This case study was a successful learning exercise that employed PE techniques in a developed world context. The information collected from each interview and focus group provided a helpful starting point to begin answering our three research questions. The majority of discussions were about contributing factors (risk and susceptibility factors) and the interactions that exist between them. Other information obtained related to observations of comfort levels with certain topics, and the impact of regional differences and public health experience when determining the MLSI.
When asked about important contributing factors for infection with common enteric pathogens, informants identified a multitude of risk and susceptibility factors (Table 2). The factors most commonly discussed fell under the key themes of food handling (e.g. cross contamination, undercooked food, and improper temperature control) and behaviours (e.g. personal hygiene practices). The importance of these contributing factors was consistent with the findings of a previous study that examined public health inspector perceptions of food safety issues . The key theme geography was not discussed in as much detail. A study conducted by Papadopoulos et al.  described the same phenomenon when researching risk factors for campylobacteriosis. Informants from that study, as well as the current study, focused on human behaviours and acknowledged that individuals often perceive their food purchases to be safe, and their risk of infection to be low when preparing foods within the home . These findings are consistent with another Ontario report that found over 50% of sporadic enteric cases to be associated with risk behaviours within the home (e.g. unsafe food handling) . The lack of emphasis placed on geography may also have been the result of informants having limited professional experience with contributing factors outside of human behaviour.
Factors contributing to enteric disease often do not act independently, but affect and are affected by many other factors. From the multitude of factors identified by our informants, three complexity diagrams were created to help illustrate some of these associations (Figure 2). The highlighted complexities that exist between the contributing factors and key themes suggests that when study enteric disease there is a need for more holistic approaches that recognise those important interconnections. Similar research supports this concept by acknowledging that enteric disease is a complicated process given the existing interactions and number of ways an individual can acquire an infection , .
The level of comfort informants had with the topic and the clarity of the questions being asked influenced the relative importance of identified contributing factors. For instance, in one focus group, men having sex with men was introduced as a potential contributing factor but the group quickly dismissed this idea and moved on to list other factors. We hypothesize this was because informants were uncomfortable discussing this subject with their colleagues. However, sexual behaviours such as men having sex with men have been identified as important risk factors for some enteric pathogens (e.g. Giardia) . As previously mentioned, informants were also uncomfortable discussing culture and ethnicity. This discomfort was primarily observed in focus group discussions. Informants explained that culture/ethnicity information is not collected by surveillance groups, and therefore felt like they were speculating. For example, one informant stated: “I feel like we’re being prejudicial.” While focus group informants were visibly uncomfortable, the interviewed public health inspectors appeared more open and willing to explore this topic. This may be attributed to the fact that investigators at local health regions have daily exposures to cultural/ethnical differences when investigating enteric disease cases and outbreaks. Group dynamics may have also contributed; semi-structured interviews were conducted with individual investigators whereas in the focus groups informants who stated their opinions and perspectives did so in front of their colleagues.
Informants struggled to explore geography as a theme within the context of Southern Ontario. In one focus group, they expressed that the theme was too limiting given the similar climate and geography across Southern Ontario. While there was uncertainty regarding how deeply this topic was probed, informants went on to explore this theme in terms of a more spatial or environmental context, identifying location clusters or ‘hot spots’ (e.g. hospitals or agricultural centres), seasonality, and differences in contributing factors between urban and rural areas. Overall, interview and focus group informants did not elaborate on the subject of geography, suggesting that additional investigations of environment-related contributing factors may be needed.
In this case study we further considered differences between participating health regions that may impact the presence of certain pathogens. Although informants from semi-structured interviews did not directly address potential differences, observations made across all interviews and focus groups suggested that some dissimilarity exists. While the top pathogens identified (i.e. Salmonella, Campylobacter, E. coli, and Giardia) were similar, regional differences were identified and have been reported previously . For example, informants from health region B (urban) commonly identified S. Typhi as one of the most concerning pathogens to their region. The high number of S. Typhi cases observed in region B was attributed to the large South Asian immigrant population in their region. However, S. Typhi was not identified as one of the top important enteric pathogens by inspectors from the other participating health regions or in any of the focus group discussions, suggesting that the distribution of enteric pathogens does vary between regions, although the physical geography may not be the main reason for the observed differences.
