Listeria monocytogenes infection or listeriosis is a food-borne illness that can be contracted by eating contaminated food. The food poisoning occurs due to colonization with bacteria known as Listeria monocytogenes bacteria.
Here is a detailed guide to listeria and pregnancy, how you can reduce your risk of contracting these harmful bacteria.
Who is at higher risk of contracting listeriosis?
The following groups are most susceptible:
Pregnant women and their unborn babies
When listeria infection occurs during pregnancy, the consequences for pregnant women and especially their unborn babies can be devastating: miscarriage, preterm labor, and nervous system birth defects in unborn babies. Not all babies whose mothers are infected will develop a fetal infection or problems related to their mother’s listeria infection.
The Centers for Disease Control and Prevention (CDC) in the US report that pregnant Hispanic women are 24 times more likely to get listeria than other healthy adults.
Research shows that neonatal listeriosis is a very serious infection that can cause neonatal meningitis and sepsis.
Early diagnosis and treatment of the pregnant woman might help prevent infection and complications for the unborn baby.
Old people’s immune systems are usually weaker and therefore they’re more prone to infections and illnesses. They might be in need of help when preparing their meals and better education about perishable foods. Social workers often make sure these food safety educational programs are in place when an elderly person lives alone.
Anyone with a weakened immune system
Some serious infections or diseases, such as cancer or diabetes, weaken the immune system, leaving those who suffer from them at a higher risk of being affected by infection.
If you are in this group, be extremely careful about food safety to avoid listeria infections, and be extra cautious if any listeria outbreaks happen in your area. The Centers For Disease Control and Prevention usually have a list of those most at risk when serious infectious outbreaks occur. Double-check with them to see whether you’re on the list.
Anyone on medications that can suppress the immune system
Corticosteroids and other medications can suppress your immune system. Make sure to talk to your doctor about special safety measures when a pharmacological treatment is prescribed.
Organ transplant patients
People in this group have weaker immune systems, due to the drugs they take. When they are discharged home they’re always given simple food safety guidelines to make sure they minimize the risk of food poisoning.
Where are listeria bacteria found?
Listeria bacteria can be found in soil, silage, and sewage. They have also been found in foods, including raw meat, raw vegetables, and some processed foods. Outbreaks of listeria infection have been reported after people have eaten contaminated soft cheeses, milk, coleslaw, hot dogs, and meat spreads.
As listeria bacteria are commonly found in the environment, they are impossible to eradicate. Some exposure to the bacteria is unavoidable. Most people are, however, at low risk of listeria infection.
Listeria – foods to avoid in pregnancy
- Unpasteurized milk. These days, unpasteurized milk isn’t found in any shops and if you can find it it’s well labelled as being unpasteurized. We need to be cautious about consuming soft cheeses, such as Mexican style cheeses (queso fresco or queso blanco) that might be made with unpasteurized milk
- Uncooked foods. Uncooked meats, such as carpaccio, or undercooked meats, meat spreads and luncheon meats can also carry more risk of causing food poisoning as they’re not fully cooked. Be careful with smoked seafood, even if it’s refrigerated smoked seafood; it’s never been cooked and bacteria can grow in it more easily
- Uncooked vegetables. You always have to be extra careful when eating raw produce. Make sure you wash your vegetables thoroughly and add a drop of chlorine preparation to the water you soak your veggies in
- Contaminated foods. Be very careful with food stalls selling hot dogs, sandwiches and so on. Make sure you trust the place and that the food is steaming hot before you consume it.
Symptoms of listeria and pregnancy
Listeriosis symptoms differ in those affected; healthy people might develop no symptoms or have flu-like symptoms. For others, the infection can become serious enough to require hospitalization and can threaten life.
In persons at increased risk, such as pregnant women, symptoms might include:
- Upset stomach
- Muscle aches
These symptoms can progress to more serious symptoms, such as meningitis (a brain infection) and septicemia (blood poisoning). Less common symptoms of listeriosis include diarrhea, nausea, and abdominal cramps. In pregnant women, listeriosis is usually a mild illness; a high temperature before or during labor might be the only indicator that you have listeriosis. However, even a mild form of the illness can affect an unborn baby. It can lead to miscarriage, stillbirth, premature birth, or a baby who is very ill at birth.
How common is listeria in pregnancy?
Listeriosis is fairly uncommon but the fatality rate amongst those at higher risk of the illness is high. In Victoria, Australia, between 8 and 24 cases of listeria infection are reported to the Department of Human Services annually.
How to treat listeria in pregnancy?
Listeria infection can be treated with antibiotics, if treatment is started early. It is sometimes impossible, however, to determine which particular food has caused a person’s illness, as symptoms can take 3 to 70 days to appear after eating the contaminated food.
What can I do to reduce the risk of infection?
Avoid high-risk foods and always practice good food handling and hygiene. High-risk foods include the following:
- Ready-to-eat seafood (eg. smoked fish, smoked mussels, oysters, or raw seafood such as sushi)
- Pre-made salads, including coleslaw
- Pre-cooked meat products that do not require further cooking or heating (eg. paté, sliced deli meats, and cooked diced chicken)
- Unpasteurized milk or foods made from unpasteurized milk
- Soft serve ice-cream
- Soft cheeses (eg. brie, camembert, ricotta, and blue-veined cheeses); you can eat soft cheeses safely, however, if they are cooked and served hot
- Egg dishes; make sure the egg is completely cooked.
It is perfectly fine to eat the following foods:
- All freshly cooked foods
- Hard cheeses, cheese spreads, processed cheese
- Milk – freshly pasteurized milk and preferably long-life
- Canned and pickled food.
Good food handling and safe storage of food are important for everyone but especially important for those in the higher risk groups. Reduce the risk of developing listeriosis and other food-borne illnesses by following some basic food hygiene and food storage rules, including these:
- Wash your hands before preparing food and between handling raw and ready-to-eat foods
- Keep all food covered
- Place all cooked food in the refrigerator within one hour of cooking
- Refrigerate raw meat, raw poultry, and raw fish below cooked or ready-to-eat foods to prevent any drips from contaminating these foods
- Keep your refrigerator clean and the temperature below 5°C
- Strictly observe use-by or best-by dates on refrigerated foods
- Do not handle cooked foods with the same implements (tongs, knives, cutting boards) used on raw foods, unless they have been thoroughly washed with hot soapy water between uses
- Wash raw vegetables and fruit well before eating
- Don’t let food defrost on the kitchen sink; defrost food by placing it on the lower shelves of a refrigerator or using a microwave oven
- Thoroughly cook all animal products, including eggs, before eating them
- Keep hot foods hot (above 60°C) and cold foods cold (at or below 5°C)
- Reheat food until the internal temperature of the food reaches at least 70°C. You can purchase a food thermometer from your supermarket or variety store
- When using a microwave oven, read the manufacturer’s instructions carefully and observe the recommended standing times, to ensure the food attains an even temperature before it is eaten.
Unlike most other food-contaminating bacteria, listeria can grow in the refrigerator. Listeria bacteria, however, are readily killed during cooking. At-risk people can further reduce their risk by:
- Eating only freshly prepared foods
- Re-heating left-over foods till piping hot
- Avoiding dips and salad dressing in which vegetables might have previously been dipped
- Avoiding ready-to-eat foods that have been refrigerated for more than a day
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