage B and Cryptosporidium parvum, which are pathogenic to humans, were found in pooled swine and pooled dairy manure samples. Conversely, although pathogenic strains of E. coli were detected in pooled dairy manure samples and untreated surface water, the PFGE subtyping revealed no identical patterns between the human and non-human isolates, suggesting that different strains are circulating in these components. In 2007, the on-farm component has been expanded to include beef and poultry operations in the sentinel site.

Untreated surface water cannot be ignored as a potential exposure route for several enteric pathogens. For example, 13 of the 32 Salmonella isolates had serotypes also found in human cases. In addition, the detection of VTEC, C. jejuni and C. coli demonstrate the potential risk posed by natural recreational water, as a source for human enteric illness. Giardia and Cryptosporidium occurred frequently in untreated surface water, and in the early part of the year there appeared to be a correlation between human endemic cases and the average concentration of Giardia cysts in the untreated surface water. The two most common human pathogenic strains, C. hominis and C. parvum bovine genotype, were detected in untreated surface water samples.

Several episodic studies were conducted in the sentinel site in 2006. A food consumption survey conducted between November 2005 and March 2006 in the sentinel site provided baseline data on food consumption and information about food handling in the healthy population. Results from the survey indicated that the majority (76%) of consumers purchased meat from large chain stores while a smaller proportion (<10%) shopped at non-chain stores (e.g. butcher/independent). In addition, this survey confirmed that the top three purchase choices for residents within the sentinel site were ground beef, pork chops and chicken breasts, supporting the decision made to sample those meats at the retail level.

C-EnterNet data (June 2005 - December 2006) was analyzed to compare enteric disease among travellers (international) and non-travellers (endemic and outbreak cases). Many Salmonella cases (30/64), had been to Mexico and the Caribbean region; the majority of Hepatitis A (7/9) and amoebiasis cases (7/9) reported travelling to Asia; and Giardia cases were most commonly associated with travel to Asia, Mexico and the Caribbean region. Conversely, E. coli O157:H7 appears to be a domestically acquired pathogen as demonstrated by 59 non-travel cases compared to one international travel case.

In collaboration with the Bureau of Microbial Hazards of Health Canada, a short-term study was performed to determine the occurrence of norovirus and rotavirus in retail meat and manure samples from swine and dairy operations within the sentinel site. A human GII.4-like norovirus was detected in the swine and dairy manure and one pork chop, although it was unclear whether this strain is infectious to humans. Rotavirus Group A, a strain capable of causing human illness was found in all types of meat and manure tested.

These highlights from C-EnterNet's activities in 2006 provide a synopsis of the results from this surveillance system. The body of the report provides additional details related to the trends observed during 2006. As the surveillance system progresses to encompass more sentinel sites, data from these activities will produce results that can be generalized to the broader Canadian population. The findings will directly inform national policy on food and water safety, thereby ensuring our ability to maintain Canada's safe food and water supply in the face of new challenges and changes in our environment.