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Further Information about Listeria and Listeriosis
ListeriosisListeriosis is an infection in humans caused by Listeria bacteria. These bacteria are widespread in nature. They are found in soil, dust, water, unwashed raw fruit and vegetables, fish, undercooked poultry, unpasteurised milk or dairy foods, soft cheeses, pate, prepared meats such as hot dogs and deli meats, and the faeces (poo) of domestic and wild animals.
Important Note: Being infected with listeria during pregnancy increases the risks of miscarriage, birth defects and illness in a baby.
This is uncommon, but if you have a flu-like illness during pregnancy, you should see your doctor as soon as possible.
The information that follows should not be used as a substitute for the medical care and advice of your health care provider.
What is listeriosis?
Listeriosis is an infection caused Listeria monocytogenes bacteria.
Listeria infections have only been recognised as a serious health problem over the last few years.
The bacterium is widespread so it is almost impossible to avoid it altogether.
It can grow in temperatures as low as 0.5 degrees C, but is easily destroyed by cooking.
Who is at risk?
Pregnant women. Even though listeriosis may not cause you to feel unwell at all, or only mildy unwell, there can be a serious risk to your unborn baby.
If you get listeria when you are pregnant there is a risk that your unborn baby will be infected. This can cause miscarriage or stillbirth or make your newborn baby very ill.
Avoiding high risk foods during pregnancy will make the risk to your baby much less. See the section below on Foods to avoid.
Others: People over 65 to 70 years are also at risk of a serious infection as are people with weakened immune systems (from illnesses such as diabetes, AIDS, cancer, kidney or liver disease), or from treatment which suppresses the immune system, such as cancer treatment, treatment after organ transplants).
How long listeria infections take to develop?
This varies between 3 and 70 days (mostly about 3 weeks). This means that it can sometimes be a long time after you have eaten the food containing the listeria bacteria before you actually get the illness.
Signs and symptoms
Most people with listeriosis have no illness at all and don't know they have it. It is a common infection but rarely causes problems.
If people are unwell, the infection causes flu-like symptoms, such as fever, headache, tiredness, aches and pains, and sometimes abdominal (tummy) cramps and diarrhoea. In rare cases it can cause meningitis or septicaemia.
Because it does not cause the same symptoms as other food poisoning (eg vomiting), listeriosis may not be recognised unless special tests are done.
Treatment
See your doctor. Listeriosis can be treated by antibiotics.
Listeriosis is reported to the health department so they can try to find the cause and protect other people from the infection
Protecting someone at risk from listeriosis
The main protections against listeriosis are
being very careful when preparing and storing food
avoiding foods that can contain listeria (See Foods to avoid below).
Care should be taken to keep cooked food and raw foods apart while preparing meals and in storage.
Knives, boards, plates, etc used for preparing raw food should be carefully washed in hot, soapy water and dried before using them for cooked food or food that will be eaten raw.
Raw food, especially meat should be wrapped and stored in the fridge below cooked food, so that juices cannot drip onto the cooked food.
Freshly prepared foods are the safest.
Avoid food that has passed its 'Use by' or 'Best before' date.
Fruit and vegetables eaten raw or in salads should be carefully washed.
Left-overs should be placed into the fridge straight away, and eaten within a day.
Cook foods fully. Listeria bacteria are easily destroyed by cooking.
Left-over meat and meat dishes should be kept cold in the fridge (less than 4�C), then reheated to steaming hot. If using a microwave oven, make sure that the food is reheated right through, not cold in the middle.
Frozen food should be thawed in the fridge or microwave, not at room temperature.
Pregnant women and other people at risk should avoid contact with sick or stillborn farm animals.
Foods to avoid
Because contact with listeria cannot be entirely escaped, at-risk people (such as pregnant women) should avoid eating foods that are likely to carry the germ. You should also avoid foods when you do not know how well they have been prepared.
Some examples of higher risk foods
Cold meats (unpackaged and sliced packaged meat)
Cold cooked chicken 'ready to eat'
Salads (fruit and vegetable salads) that have been prepared ahead of time (eg from salad bars or packaged)
Soft, semi-soft and surface ripened cheeses such as brie, camembert, ricotta, feta and blue cheeses (prepackaged cheeses as well as those sold in delis)
Un-pasteurised dairy products
Pate
Uncooked or smoked seafood and shellfish
Safer foods
Foods that have been fully cooked to 'steaming' hot and eaten hot (eg meat that has been 'well done' not 'rare')
Home cooked cold meat eaten within a day of cooking
Home cooked chicken. Store any left-overs in the fridge straight away and eat within one day
Freshly prepared salads. Wash fruit or vegetables before using them.
Store any leftovers in the fridge straight away and eat within a day
Freshly cooked seafood
Cheeses: hard cheese, processed cheese, cheese spread, plain cream cheese, plain cottage cheese
Pasteurised dairy products (milk, yoghurt, custard, packaged frozen icecream)
Canned foods.
References
Food Standards Australia and New Zealand, 'Listeria and food'
http://www.foodstandards.gov.au/_srcfiles/Listeria.pdf
Food Standards Australia and New Zealand 'Listeria and pregnancy' Fact sheet
http://www.foodstandards.gov.au/
Organisation of Teratology Information Services (OTIS) fact sheet, 'Listeriosis and pregnancy'
www.OTISpregnancy.org/pdf/listeriosis.pdf
South Australian Department of Health, Fact Sheet on Listeriosis. http://www.dh.sa.gov.au/pehs/Youve-got-wha...listeriosis.pdf
