Here are the answers to the main questions raised by the effect of this bacteria on health.^1-2 .

” The Listeria monocytogenes is a non-contagious bacterium, widespread throughout the environment, and not only in prepared foods, ”explains Jacinthe Perras, spokesperson for the Public Health Agency of Canada.

Thus, the bacteria can be found in:

• contaminated water, soil, vegetation;
• unwashed fruits and vegetables;
• undercooked meat, fish, unpasteurized dairy products, animal feed;
• faeces of humans and animals.

When consuming food contaminated with Listeria monocytogenes or come into contact with elements that are, it is possible to have listeriosis. “It is a notifiable disease in the provinces and, since 2006, in Canada as a whole,” explains Jacinthe Perras.

Listeriosis is not a rare disease, but it is not very common in the country: each year, there are approximately 150 cases per year.

“However, very young children, the elderly and people whose immune systems are weakened by disease are more vulnerable to listeriosis,” said the spokesperson for PHAC.

This infection can also be risky for pregnant women and also for the fetus, she adds. Listeriosis can cause spontaneous abortion, serious mental retardation, malformations and various health problems.

Symptoms of listeriosis are usually minor and can appear 2 to 30 days – and sometimes up to 70 days – after consuming the contaminated food.

The disease usually manifests with symptoms that resemble the flu or food poisoning:

• nausea
• vomiting
• abdominal cramps
• diarrhea
• headaches
• Constipation
• persistent fever

But in more vulnerable people, these symptoms may be followed by a brain or blood infection that can lead to death.

“We must not be alarmist, insists Jacinthe Perras. But if you believe that you have consumed infected products and that you experience acute and persistent symptoms, it is best to consult a doctor ”. The doctor can prescribe antibiotics if necessary.

The main way to prevent listeriosis is by following the basic rules of food safety and preparation.

Unlike other microorganisms, Listeria monocytogenes survives easily in refrigerated and saline environments (such as prepared meats and cold cuts).

You can be poisoned by the bacteria after consuming an infected food or after having been in contact with an infected surface or object, for example a cutting board or a knife.

“It is not easy to recognize a product that has been contaminated with Listeria monocytogenes : the food does not present any visible deterioration or a suspicious odor ”, specifies Ms. Perras.

By applying the following tips³, you will prevent not only listeriosis, but also other foodborne illnesses caused by bacteria Salmonella, E. Coli ou Campylobacter :

• Cook the minced meats completely.
• Avoid raw meat (tartare, carpaccio) as well as raw or smoked fish.
• Opt for pasteurized dairy products rather than those made with raw milk.
• Avoid raw hot dog sausages, soft cheeses (feta, brie, camembert, blue) and uncooked products such as salami and prosciutto.
• Give preference to prepackaged products under safe and controlled conditions. Make sure the packaging is intact.
• Store foods in the refrigerator at 4 ° C (40 ° F) or less.
• Wash vegetables and fruit thoroughly with potable water. Avoid those that cannot be washed (eg alfalfa sprouts or radish).
• Avoid bringing cooked food into contact with raw food. Pay particular attention to cooking juices and meat wrappers that leak blood.
• Wash hands thoroughly with soap, before and after handling food. Disinfect work surfaces and utensils that have been in contact with raw food.

Several strains of Listeria monocytogenes can cause listeriosis, but it is estimated that one of them is responsible for half of the cases. The latter is resistant to high temperatures as well as to cleaning agents.

“If you have any doubts about a food, don’t run any risk: throw it away! », Advises Jacinthe Perras.

Martin LaSalle – PasseportSanté.net

1. You can also consult the “Questions and Answers” ​​document posted online by the Public Health Agency of Canada on listeriosis: www.phac-aspc.gc.ca [accessed August 26, 2008].

2. For the list of products affected by the Canadian Food Inspection Agency’s recall: www.inspection.gc.ca [accessed August 26, 2008].

3. From the guide Eat better, for pleasure and health, Collection Protégez-Vous, in partnership with PasseportSanté.net and Extenso, 2007. For more information: www.extenso.org [consulted on August 26, 2008].