Of the top pathogens identified in the case study, three (Salmonella, Campylobacter, and E. coli) were the same pathogens identified in a previous focus group study in Ontario . These pathogens are the top three leading causes of enteric illness reported in Ontario  and are among the top twelve most common domestically acquired enteric pathogens in Canada . The public health inspectors from region B that identified S. Typhi as an important pathogen associated it with travel, which is consistent with Canadian estimates that attributed 76% of S. Typhi cases to travel . The investigators from region B most often discussed the theme ‘access to healthcare’ and recognised the need for public resources in multiple languages. This need was also acknowledged in a previous study of public health investigators from Central West Ontario . Inspectors from other regions did not identify access to healthcare as an important contributing factor either, perhaps because they did not perceive it as an issue in their region. Under-reporting bias can skew perceptions of common factors that contribute to enteric illness so it is important to acknowledge existing barriers (e.g. language, geographic).
When considering pathogens of concern, informants from both semi-structured interviews and focus groups had varying interpretations of what importance meant to them. In general, informants defined importance as a term that encompassed disease severity and frequency. This may account for the discrepancy between the most important pathogens ranked in the case study and the most frequent pathogens ranked provincially and nationally. We also observed that informants from different public health fields considered different criteria when defining importance. A similar observation was made by Boxstael et al.  when they assessed perceptions of food safety issues amongst stakeholders from industry, government, consumer organizations, and universities.
During interviews, public health inspectors explained how infrastructure changes within health regions have been implemented to aid in the determination of the MLSI. Each region has up-to-date manuals, protocols, and pathogen specific standard questionnaires to assist in conducting case follow-up interviews. Investigators also commented that with more experience an investigator develops more confidence and skills to ask more probing questions and form hypotheses. This makes it easier to determine the MLSI. Nonetheless, determining the MLSI is still difficult. One public health investigator explained that while they listen to case stories and form their own probing questions based on responses, “it can be hard to speculate” about the MLSI in many cases. Another inspector noted that they are only able to solve about two out of ten outbreaks. This low solve rate is usually attributed to cases having difficulties recalling what they did or what they ate in weeks past.
When considering low solve rates, it is important to reflect on the complexities that exist between contributing factors. As previously identified, there are many factors, and attributing enteric illness to any one may be unrealistic and simplistic. Identifying and understanding these links and complex relationships can be critical for developing future preventative enteric illness measures. To mitigate this we should consider future changes in MLSI trends and the impact of complex risk factor relationships. However, many informants did not believe any changes would occur and assumed that population dynamics would not change in the future. It is unrealistic to assume that the Canadian population will remain static. Immigration and age trends suggest that in the next few years the median age of Canadians and the number of immigrants to Canada will both increase . Informants also did not consider the emergence of new pathogens or the influence of climate change. Projections suggest that under global warming, Canada will experience longer summers, milder winters, and more extreme precipitation. These climatic changes will affect the risk of enteric illness and subsequently alter disease rates . Informants may not have considered such factors since it can be hard to speculate whether these changes would occur, and subsequently, how they would affect disease incidence; especially if surveillance diagnostics change. One informant did however attribute disease prevalence with new food trends such as food smoking practices. Other informants suggested that the industry needs to implement regulations for such practices.
The case study generated valuable information for the prevention and management of enteric pathogens in Southern Ontario. However, due to the short duration and limited resources of the case study, it should be considered a pilot project. As the data were a product of an inclusive learning exercise that gave everyone the chance to facilitate the PE techniques learned, there were multiple participants collecting information which made data synthesis and analysis difficult. The data presented were also obtained from professional opinions and should therefore only be used as a supplement to existing and future surveillance data. Furthermore, as the focus groups consisted of PHAC and University of Guelph employees at different seniority and expertise levels, individuals may have withheld information if they felt inferior to their colleagues. It is also important to consider group versus one-on-one interview dynamics. The latter allows rapport to be established, where individuals feel more comfortable divulging information compared to group interviews. To overcome these challenges, future studies could conduct follow-up interviews, have informants participate in both an interview and a focus group, or ensure focus groups consist of informants with the same level and type of expertise. Other limitations include the underrepresentation of health regions. Due to limited time, only a small sample of informants was asked to volunteer from three select health regions. Future studies of enteric disease should include informants from local, provincial and federal public health, farmers, processing/packaging workers, retail workers, food safety authorities, scientists, and the general public. Capturing the perceptions of all stakeholders affected by aspects of enteric illness would ensure a more comprehensive analysis and understanding of the most likely source of infection for enteric pathogens across Southern Ontario.