Listeriosis is an infection caused by the bacterium Listeria monocytogenes “often referred to as Listeria”. This type of bacteria is found naturally in soil, sewage, stream water, on animals, plants and food. The bacteria naturally occur in the environment and then can be transferred into food production facilities, through things such as people’s shoes, crates, pallets, trolleys and forklifts. Because of this it is inevitable that Listeria may contaminate some food from time to time.
Listeriosis is generally only dangerous to high-risk populations such as pregnant women, unborn or newborn babies, elderly or individuals with compromised immune systems.
During pregnancy hormonal changes in the body, such as escalated production of progesterone, lower the immune system. This can make it harder to fight off illness and infections. Listeria can take advantage of this and cause the invasive listeriosis infection, with about one in ten listeriosis cases (10%) in Australia occurring in pregnant women.
Symptoms can take days or even weeks to appear and are similar to flu symptoms such as; fever, tiredness, headache, aches and pains, and less commonly nausea and diarrhoea. Unfortunately, the infection can progress to meningitis, septicaemia and encephalitis, which can be life-threatening. Intrauterine and cervical infections can also occur during pregnancy, which can result in stillbirths and spontaneous abortions. Listeria infections in people who do not fall within these categories may not even notice symptoms, or symptoms are often mistaken for a mild viral infection.
Because of this, food that is regarded as having a higher risk of containing the bacteria Listeria monocytogenes or other bacteria such as Salmonella, which also causes food poisoning, are advised not to be consumed in pregnancy. The foods to avoid include:
- soft and semi-soft cheeses
- cold pressed meats
- cold cooked chicken
- pre-prepared vegetables and salads
- pre-cut fruit
- soft-serve ice-cream
- raw seafood
While pregnant women should be careful about what they eat during pregnancy they also need to maintain a healthy diet. By understanding the level of risk that different foods pose, women can still maintain a varied and nutritious diet. If at any time you are concerned or are feeling unwell please consult Dr Bishop and the Maternity team at John Flynn Hospital.
For more information on listeria and food, please visit the following information pages: