Canadian Partnership for Consumer Food Safety Education

The Causes of Foodborne Illness

What is foodborne illness?

Foodborne illness occurs when a person gets sick from eating food that has been contaminated with an unwanted micro-organism or pathogen. This condition is often called "food poisoning". Bacteria, parasites and viruses are microorganisms that can cause foodborne illness. Many cases of foodborne illness go unreported because their symptoms often resemble the stomach flu. The most common symptoms of foodborne illness include stomach cramps, nausea, vomiting, diarrhea and fever.

What are the most common pathogens that can cause foodborne illness?

Clostridium botulinum

  • In adults, Clostridium botulinum (C. botulinum) itself does not make people ill, but the poisons produced by the pathogen do.
  • Canned (especially home canned) low acid foods may contain C. botulinum, but some cases occur after eating aged meats from marine mammals.
  • Symptoms can include double vision, nausea, vomiting, fatigue, dizziness, headache and dryness in the throat and nose. In extreme cases, symptoms may progress to respiratory failure.

Campylobacter

  • Campylobacter is a bacteria commonly found in the intestines of poultry, cattle, swine, rodents, wild birds and such household pets as cats and dogs. It can also be found in untreated water.
  • People may develop a Campylobacter infection when they eat undercooked poultry or drink raw milk or non-chlorinated water.
  • Symptoms of Campylobacter can include fever, headache and muscle pain, followed by diarrhea, stomach pain, nausea, and Guillain-Barré Syndrome.

Cyclospora

  • Cyclospora is a microscopic parasite that infects the small intestine of humans.
  • Cyclospora is transmitted through food or water contaminated by infected feces. Although Cyclospora is not naturally found on fresh fruits and vegetables, contamination may occur during cultivation, harvest, packaging or transportation through contact with contaminated water or workers.
  • Symptoms of Cyclospora may include diarrhea, loss of appetite, weight loss, nausea, gas, stomach cramps, muscle ache, vomiting and low-grade fever.

Escherichia coli 0157:H7

  • Escherichia coli O157:H7 bacteria live in the intestines of animals such as cattle, pigs, sheep and poultry. Despite precautions, when these animals are butchered, the bacteria can spread to the outer surfaces of the meat. When meat is ground, the grinding process can spread bacteria through the meat.
  • E. coli O175:H7 may also be found in undercooked meat and poultry, on raw fruits and vegetables, including sprouts, untreated water, unpasteurized milk and raw milk cheeses, unpasteurized apples juices and ciders and petting zoos.
  • Symptoms of E.coli include minor flu-like symptoms to more severe stomach cramps, vomiting and fever, and even kidney failure.

Listeria

  • Listeria is a type of bacteria often found in soil, vegetation, fodder, and human/animal feces.
  • Listeria can be contracted by eating dairy products, vegetables, fish and meat products that are contaminated with the bacteria.
  • Symptoms can start with flu-like nausea, vomiting, cramps, and fever; however, the most severe symptoms can result in a brain or blood infection either of which can lead to death. A woman developing listeriosis during the first three months of her pregnancy may miscarry. If she develops listeriosis later in pregnancy; her baby may be stillborn or acutely ill.

Clostridium perfringens

  • Clostridium perfringens (C. perfringens) is a spore-forming bacterium which produces a toxin in the intestinal tract of people who have eaten food containing high levels of the bacteria.
  • This organism can be found in high protein or starch-like foods such as cooked beans or gravies and is especially likely to be a problem in improperly handled leftovers.
  • Symptoms consist of very gassy diarrhea, cramps and headache.

Salmonella

  • Salmonella is a bacteria found in the intestines of animals. Foods or environments contaminated with animal waste may contain Salmonella bacteria. It has also been found in a low percentage of unbroken raw eggs.
  • Raw poultry is the most common food that may contain Salmonella. Other foods include raw and undercooked meats, un-pasteurized milk and eggs. Fruits and vegetables may also contain the bacteria, if they have been in soil contaminated with animal waste.
  • Symptoms range from mild diarrhea, abdominal cramps, vomiting and fever to severe dehydration.

Toxoplasma

  • Toxoplasma is a microscopic parasite that may infect a wide variety of birds and mammals, including humans. Infection occurs when there is ingestion of the Toxoplasma infective stages; either the oocysts or the tissue cysts found in some raw meats.
  • Improperly handling meat and eating undercooked meat may cause illness. Eating fruits and vegetables from gardens contaminated with cat feces may also result in the illness.
  • Symptoms can include slight fever, enlarged lymph nodes and other flu-like symptoms. People with weak immune systems may develop more severe symptoms such as pneumonia.

For more information on foodborne illness and steps you can take to reduce the risk, visit the Canadian Food Inspection Agency Web site.

This fact sheet was prepared by the Canadian Food Inspection Agency

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