André Ravel

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

SUMMARY 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.

). Food-specific attribution of selected gastrointestinal illnesses: Estimates from a Canadian expert elicitation survey

The study used a structured expert elicitation survey to derive estimates of food-specific attribution for nine illnesses caused by enteric pathogens in Canada. It was based on a similar survey conducted in the United States and focused on Campylobacter spp., Escherichia coli O157:H7, Listeria monocytogenes, nontyphoidal Salmonella enterica, Shigella spp., Vibrio spp., Yersinia enterocolitica, Cryptosporidium parvum, and Norwalk-like virus. A snowball approach was used to identify food safety experts within Canada. Survey respondents provided background information as well as self-assessments of their expertise for each pathogen and the 12 food categories. Depending on the pathogen, food source attribution estimates were based on responses from between 10 and 35 experts. For each pathogen, experts divided their estimates of total foodborne illness across 12 food categories and they provided a best estimate for each category as well as 5th and 95th percentile limits for foods considered to be vehicles. Their responses were treated as triangular probability distributions, and linear aggregation was used to combine the opinions of each group of experts for each pathogen-food source group. Across the 108 pathogen-food groups, a majority of experts agreed on 30 sources and 48 nonsources for illness. The number of food groups considered to be pathogen sources by a majority of experts varied by pathogen from a low of one food source for Vibrio spp. (seafood) and C. parvum (produce) to a high of seven food sources for Salmonella spp. Beta distributions were fitted to the aggregated opinions and were reasonable representations for most of the pathogen-food group attributions. These results will be used to quantitatively assess the burden of foodborne illness in Canada as well as to analyze the uncertainty in our estimates.

Seasonality in Human Salmonellosis: Assessment of Human Activities and Chicken Contamination as Driving Factors

This study used integrated surveillance data to assess the seasonality in retail chicken contamination and of human activities and their role on the seasonality of human endemic salmonellosis. From June 2005 to May 2008, reported cases of salmonellosis were followed-up comprehensively using a standardized questionnaire, and 616 retail chicken breasts were systematically tested for Salmonella, in one Canadian community. Poisson regression was used to model seasonality of human cases, Salmonella in retail chicken, and to assess the relationship between these and selected meteorological variables. The case-case approach was used to compare the activities of salmonellosis cases that occurred during the summer peak to the other cases. There were 216 human endemic salmonellosis cases (incidence rate: 14.7 cases/100,000 person-years), predominantly of Typhimurium and Enteritidis serotypes (28.4% and 20.8%, respectively). The monthly distribution of cases was associated with ambient temperature (p < 0.001) with a significant seasonal peak in June (p = 0.03) and July (p = 0.0005), but it was not associated with precipitation (p = 0.38). Several activities reported by cases tended to be more frequent during summer. Particularly, attending a barbeque and gardening within the 3 days before the disease onset were two significant risk factors for salmonellosis in June or July compared with the salmonellosis cases that occurred in the other months. Out of all chicken samples, 185 (30%) tested positive for Salmonella spp., Kentucky being the dominant serotype (44.3% of positive samples). The monthly proportion of positive chicken samples showed no seasonal variations (p = 0.30) and was not associated with the monthly count of human cases (p = 0.99). In conclusion, even though evidence generally supports chicken as a primary vehicle of Salmonella to humans, the contamination of retail chicken was not driving the seasonality in human salmonellosis. Attending a barbeque or gardening during the hotter months of the year should be further assessed for their risk.

Description and Burden of Travel‐Related Cases Caused by Enteropathogens Reported in a Canadian Community

BACKGROUND Risk of infections by enteropathogens among individuals traveling outside their country of residence is considered important. Such travel-related cases (TRC) have been poorly estimated and described in Canada. METHODS Data from an enhanced, passive surveillance system of diseases caused by enteropathogens within a Canadian community from June 2005 to May 2009 were used to describe TRC in terms of disease (pathogen, symptoms, hospitalization, duration, and timing of sickness relative to return); demographics (age and gender); and travel (destination, length, and accommodation); and to compare them with non-TRC. RESULTS Among 1,773 reported cases, 446 (25%) were classified as TRC with 9% of them being new immigrants. The main TRC diseases were campylobacteriosis, salmonellosis, and giardiasis. Disease onset occurred before return in 42% of TRC. Main destinations were Latin America/Caribbean and Asia. No differences by month and year were observed for onset, departure, and return dates. In addition to new immigrants, three subgroups of TRC based on travel destination, length of travel, type of accommodation, and age were identified and some diseases were more frequently observed in these subgroups. Generally, TRC did not differ from domestic cases in terms of age, gender, symptoms, hospitalization, and disease duration. Campylobacter coli and Salmonella enteritidis were significantly more frequent among TRC. CONCLUSIONS TRC of diseases caused by enteropathogens that are reportable in Canada represent a significant proportion of the burden of the total diseases. Subgroups of TRC exist and are associated with certain diseases. These results help inform the assessment of the actual risk related to travel for each subgroup of travelers and quantify the attribution of traveling abroad to the overall burden of these gastrointestinal diseases.

