Foodborne Disease in Canada - a 5-year Summary

Abstract

Five years of foodbome disease surveillance in Canada were examined. Microorganisms, particularly Salmonella spp., Staphylococcus aureus and Clostridium perfringens, were the main etiologic agents, but diseases also resulted from contamina-nation of food with chemicals and parasites or food containing naturally-occurring plant and animal toxins. The foods involved were, in general, potentially hazardous items, such as meat and poultry. Where information is known, most of the problems associated with foodbome illness occurred at foodservice establishments , but the impact of mishandling in homes and food processing establishments was also great. The kinds of data accumulated were similar to those from the United States for the same time period, In order to reduce the prevalence of foodbome disease, specific educational and enforcement programs have to be initiated. Similar approaches could be taken for both countries. A national foodborne disease reporting system was established in Canada in 1973 and detailed data on such disease have been collected, collated and published from 1973 to 1977 (4). These data, updated where new facts were available, were used to prepare this 5-year summary. The method of collecting information and the definitions of terms used have been published previously (5). The purpose of such a summary is to compare information for each of the years and to observe trends so that better control measures can be instituted. It is recognized, however, that reported data are limited and actual numbers of persons ill from foodborne disease are far greater than is apparent in this summary. Hauschild and Bryan (3) estimated that between 150,000 and 300,000 foodborne and waterborne cases occurred annually in 1974 and in 1975 in Canada. These figures are between 20 and 70 times higher than the cases reported for those years. The numbers of outbreaks, single cases and total cases showed the same trend, i.e., a slight increase from 1973 to J 974, a dramatic rise in 1975 with a peak in that year or 1976, and then a slight decrease in 1977 (Table 1, Fig. 1). Total incidents and cases for the United States also rose in 1975 and then declined whereas those of known etiol-ogy for both countries showed less fluctuation over the years. Microbiological agents were the main one~ respons:-bie. and where some information was available on tnose incidents of unknown etiology to indicate probable agents, microbiological ones were predominant. Agents responsible for illness are listed in Table 2. Staphylococcus aureus and Salmonella spp. were the main microorganisms causing food poisoning. At the end of the 5-year period, there was a trend toward fewer incidents of staphylococcal intoxication and more of salmonellosis. The two serotypes that caused incidents most frequently were Salmonella typhimurium and Saltiwnella enteritidis (Table 3). The number of incidents involving these two strains increased steadily from 1973 to 1977 (S. typhimurium from 4 to 13, S. enteritidis from 2 to 5). The ranking of the ten most frequent serotypes causing foodborne salmonellosis in Canada closely resembled that in the United States (Table 3). Clos-tridium perfringens was the third most important agent in the number of incidents reported and second in the number of cases. This organism also caused the highest case-to-outbreak ratio, with a mean of 36 (Table 2). Clostridium botulinum, Bacillus cereus, suspect yeasts and molds, Trichinella spiralis, paralytic shellfish poisoning, tin, caustic soda, rancid compounds and extraneous matter played lesser but significant roles in causing foodborne illness. No viruses were implicated during the 5 years, but this finding probably reflects more a lack of adequate epidemiological and laboratory procedures to follow up on possible foodborne viral infections than an actual lack of incidents. There were few deaths. The majority were caused by C. botulinum type E intoxication from consumption of game meat or fish left to age or mature under anaerobic conditions at ambient temperatures by native people (Table 4). This is a problem peculiar to northern Canada and Alaska and has to be improved by educating those who like this kind of food. Deaths from S. aureus-contaminated food, such as meat and egg salad, also occasionally occurred. The dangers of eating shellfish from areas where red tide algae occur (paralytic shellfish poison) and ingesting improperly cooked bear meat (Trichinella spiralis) were indicated not only by possibie severe illness but also by occa· sional death. Wnere information wa& known, all deaths resulted from mishandlIng 1ft the home (or out of doors) 0, in institutions Tor the eldeny.