What is Listeriosis
Listeriosis is a serious infection Which is caused by eating food contaminated with the
bacterium Listeria monocytogenes.
It has recently been recognized as an important public health problem
in Canada and the United States.
The disease affects primarily persons of advanced age, pregnant women, newborns, and adults with
weakened immune systems. However, persons without these risk factors can also rarely be affected.
The risk may be reduced by following a few simple recommendations.
In veterinary medicine, however, listeriosis can be a quite common condition in some farm
outbreaks. It can also be found in wild animals.
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How great is the risk for listeriosis?
In the United States, an estimated that over 2,000 persons become seriously
ill with listeriosis each year. Of these, appox. 500 die.
People with increased risk are:
- Pregnant women - They are about 20 times more likely than other healthy
adults to get listeriosis. About one-third of listeriosis cases happen during
pregnancy.
- Newborns - Newborns rather than the pregnant women themselves suffer the
serious effects of infection in pregnancy.
- Persons with weakened immune systems
- Persons with cancer, diabetes, or kidney disease
- Persons with AIDS - They are almost 300 times more likely to get
listeriosis than people with normal immune systems.
- Persons who take glucocorticosteroid medications
- The elderly
Healthy adults and children occasionally get infected with
Listeria, but they rarely become seriously ill.
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How does Listeria Bacteria get into food?
Listeria monocytogenes is found in water and soil.
Vegetables can become contaminated from the soil and from manure used as
fertilizer.
Animals can carry the bacterium without appearing ill and can contaminate foods
of animal origin such as meats and dairy products.
The bacteria has been found in a variety of raw foods, such as uncooked meats and
vegetables, as well as in processed foods that become contaminated after processing, such as soft
cheeses and cold cuts at the deli counter. Unpasteurized (raw) milk or foods made from
unpasteurized milk may also contain the bacteria.
Listeria is killed by pasteurization and cooking; however, in certain ready-to-eat
foods such as hot dogs and deli meats, contamination may occur after cooking but before
packaging.
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How do you contract
listeriosis?
You get listeriosis by eating food contaminated with Listeria. Babies
can be born with listeriosis if their mothers eat contaminated food during pregnancy.
Although healthy persons may consume contaminated foods without becoming ill,
those at increased risk for infection can probably get listeriosis after eating food contaminated
with even a few bacteria. Persons at risk can prevent Listeria infection by avoiding
certain high-risk foods and by handling food properly.
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How can you reduce your risk for
listeriosis?
Recommendations:
Thoroughly cook raw food from animal sources, such as beef, pork, or poultry.
Thoroughly wash raw vegetables before eating.
- Keep uncooked meats separate from vegetables and from cooked foods and ready-to-eat
foods.
- Avoid unpasteurized (raw) milk or foods made from unpasteurized milk.
- Wash hands, knives, and cutting boards after handling uncooked foods.
- Consume perishable and ready-to-eat foods as soon as possible
Recommendations for people at high risk, such as pregnant women and people with
low or weak immune systems, in addition to the recommendations listed above.
Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until steaming
hot.
Avoid getting fluid from hot dog packages on other foods, utensils, and food preparation
surfaces, and wash hands after handling hot dogs, luncheon meats, and deli meats.
Do not consume soft cheeses such as feta, Brie, and
Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and
Panela, unless they have labels that clearly
state they are made from pastuerized milk.
Do not consume refrigerated pates or meat spreads. Canned or shelf-stable pates and meat spreads
may be eaten.
Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish, such as a
casserole.
Refrigerated smoked seafood, such as salmon, trout,
whitefish, cod, tuna or mackerel, is most often labeled as "nova-style," "lox," "kippered,"
"smoked," or "jerky." The fish is found in the refrigerator section or sold at deli counters of
grocery stores and delicatessens. Canned or shelf-stable smoked seafood may be
eaten.
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Can listeriosis be prevented?
The general guidelines recommended for the prevention of listeriosis are similar
to those used to help prevent other foodborne illnesses, such as salmonella. In addition, there are
specific recommendations for persons at high risk for listeriosis.
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What are the symptoms?
- Symptoms include: flu-like symptoms, nausea, vomiting, cramps, diarrhea, headache,
constipation and persistent fever.
- Symptoms usually appear within 2 to 30 days and sometimes up to 70 days after consuming
contaminated food.
- The very young, elderly or people with poor immune systems are the most at risk.
- Flu-like symptoms may be followed by a brain or blood infection, either of which can result
in death.
- A woman who develops listeriosis during the first three months of pregnancy could miscarry.
If she develops listeriosis later in the pregnancy, her baby may be stillborn or acutely
ill.
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How can you protect yourself and your
family?
- Keep foods out of the temperature danger zone (between 4°C and 60°C or 40°F and 140°F). Keep the refrigerator at
4°C (40°F) or colder.
Refrigerate food promptly.
- Thoroughly cook or boil foods such as hot dogs and poultry products until they are steaming
hot.
- Avoid raw, unpasteurised milk or foods made from raw milk or cheese.
- Buy only as much product as will be consumed in 1 to 2 days.
- Thoroughly wash raw vegetables before eating.
- Always wash your hands before, during and after handling any type of food. Especially raw
meat and poultry.
- Clean all utensils, such as, cutting boards and work surfaces with a mild bleach solution
(5 ml/1 tsp. bleach per 750
ml/3 cups water) before and after using.
- Separate utensils for raw and cooked foods.
- Follow “use by” dates especially on packaged goods with a long shelf life.
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How do you know if you have
listeriosis?
At the moment there is no routine screening test for listeriosis during pregnancy,
as there is for rubella and some other congenital infections.
If you have symptoms such as a fever or stiff neck, consult your doctor.
A blood or spinal fluid test (to cultivate the bacteria) will show if you have
listeriosis. During pregnancy, a blood test is the most reliable way to find out if your
symptoms are due to listeriosis.
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Can listeriosis be treated?
When infection occurs during pregnancy, antibiotics given promptly to the pregnant
woman can often prevent infection of the fetus or newborn.
Babies with listeriosis receive the same antibiotics as adults, although a combination of
antibiotics is often used until physicians are certain of the diagnosis. Even with prompt
treatment, some infections result in death. This is particularly likely in the elderly and in
persons with other serious medical problems.
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What is the government doing about
listeriosis?
Government agencies and the food industry have taken steps to reduce contamination
of food by the Listeria bacterium. The Food and Drug Administration and the
U. S. Department of Agriculture monitor
food regularly. When a processed food is found to be contaminated, food monitoring and plant
inspection are intensified, and if necessary, the implicated food is recalled.
The Coordinating
Center for Infectious Diseases (CCID) is studying listeriosis in several states to
help measure the impact of prevention activities and recognize trends in disease occurrence. CCID
also assists local health departments in investigating outbreaks. Early detection and reporting of
outbreaks of listeriosis to local and state health departments can help identify sources of
infection and prevent more cases of the disease.
In Canada:
For more information on foodborne illness and safe food handling practices, visit
the Canadian Food Inspection Agency website at www.inspection.gc.ca
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