Environmental characteristics associated with campylobacteriosis: accounting for the effect of age and season.

Campylobacteriosis is a leading cause of acute bacterial gastroenteritis. An ecological study was undertaken to explore the association between environmental characteristics and incidence of campylobacteriosis in relation to four age groups and two seasonal periods. A multi-level Poisson regression model was used for modelling at the municipal level. High ruminant density was positively associated with incidence of campylobacteriosis, with a reduced effect as people become older. High poultry density and presence of a large poultry slaughterhouse were also associated with higher incidence, but only for people aged 16-34 years. The effect of ruminant density, poultry density, and slaughterhouses were constant across seasonal periods. Other associations were detected with population density and average daily precipitation. Close contacts with farm animals are probably involved in the associations observed. The specificity of age and season on this important disease must be considered in further studies and in the design of preventive measures.

Quantitative effect of refrigerated storage time on the enumeration of Campylobacter, Listeria, and Salmonella on artificially inoculated raw chicken meat.

Active monitoring of pathogens on retail foods has been recommended and implemented in a number of developed countries. Because only a portion of retail food is contaminated with pathogens, a cost-effective and informative surveillance program at the retail level often involves a two-stage approach of initial presence-absence analysis and subsequent pathogen enumeration in any positive samples. Most-probable-number (MPN) methods are more resource intensive and therefore used only for samples considered positive by presence-absence methods. Interpretation of the results assumes that the initial bacterial count remains relatively stable between the initiation of the presence-absence analysis and the enumeration analysis. The objective of this study was to quantify the influence of 4 degrees C storage for 5 and 8 days on pathogen counts on raw chicken. The three pathogens examined were Salmonella Typhimurium, Campylobacter jejuni, and Listeria monocytogenes. No significant differences were found between treatments for Salmonella and Campylobacter. However, significant differences were observed for Listeria; counts at day 0 were lower than counts after 5 or 8 days of refrigerated storage (the maximum mean difference was less than 0.6 log units). These findings suggest that a two-stage approach could overestimate the number of Listeria cells on chicken at the time of purchase. By using an MPN analysis on the presumptive positive samples after 5 days of refrigerated storage, this difference will be reduced. These findings support the decision to reduce surveillance costs by performing a two-stage analysis for Salmonella and Campylobacter on retail chicken. This study provides direction for future sampling or surveillance programs that include enumeration of Listeria on retail food.

Do patients with recurrent episodes of campylobacteriosis differ from those with a single disease event

BackgroundAlthough Campylobacter is the leading cause of reported bacterial gastro-enteritis in industrialized countries, little is known on its recurrence. The objective of this study is to describe the risk and the patient characteristics of recurrent episodes of human campylobacteriosis reported in Quebec.MethodsLaboratory-confirmed cases of campylobacteriosis reported in the province of Quebec, Canada, through ongoing surveillance between 1996 and 2006 were analyzed. The risk of having a recurrent episode of campylobacteriosis was described using life table estimates. Logistic regression was used to assess if gender, age and patient residential location were associated with an increased risk of recurrence.ResultsCompared to the baseline risk, the risk for a recurrent disease event was higher for a period of four years and followed a decreasing trend. This increased risk of a recurrent event was similar across gender, but higher for people from rural areas and lower for children under four years of age.ConclusionsThese results may suggest the absence of durable immunity or clinical resilience following a first episode of campylobacteriosis and periodical re-exposure, at least among cases reported through the surveillance system.

