Pascal Michel

Associations between Indicators of Livestock Farming Intensity and Incidence of Human Shiga Toxin-Producing Escherichia Coli Infection

The impact of livestock farming on the incidence of human Shiga toxin-producing Escherichia coli (STEC) infection was assessed by using several livestock density indicators (LDI) that were generated in a systematic approach. A total of 80 LDI were considered suitable proxy measures for livestock density. Multivariate Poisson regression identified several LDI as having a significant spatial association with the incidence of human STEC infection. The strongest associations with human STEC infection were the ratio of beef cattle number to human population and the application of manure to the surface of agricultural land by a solid spreader and by a liquid spreader showed. This study demonstrates the value of using a systematic approach in identifying LDI and other spatial predictors of disease.

Epidemiology of Crohn's disease in Québec, Canada.

Background: Crohns disease (CD) is an idiopathic inflammatory bowel disease (IBD). We aimed to determine the prevalence and incidence of CD in Québec and characterize the demographic and health‐related factors associated with this disease. Methods: We identified CD cases in the provincial administrative databases for the years 1993–2002. The CD prevalence and incidence rates were estimated respectively for the periods 1993–2002 and 1998–2000. We validated the identified cases using clinically confirmed IBD cases. Predictor variables of CD were analyzed using the Poisson regression model to explain the variation in CD incidence rates across Québec. Results: In all, 21,172 patients fulfilled the CD case definition for the period. The age and sex standardized average prevalence rate for 1993–2002 was 189.7 cases / 100,000 population and the age and sex standardized incidence rate of CD for the 1998–2000 period was 20.2 cases / 100,000 person‐years. The female/male cases ratio among incident cases was 0.74 for the 0–14‐year‐old group, 1.30 for the 15–64‐year‐old group, and 1.77 for the cases older than 65 years old. After adjustment, independent predictors of CD incidence were: incidence of 5 reportable enteric diseases, proportion of individuals of Jewish ethnicity, and proportion of immigrant people. Conclusions: The identified predictors of CD explained 20% of the regional variance in the incidence rate of CD in the Québec population. Other factors such as genetic susceptibility to CD or the effect of an environmental cause should be taken into consideration in the models to explain the residual variance.

Geographical and temporal distribution of human giardiasis in Ontario, Canada.

BackgroundGiardia is the most frequently identified intestinal parasite in North America. Although information on geographical distribution of giardiasis is critical in identifying communities at high risk, little has been done in this area. Therefore, the objective of this study was to investigate the geographical and temporal distribution of human giardiasis in Ontario in order to identify possible high risk areas and seasons. Two spatial scales of analyses and two disease measures were used with a view to identifying the best of each in assessing geographical patterns of giardiasis in Ontario. Global Morans I and Moran Local Indicators of Spatial Associations were used to test for evidence of global and local spatial clustering, respectively.ResultsThere were seasonal patterns with summer peaks and a significant (P < 0.001) decreasing temporal trend. Significant (P < 0.05) global spatial clustering of high rates was observed at the Census Sub-division spatial scale but not at the Census Division scale. The Census Sub-division scale was a better scale of analyses but required spatial empirical Bayesian smoothing of the rates. A number of areas with significant local clustering of giardiasis rates were identified.ConclusionsThe study identified spatial and temporal patterns in giardiasis distribution. This information is important in guiding decisions on disease control strategies. The study also showed that there is benefit in performing spatial analyses at more than one spatial scale to assess geographical patterns in disease distribution and that smoothing of disease rates for mapping in small areas enhances visualization of spatial patterns.

Risk factors for Salmonella typhimurium DT104 and non-DT104 infection: a Canadian multi-provincial case-control study.

To identify risk factors for sporadic Salmonella Typhimurium definitive phage-type 104 (DT104) and non-DT104 diarrhoeal illness in Canada, we conducted a matched case-control study between 1999 and 2000. Cases were matched 1:1 on age and province of residence. Multivariate analysis suggested that recent antibiotic use [odds ratio (OR) 5.2, 95% confidence interval (CI) 1.8-15.3], living on a livestock farm (OR 4.9, 95% CI 1.9-18.9), and recent travel outside Canada (OR 4.1, 95% CI 1.2-13.8) are independent risk factors for DT104 illness. Similar analyses suggested that recent travel outside North America is a sizable risk factor for non-DT104 illness (OR 66.8, 95% CI 6.7-665.3). No food exposure was a risk factor in either analysis. Educating health-care providers and the public about appropriate antibiotic use and antimicrobial resistance is important. Appropriate administration of antibiotics to livestock, particularly cattle, and hygienic measures such as handwashing after contact with farm animals may reduce risk. Travel represents an important and probably underestimated risk factor for sporadic illness with S. Typhimurium. Improved national surveillance and detailed investigation of travel-related illness are required.

The use of outbreak information in the interpretation of clustering of reported cases of Escherichia coli O157 in space and time in Alberta, Canada, 2000-2002

We obtained a list of all reported cases of Escherichia coli O157 in Alberta during the 2000-2002 period, and using scan statistics we identified yearly temporal and spatial clusters of reported cases of E. coli O157 during the summer and in southern Alberta. However, the location of the spatial cluster in the south was variable among years. The impact of using both outbreak and sporadic data or only sporadic data on the identification of spatial and temporal clusters was small when analysing individual years, but the difference between spatial clusters was pronounced when scanning the entire study period. We also identified space-time clusters that incorporated known outbreaks, and clusters that were suggestive of undetected outbreaks that we attempted to validate with molecular data. Our results suggest that scan statistics, based on a space-time permutation model, may have a role in outbreak investigation and surveillance programmes by identifying previously undetected outbreaks.

