Paul Sockett

Estimating the Burden of Acute Gastroenteritis, Foodborne Disease, and Pathogens Commonly Transmitted by Food: An International Review

The burden of foodborne disease is not well defined in many countries or regions or on a global level. The World Health Organization (WHO), in conjunction with other national public health agencies, is coordinating a number of international activities designed to assist countries in the strengthening of disease surveillance and to determine the burden of acute gastroenteritis. These data can then be used to estimate the following situations: (1) the burden associated with acute gastroenteritis of foodborne origin, (2) the burden caused by specific pathogens commonly transmitted by food, and (3) the burden caused by specific foods or food groups. Many of the scientists collaborating with the WHO on these activities have been involved in quantifying the burden of acute gastroenteritis on a national basis. This article reviews these key national studies and the international efforts that are providing the necessary information and technical resources to derive national, regional, and global burden of disease estimates.

Estimated numbers of community cases of illness due to Salmonella, Campylobacter and verotoxigenic Escherichia coli: Pathogen-specific community rates

OBJECTIVE To estimate the annual number of cases of illness due to verotoxigenic Escherichia coli (VTEC), Salmonella and Campylobacter in the Canadian population, using data from the National Notifiable Disease registry (NND), estimates of under-reporting derived from several National Studies on Acute Gastrointestinal Illness, and the literature. METHODS For each of the three pathogens (VTEC, Salmonella and Campylobacter), data were used to estimate the percentage of cases reported at each step in the surveillance system. The number of reported cases in the NND for each pathogen was then divided by these percentages. In cases where the pathogen-specific estimates were unavailable, data on acute gastrointestinal illness were used, accounting for differences between those with bloody and nonbloody diarrhea. RESULTS For every case of VTEC, Salmonella and Campylobacter infection reported in the NND, there were an estimated 10 to 47, 13 to 37, and 23 to 49 cases annually in the Canadian population, respectively. CONCLUSIONS The authors estimate that a significant number of infections due to VTEC, Salmonella and Campylobacter occur each year in Canada, highlighting the fact that these enteric pathogens still pose a significant health burden. Recognizing the significant amount of under-reporting is essential to designing appropriate interventions and assessing the impact of these pathogens in the population.

Characterization of Salmonella Associated with Pig Ear Dog Treats in Canada

ABSTRACT 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 ofSalmonella 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 theSalmonella 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 otherSalmonella 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 ofSalmonella serotypes other thanSalmonella 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.

West Nile Virus Surveillance and Diagnostic: A Canadian Perspective

A surveillance program has been in place since 2000 to detect the presence of West Nile virus (WNV) in Canada. Serological assays are most appropriate when monitoring for human disease and undertaking case investigations. Genomic amplification procedures are more commonly used for testing animal and mosquito specimens collected as part of ongoing surveillance efforts. The incursion of WNV into this country was documented for the first time in 2001 when WNV was demonstrated in 12 Ontario health units during the late summer and fall. In 2002 WNV activity was documented by avian surveillance in Ontario by mid-May with subsequent expansion of the virus throughout Ontario and into Quebec, Manitoba, Saskatchewan and Nova Scotia. Human cases were recorded in both Ontario and Quebec in 2002 with approximately 800 to 1000 probable, confirmed and suspect cases detected. The possible recurrence and further spread of WNV to other parts of Canada in 2003 must be anticipated with potential risk to public health. The continued surveillance and monitoring for WNV-associated human illness is necessary and appropriate disease prevention measures need to be in place in 2003.

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 GIS-driven integrated real-time surveillance pilot system for national West Nile virus dead bird surveillance in Canada

BackgroundAn extensive West Nile virus surveillance program of dead birds, mosquitoes, horses, and human infection has been launched as a result of West Nile virus first being reported in Canada in 2001. Some desktop and web GIS have been applied to West Nile virus dead bird surveillance. There have been urgent needs for a comprehensive GIS services and real-time surveillance.ResultsA pilot system was developed to integrate real-time surveillance, real-time GIS, and Open GIS technology in order to enhance West Nile virus dead bird surveillance in Canada.Driven and linked by the newly developed real-time web GIS technology, this integrated real-time surveillance system includes conventional real-time web-based surveillance components, integrated real-time GIS components, and integrated Open GIS components. The pilot system identified the major GIS functions and capacities that may be important to public health surveillance. The six web GIS clients provide a wide range of GIS tools for public health surveillance. The pilot system has been serving Canadian national West Nile virus dead bird surveillance since 2005 and is adaptable to serve other disease surveillance.ConclusionThis pilot system has streamlined, enriched and enhanced national West Nile virus dead bird surveillance in Canada, improved productivity, and reduced operation cost. Its real-time GIS technology, static map technology, WMS integration, and its integration with non-GIS real-time surveillance system made this pilot system unique in surveillance and public health GIS.

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.

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.

Communicable Disease Surveillance: Notification of Infectious Diseases in Canada

Canada, like many countries. collects and collates aggregate data on communicable diseases nationally. The main objectives of this system are to provide a mechanism for monitoring the health of the population by identifying and responding to changes in reporti ng trends of specific diseases and to provide information that can contribute to the development of health policy and the planning of care, prevention and control programs. These activities function at local, provincial/territorial , and national government levels , focusing on populations rather than individuals. Specific use of national surveillance data includes the identification and control of disease outbreaks; the development and implementation of population-based prevention and control activities and the monitoring of these activities; the production of statistics to aid priority setting; and contributions to international surveil lance activities (I). This paper briefly describes the system by which information on notifiable diseases is collected and collated by the federal government. Information on selected (notifiable) communicable diseases has been collected by the Canadian government since 1924. The Statistics Canada and the Health Canada Acts contain the federal governments mandate to collect these data (2,3) . However, provincial governments enact legislation designed to capture individual reports of cases. The list of diseases for which aggregated nationa l data is collected is subject to change, through recategorization of diseases or enlargement by the addition of new diseases to the list. At present 4 7 diseases are reported to the Bureau of Infectious Diseases, Laboratory Centre for Disease Control (LCDC) in Ottawa (Table 1). A subcommittee convened in 1987 by the national Advisory Committee on Epidemiology (ACE) defined the current list. The list was amended to include hepatitis C in 1991 and a more extensive breakdown of syphilis in 1992.