Verotoxigenic Escherichia coli: costs of illness in Canada, including long-term health outcomes.

The main objective of this study was to provide cost estimates of human Escherichia coli O157 infection to facilitate future assessment of the benefits and costs of alternative preventive strategies to reduce illness. We investigated the costs of illness to Canadians from primary human infection by verotoxigenic E. coli O157 (also called Shiga toxin-producing E. coli O157) using data from the National Notifiable Diseases Registry. We used relative risk information from peer-reviewed publications to estimate the burden of illness and associated costs for eight long-term health outcomes. National estimates of the number of cases (mean and 5th and 95th percentiles), associated costs, and a rank correlation test to identify which outcomes were associated with the highest per capita costs were calculated. An estimated 22,344 cases of primary infections occur in Canada annually, costing $26.7 million. There are 37,867 additional on-going long-term health outcomes costing $377.2 million each year. Our analysis indicated that the annual cost for primary and long-term illness is $403.9 million. The analysis supports evaluation of alternative control and prevention measures and the development and implementation of policy and practices aimed at safe food production.

Respiratory symptoms and the case definition of gastroenteritis: an international analysis of the potential impact on burden estimates.

Estimates of the burden of foodborne disease rely on attributing a proportion of syndromic gastroenteritis to foodborne transmission. Persons with syndromic diarrhoea/vomiting can also present with concurrent respiratory symptoms that could be due to respiratory infections, gastrointestinal infections, or both. This distinction is important when estimating the foodborne disease burden but has rarely been considered. Using data from population surveys from Australia, Canada and the USA we describe the effect of excluding persons with respiratory and associated symptoms from the case definition of gastroenteritis. Excluding persons first with respiratory symptoms, or second with respiratory symptoms plus fever and headache, resulted in a decrease in the weighted estimates of acute gastroenteritis of about 10-50% depending on the exclusion criteria. This has the potential to have a very significant impact on estimates of the burden of foodborne infections using syndromic case definitions of acute gastroenteritis.

Burden of acute gastrointestinal illness in Canada, 1999-2007: interim summary of NSAGI activities.

INTRODUCTION: The National Studies on Acute Gastrointestinal Illness (NSAGI) initiative was designed to generate baseline period prevalence rates of self-reported AGI in communities across Canada, assess the burden associated with AGI, and quantify the under-reporting of AGI in Canada's national enteric disease reporting systems. METHODS: Methods utilized included population surveys administered randomly via telephone services. Three population surveys in three locations within Canada included over 10,000 residents. Questions pertained to recent symptoms as well as socio-demographic factors, use of the health care system and missed work or school due to illness. RESULTS: In summary of published results, there are an estimated 1.3 episodes of AGI per person-year and an estimated 10-47, 13-37 and 23-49 cases in the community for every case of verotoxigenic Escherichia coli, Salmonella and Campylobacter, respectively, captured within the national surveillance system. AGI represents an annual per capita cost of $115 CAD. DISCUSSION: The work of NSAGI highlights the significant burden and impact of AGI in the Canadian population. These results will also be incorporated into the current work at the World Health Organization (WHO) to estimate the global burden of food related illnesses.

Estimation of the costs of acute gastrointestinal illness in British Columbia, Canada.

The costs associated with gastrointestinal infection (GI) in the province of British Columbia, Canada, were estimated using data from a population-based survey in three health service delivery areas, namely Vancouver, East Kootenay and Northern Interior. The number of cases of disease, consequent expenditure of resources and associated economic costs were modeled as probability distributions in a stochastic model. Using 2004 prices, the estimated mean annual cost per capita of gastrointestinal infection was CAN$128.61 (207.96 euros), with a mean annual cost per case of CAN$1,342.57 (2,170.99 euros). The mean estimate of the overall economic burden to British Columbia was CAN$514.2 million (831.5 million euros) (95% CFI CAN$161.0 million to CAN$5.8 billion; 260.3 million euros to 9.38 billion euros). The major element of this cost was the loss of productivity associated with time away from paid employment by both the sick and their caregivers. Sensitivity analysis suggested that the uncertainty associated with the base model assumptions did not significantly affect the estimates. The results are comparable to those obtained in an earlier study using a similar analytical framework and data from the city of Hamilton, Ontario, Canada.

Under-reporting of infectious gastrointestinal illness in British Columbia, Canada: who is counted in provincial communicable disease statistics?

