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Arsenault J.,University of Montreal | Berke O.,University of Guelph | Michel P.,Laboratoire Of Lutte Contre Les Zoonoses Dorigine Alimentaire | Ravel A.,Laboratoire Of Lutte Contre Les Zoonoses Dorigine Alimentaire | And 2 more authors.
BMC Infectious Diseases

Background: Campylobacter is a common cause of bacterial gastro-enteritis characterized by multiple environmental sources and transmission pathways. Ecological studies can be used to reveal important regional characteristics linked to campylobacteriosis risk, but their results can be influenced by the choice of geographical units of analysis. This study was undertaken to compare the associations between the incidence of campylobacteriosis in Quebec, Canada and various environmental characteristics using seven different sets of geographical units.Methods: For each set of geographical unit, a conditional autoregressive model was used to model the incidence of reported cases of campylobacteriosis according to environmental (poultry density, ruminant density, slaughterhouse presence, temperature, and precipitation) and demographic (population density, level of education) characteristics. Models were compared in terms of number of significant predictors, differences in direction and magnitude of predictors, and fit of the models.Results: In general, the number of significant predictors was reduced as the aggregation level increased. More aggregated scales tend to show larger but less precise estimates for all variables, with the exception of slaughterhouse presence. Regional characteristics associated with an increased regional risk of campylobacteriosis, for at least some geographical units, were high ruminant density, high poultry density, high population density, and presence of a large poultry slaughterhouse, whereas a reduction in risk was associated with a lower percentage of people with diplomas, a lower level of precipitation, and warmer temperature. Two clusters of elevated residual risk were observed, with different location and size depending on the geographical unit used.Conclusions: Overall, our results suggest that the use of municipality or census consolidated subdivision were the most optimal scales for studying environmental determinants of campylobacteriosis at a regional level. This study highlights the need for careful selection and analysis of geographical units when using ecological study designs. © 2012 Arsenault et al.; licensee BioMed Central Ltd. Source

Arsenault J.,University of Montreal | Michel P.,Laboratoire Of Lutte Contre Les Zoonoses Dorigine Alimentaire | Michel P.,University of Montreal | Berke O.,University of Guelph | And 4 more authors.
Spatial and Spatio-temporal Epidemiology

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. © 2013 The Authors. Source

Arsenault J.,University of Montreal | Michel P.,University of Montreal | Michel P.,Laboratoire Of Lutte Contre Les Zoonoses Dorigine Alimentaire | Berke O.,University of Guelph | And 5 more authors.
Epidemiology and Infection

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. © 2011 Cambridge University Press. Source

Berthiaume P.,Laboratoire Of Lutte Contre Les Zoonoses Dorigine Alimentaire | Berthiaume P.,University of Montreal | Ravel A.,Laboratoire Of Lutte Contre Les Zoonoses Dorigine Alimentaire | Ravel A.,University of Montreal | And 5 more authors.
Biosystems Engineering

Two Agroenvironmental hygienic pressure indicators (AHPIs) were developed to evaluate the effects of livestock production on water contamination and the risk for human health by expressing a complex public health risk via simple quantifiable figures. The first of the two AHPIs is addressing the aspect of surface water contamination while the second one is dealing with groundwater contamination. Each of the two AHPIs is built from a multiplicative model based on 25 parameters related to the transmission of bacteria through excretion by animals, survival in manure, and by run-off or infiltration water produced by rainfall. A global sensitivity approach was used to identify the most significant parameters in regard to the AHPIs output results. This analysis found that bacterial survival on the soil after manure spreading or grazing of animals (Ks), the proportion of bacteria able to reach surface water with run-off from manure on the soil (Brun-off), bacteria concentration in faeces Bconc, within-herd proportion of animals shedding the pathogenic bacteria targeted (Bprev) and the area used for pasture (A) - on bovine farms - are the most influential parameters with respect to the estimation of the AHPIs. With the exception of the latter element, these factors are all directly related to bacterial characteristics and parameters for which obtaining high quality data is most challenging. The identification of these most influential parameters will guide further research to enhance both the precision application of the AHPIs, and their use in managing public health risks. Crown Copyright © 2009. Source

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