Influence of management, housing and personality of the stockperson on preweaning performances on independent and integrated swine farms in Québec

Abstract A cross-sectional study was implemented to determine which factors related to management, housing and stockperson in the farrowing quarters were associated with preweaning mortality and piglets weaned per litter in swine breeding herds. The associations were sought separately for the two most common types of swine production in Quebec. Forty-eight randomly-selected independent farms and 38 others belonging to integrated organizations specialized in swine production conveniently chosen among the largest organizations in Quebec participated in the study. Preweaning performances were computed from the sow records. Information on housing features was gathered during the visit to the farrowing quarters. Management practices were obtained through a questionnaire from the stockperson working in the farrowing quarters and his or her personality traits were evaluated through a personality test. Backward elimination procedure was used to build multiple linear regression models for each measure of performance for each type of farm. The procedures started from the management, housing and stockperson groups of variables taken separately and altogether, leading to the building of different regression models. Piglets weaned per litter averaged 8.9 and 8.6 on the independent and integrated farms, respectively and preweaning mortality, 14.4 and 15.4%, respectively. On the independent farms, high preweaning performances (high number of piglets weaned per litter and low preweaning mortality) were associated with routinely washing the farrowing crates, vaccination of the sows against neonatal diarrhea, farrowing crates equipped with high bottom bars, partially-slotted floors in the farrowing pens and high self-discipline from the stockperson. Poor performances were associated with the use of oxytocin around farrowing, mixed nursery-farrowing quarters and a stockperson being exaggeratedly self-assured and sensitive. On the integrated farms, the use of oxytocin at farrowing was also associated with poor performances, as well as several rooms or all-in/all-out farrowing quarters, farrowing crates equipped with high or medium bottom bars, totally-slotted floors and a stockperson being rather bold, suspecting and tense. High performances were positively associated with warmth, emotional stability and self-discipline from the stockperson. These findings provided evidences of the influence of the stockpersons personality on performances in particular, on the integrated farms on which the management in the farrowing quarters was more proactive (implying a stronger relationship between the stockperson and the pigs). In contrast, the importance to preweaning performances of general hygiene and health control was emphasized on the independent farms.

Factors associated with preventive behaviors regarding Lyme disease in Canada and Switzerland: a comparative study

BackgroundLyme disease (LD) is a vector-borne disease that is endemic in many temperate countries, including Switzerland, and is currently emerging in Canada. This study compares the importance of knowledge, exposure and risk perception for the adoption of individual preventive measures, within and between two different populations, one that has been living in a LD endemic region for several decades, the Neuchâtel canton in Switzerland, and another where the disease is currently emerging, the Montérégie region in the province of Québec, Canada.MethodsA web-based survey was carried out in both study regions (814 respondents) in 2012. Comparative analysis of the levels of adoption of individual preventive measures was performed and multivariable logistic regression analyses were used to test and compare how knowledge, exposure and risk perception were associated with the adoption of selected measures in both regions and globally.ResultsIn Montérégie, the proportion of reported adoption of five of the most commonly recommended preventive measures varied from 6% for ‘applying acaricides on one’s property’ to 49% for ‘wearing protective clothing’, and in Neuchâtel, proportions ranged from 6% (acaricides) to 77% for ‘checking for ticks (tick check)’. Differences were found within gender, age groups and exposure status in both regions. The perceived efficacy of a given measure was the strongest factor associated with the adoption of three specific preventive behaviors for both regions: tick check, protective clothing and tick repellent. Risk perception and a high level of knowledge about LD were also significantly associated with some of these specific behaviors, but varied by region.ConclusionsThese results strongly suggest that social and contextual factors such as the epidemiological status of a region are important considerations to take into account when designing effective prevention campaigns for Lyme disease. It furthermore underlines the importance for public health authorities to better understand and monitor these factors in targeted populations in order to be able to implement preventive programs that are well adapted to a population and the epidemiological contexts therein.

How to choose geographical units in ecological studies: Proposal and application to campylobacteriosis

In spatial epidemiology, the choice of an appropriate geographical unit of analysis is a key decision that will influence most aspects of the study. In this study, we proposed and applied a set of measurable criteria applicable for orienting the choice of geographical unit. Nine criteria were selected, covering many aspects such as biological relevance, communicability of results, ease of data access, distribution of exposure variables, cases and population, and shape of unit. These criteria were then applied to compare various geographical units derived from administrative, health services, and natural frameworks that could be used for the study of the spatial distribution of campylobacteriosis in the province of Quebec, Canada. In this study, municipality was the geographical unit that performed the best according to our assessment and given the specific objectives and time period of the study. Future research areas for optimizing the choice of geographical unit are discussed.