Determinants of the geographical distribution of endemic giardiasis in Ontario, Canada: a spatial modelling approach

Giardiasis surveillance data as well as drinking water, socioeconomic and land-use data were used in spatial regression models to investigate determinants of the geographic distribution of endemic giardiasis in southern Ontario. Higher giardiasis rates were observed in areas using surface water [rate ratio (RR) 2.36, 95 % CI 1.38-4.05] and in rural areas (RR 1.79, 95 % CI 1.32-2.37). Lower rates were observed in areas using filtered water (RR 0.55, 95 % CI 0.42-0.94) and in those with high median income (RR 0.62, 95 % CI 0.42-0.92). Chlorination of drinking water, cattle density and intensity of manure application on farmland were not significant determinants. The study shows that waterborne transmission plays an important role in giardiasis distribution in southern Ontario and that well-collected routine surveillance data could be useful for investigation of disease determinants and identification of high-risk communities. This information is useful in guiding decisions on control strategies.

Estimation of the under-reporting rate for the surveillance of Escherichia coli O157:H7 cases in Ontario, Canada.

Two models estimating the proportion of Escherichia coli O157:H7 cases not reported in the Ontario notifiable diseases surveillance system are described. The first model is a linear series of adjustments in which the total number of reported cases is corrected by successive underreporting coefficients. The structure of the second model is based on a relative difference in the proportion of E. coli O157:H7 cases which are hospitalized between the surveillance database and the underlying population. Based on this analysis, the rate of under-reporting of symptomatic cases of E. coli O157:H7 infection in Ontario ranges from 78 to 88% corresponding to a ratio of 1 reported case for approximately 4-8 symptomatic cases missed by the surveillance system. This study highlights the need to increase awareness among public health workers of the potential biases that may exist in the interpretation of routine surveillance data.

Syndromic Surveillance of Norovirus Using over the Counter Sales of Medications related to Gastrointestinal Illness

OBJECTIVE To assess whether over-the-counter (OTC) sales of gastrointestinal illness (GI)-related medications are associated with temporal trends of reportable community viral, bacterial and parasitic infections. METHODS The temporal patterns in weekly and seasonal sales of nonprescription products related to GI were compared with those of reportable viral, bacterial and parasitic infections in a Canadian province. RESULTS Temporal patterns of OTC product sales and Norovirus activity were similar, both having highest activity in the winter months. In contrast, GI cases from both bacterial and parasitic agents were highest from late spring through to early fall. CONCLUSIONS Nonprescription sales of antidiarrheal and antinauseant products are a good predictor of community Norovirus activity. Syndromic surveillance through monitoring of OTC product sales could be useful as an early indicator of the Norovirus season, allowing for appropriate interventions to reduce the number of infections.

Age-Specific Frequencies of Antibodies to Escherichia coli Verocytotoxins (Shiga Toxins) 1 and 2 among Urban and Rural Populations in Southern Ontario

In 173 urban residents and 232 rural dairy-farm residents (age range, 0-70 years) who were stratified for age, the frequency of antiverocytotoxin 2 antibodies (VT2 Abs) (frequency in urban residents, 46%; frequency in rural residents, 65%) was significantly higher than that of antiverocytotoxin 1 antibodies (VT1 Abs) (frequency in urban residents, 12%; frequency in rural residents, 39%) (P< or =.001). The frequency of VT2 Abs (93%) was also significantly higher than that of VT1 Abs (50%) in 14 patients with hemolytic uremic syndrome (HUS) associated with verocytotoxin-producing Escherichia coli (VTEC) strains that expressed both toxins. In urban residents, the frequency of both antibodies tended to decrease between the first and the second decades of life, and it then increased until the fifth decade of life, before, in the case of VT2 Abs, decreasing again. This pattern, which inversely reflects the age-related incidence of HUS, is consistent with a role for antiverocytotoxin antibodies in protective immunity. In dairy-farm residents, peak frequencies of antibodies to both toxins occurred during the first decade of life and remained elevated for 3 decades before decreasing, a pattern consistent with frequent exposure to bovine VTEC from an early age.

A National Epidemic of Campylobacteriosis in Iceland, Lessons Learned

Epidemics often result in organizational, policy and technical changes within a country. In 1999, an epidemic of campylobacteriosis was reported in Iceland. The recent availability of fresh poultry products in the marketplace was suggested as the source of infection. This paper reports on the context of the epidemic, reviews interventions implemented to prevent campylobacteriosis, and discusses lessons learned. A retrospective study of interventions implemented in Iceland from June 1995 to December 2007 was conducted by interviewing key informants and reviewing Iceland’s literature. Cumulative incidence rates of domestic campylobacteriosis by year and average incidence rates per epidemic period were calculated. Interventions included on‐farm surveillance of Campylobacter, producer education, enhanced biosecurity measures, changes in poultry processing, a leak‐proof packaging policy, a freezing policy for products from Campylobacter‐positive poultry flocks, consumer education, and the creation of a legislated inter‐organizational response committee. These interventions appear to have collectively contributed to a decrease in campylobacteriosis’ incidence rate near pre‐epidemic baseline levels. Expert consultations revealed that the implementation of a Campylobacter surveillance program in poultry and the freezing policy were critical to controlling the disease in the Icelandic population. It was also recognized that new multidisciplinary collaborations among public health, veterinary, and food safety authorities and a sustained co‐operation from the poultry industry were integral factors to the mitigation of the epidemic. Iceland’s response to the campylobacteriosis epidemic is a lesson learned of inter‐disciplinary and inter‐organizational precautionary public health action in the face of a complex public health issue.