Food Poisoning

Food poisoning includes intoxication and infection resulting from consumption of foods contaminated by toxins (poisons) produced by specific micro-organisms, or the presence of infectious micro-organisms, heavy-metal contaminants (eg, copper) or natural toxins. Food poisonings are generally characterized by gastrointestinal disorders and occasionally result in death. In Canada, approximately 1000 outbreaks, involving 5000-6000 cases, are reported annually. This figure probably represents 1% of actual cases. Most cases go unreported or are attributed to "24-hour flu." Most outbreaks in Canada are associated with meats and poultry, the principal cause being severe mishandling of food, especially improper cooling and inadequate reheating.

Staphylococcal ("staph") food intoxication is most common. It is caused by a heat-stable toxin produced by some strains of Staphylococcus aureus bacteria. Symptoms, including cramps, nausea, vomiting and diarrhea, begin in 1-6 hours and last for 24 hours. Of growing concern is salmonellosis, Salmonella food infection, especially associated with poultry and egg products but also with many other foods, from spices to chocolate candy. Symptoms, including cramps, chills, vomiting, diarrhea and fever, begin in 8-24 hours and last 2-3 days or longer. Infected persons often become asymptomatic carriers of Salmonella. In the aged, infirm or infants, salmonellosis can result in death.

A few outbreaks involving many cases of Clostridium perfringens, ie, perfringens poisoning or "institutional" food poisoning, occur annually. Symptoms are mild, including abdominal cramps and diarrhea. Food contaminated with C. botulinum may contain a neurotoxin that causes the rare but severe form of food poisoning, botulism. Food poisonings associated with Escherichia coli, Yersinia enterocolitica and other bacteria are uncommon in Canada. Heavy metals account for less than 1% of outbreaks.

During the 1970s, Campylobacter jejuni was identified as a major cause of human gastroenteritis. Campylobacter are frequently found in poultry meat, but thus far outbreaks of campylobacterosis from foods have only been associated with unpasteurized milk and untreated water supplies. Each year outbreaks of trichinosis, ie, infestation by the parasite Trichinella spiralis, occur from ingestion of undercooked meats, especially pork, and wild game such as bear meat.

See also Hamburger Disease.