Under-reporting of infectious gastrointestinal illness (IGI) in British Columbia, Canada was calculated using simulation modelling, accounting for the uncertainty and variability of input parameters. Factors affecting under-reporting were assessed during a cross-sectional randomized telephone survey. For every case of IGI reported to the province, a mean of 347 community cases occurred (5th and 95th percentile estimates ranged from 181 to 611 community cases, respectively). Vomiting [odds ratio (OR) 2.15, 95% confidence interval (CI) 1.03-4.49] and antibiotic use in the previous 28 days (OR 3.59, 95% CI 1.17-10.97) significantly predicted health-care visits in a logistic regression model. In bivariate analyses, physicians were significantly less likely to request stool samples from patients with vomiting (RR 0.09, 95% CI 0.01-0.65) and patients of North American as opposed to non-North American cultural groups (RR 0.38, 95% CI 0.15-0.96). Physicians were more likely to request stool samples from older patients (P=0.003), patients with fewer household members (P=0.002) and those who reported anti-diarrhoeal use following illness (RR 3.33, 95% CI 1.32-8.45). People with symptoms of vomiting were under-represented in provincial communicable disease statistics. Differential degrees of under-reporting must be understood before biased surveillance data can be adjusted.

A common, symptom-based case definition for gastroenteritis.

National studies determining the burden of gastroenteritis have defined gastroenteritis by its clinical picture, using symptoms to classify cases and non-cases. The use of different case definitions has complicated inter-country comparisons. We selected four case definitions from the literature, applied these to population data from Australia, Canada, Ireland, Malta and the United States, and evaluated how the epidemiology of illness varied. Based on the results, we developed a standard case definition. The choice of case definition impacted on the observed incidence of gastroenteritis, with a 1.5-2.1 times difference between definitions in a given country. The proportion of cases with bloody diarrhoea, fever, and the proportion who sought medical care and submitted a stool sample also varied. The mean age of cases varied by <5 years under the four definitions. To ensure comparability of results between studies, we recommend a standard symptom-based case definition, and minimum set of results to be reported.

Burden and cost of gastroenteritis in a Canadian community.

This study estimated the health burden and costs associated with gastroenteritis in the City of Hamilton (Ontario, Canada). The number of cases, number of different resource units used, and cost per resource unit were represented by probability distributions and point estimates. These were subsequently integrated in a stochastic model to estimate the overall burden and cost in the population and to depict the uncertainty of the estimates. The estimated mean annual cost per capita was Can dollar 115. The estimated mean annual cost per case was Can dollar 1,089 and was similar to other published figures. Gastroenteritis represented a significant burden in the study population, with costs high enough to justify prevention efforts. These results, currently the most accurate available estimates for a Canadian population, can inform future economic evaluations to determine the most cost effective measures for reducing the burden and cost of gastroenteritis in the community.

Magnitude and distribution of acute, self-reported gastrointestinal illness in a Canadian community.

To estimate the magnitude and distribution of self-reported, acute gastrointestinal illness in a Canadian-based population, we conducted a retrospective, cross-sectional telephone survey of approximately 3500 randomly selected residents of the city of Hamilton (Ontario, Canada) from February 2001 to February 2002. The observed monthly prevalence was 10% (95 % CI 9.94-10.14) and the incidence rate was 1.3 (95 % CI 1.1-1.4) episodes per person-year; this is within the range of estimates from other developed countries. The prevalence was higher in females and in those aged < 10 years and 20-24 years. Overall, prevalence peaked in April and October, but a different temporal distribution was observed for those aged < 10 years. Although these data were derived from one community, they demonstrate that the epidemiology of acute gastrointestinal illness in a Canadian-based population is similar to that reported for other developed countries.

The study of infectious intestinal disease in England: socio-economic impact.

To assess the socio-economic impact of infectious intestinal disease (IID) on the health care sector, cases and their families, cases of IID ascertained from a population cohort component and those presenting to general practices were sent a socio-economic questionnaire 3 weeks after the acute episode. The impact of the illness was measured and the resources used were identified and costed. The duration, severity and costs of illness linked to viruses were less than those linked to bacteria. The average cost per case of IID presenting to the GP was Pound Sterling253 and the costs of those not seeing a GP were Pound Sterling34. The average cost per case was Pound Sterling606 for a case with salmonella, Pound Sterling315 for campylobacter, Pound Sterling164 for rotavirus and Pound Sterling176 for SRSV. The estimated cost of IID in England was Pound Sterling743m expressed in 1994/5 prices. The costs of IID are considerable and the duration of the illness was found to be longer than previous reports have suggested.

Characterization of Salmonella associated with pig ear dog treats in Canada.

In the summer of 1999, the incidence of Salmonella enterica serotype Infantis infections in Alberta rose dramatically. Subsequent laboratory and epidemiological investigations established that an outbreak of human disease caused by this organism was occurring across Canada and was associated with pet treats for dogs produced from processed pig ears. Laboratory investigations using phage typing and pulsed-field gel electrophoresis (PFGE) established that isolates of Salmonella serotype Infantis from pig ear pet treats and humans exposed to pig ear pet treats comprised a well-defined subset of all isolates analyzed. Of the 53 subtypes of Salmonella serotype Infantis obtained around the time of the outbreak as defined by PFGE and phage typing, only 6 subtypes were associated with both human infection and isolation from pig ears. Together with information from epidemiological studies, these investigations established pig ear pet treats as the cause of the Salmonella serotype Infantis outbreak. The results are consistent with a model in which contaminated pig ear pet treats constitute a long-term, continuing vehicle for infection of the human population rather than causing temporally delimited point-source outbreaks. During the course of this outbreak, several other Salmonella serotypes were also isolated from pet treats, suggesting these products may be an important source of enteric infection in both humans and dogs. Though isolates of Salmonella serotypes other than Salmonella serotype Infantis from pet treats were also subjected to PFGE and phage typing, no link with human disease could be definitively established, and the contribution of pig ear pet treats to human disease remains unclear. Elimination of bacterial contamination from pet treats is required to reduce the risk of infection from these products.

Enteric and foodborne disease in children: A review of the influence of food- and environment-related risk factors.

Canadian statistics show that children from birth to four years of age are more likely to be reported with an infection from Campylobacter, Giardia, Salmonella and Shigella species, and verotoxigenic Escherichia coli than any other age group. A review of the Canadian and international literature, and an analysis of case and outbreak data suggest that the risk factors for infection in young children (ages birth to four years) are different from the risk factors for older children and adults. In children from birth to four years of age, infant formula, fast foods, snacks and candies have caused major outbreaks of enteric and foodborne diseases; however, the contamination of a child's environment or the presence of ill individuals in a household may be highly significant to disease expression. Contact with animals (including family pets) and contaminated surfaces, together with experimental touching and testing behaviours, are important routes of infection for infants and preschool children. Risk factors for enteric infections in children appear to be related, occasionally, to specific foods that are particularly attractive to all children (all age groups from infants up to and including elementary school-aged childen), to an infected person or pet in the same household, or to the contamination of a child's environment. Nonfood-related risk factors may be of particular significance in infection in infants and very young children. Contact with animals, particularly exotic pets and farm animals, or their environments should be considered to be a potential source of infection in children in situations in which there is an absence of other risk factors. The evidence presented in the current paper emphasizes the importance of personal and home hygiene practices in limiting children's exposure to enteric pathogens. Strict hand washing practices and restrictions on touching birds, reptiles and other animals at petting zoos or in nursery and primary school facilities are recommended to avoid widespread infection. Public health authorities should consider the development of guidelines on the provision of hand washing facilities and instruction notices in settings where the public may come into contact with farm or other animals in jurisdictions where such guidelines do not already exist.

A study of infectious intestinal disease in England: plan and methods of data collection.

The Committee on the Microbiological Safety of Food, set up in 1989 by the Department of Health in response to national epidemics of foodborne infection, considered the available evidence and commissioned a study of infectious intestinal disease (IID) in England. Seventy practices (with 489,500) patients overall) recruited from the Medical Research Council's General Practice Research Framework between August 1993 and January 1995 collected data for one year. The practice populations were representative of practices in England by area and urban/rural location, but with fewer small and affluent practices. There were five main components. i) A population cohort of 9776 (40% of those eligible) were enrolled to estimate the incidence and aetiology of IID in the community, and a large proportion were followed up. A median of 10% of patients on practice age-sex registers had moved away or died. ii) A nested case control component based on cases ascertained in the cohort was used to identify risk factors for IID in the community. iii) In a case control component used to identify risk factors and to estimate the incidence and aetiology of IID presenting in 34 general practices 70% of the 4026 cases returned risk factor questionnaires, 75% submitted stools, and matched controls were found for 75% of cases. iv) An enumeration component was used to estimate the incidence of IID presenting to general practitioners (GPs) in 36 practices and the proportion of specimens sent routinely for microbiological examination. v) In a socioeconomic costs component used to estimate the burden of illness of IID in the community and presenting to GPs 63% of those who returned a risk factor questionnaire also returned a socioeconomic questionnaire and were representative by age, sex, and social class. Despite variable enrolment and compliance the study sample had sufficient power for the multivariable analysis. The characteristics associated with low enrollment and compliance must be considered in the interpretation of the main study results.