What is Listeria?

Listeria is a common bacterium (bug) which is widely found in dust, soil, water, plants, sewage and animal droppings.

How does it affect humans?

Listeria is only dangerous to pregnant women, their babies and people with a lowered immune system. Almost all other people are not harmed by it. If a pregnant woman develops an infection caused by Listeria (listeriosis), it can cause miscarriage and stillbirth. Newborn babies who develop listeriosis can have difficulty breathing, develop a chest infection and an inflammation of the coverings of the brain (meningitis). This can sometimes cause death.

What are the symptoms of listeriosis in pregnant women?

Listeriosis may cause no symptoms at all or you may feel like you have a mild dose of the flu. Symptoms include: a mild fever, headache, nausea, vomiting and aches and pains in your joints and muscles or a mild cough or cold.

Some women can become very sick with listeriosis and have a very high temperature. This increases the risk of your unborn child being infected.

How are pregnant women infected by Listeria?

Listeria can be transmitted to pregnant women by infected food. The bug has been found in a variety of foods at all stages of preparation, from raw to well cooked left-overs. Listeria will still grow on food which is stored in a fridge.

How do I prevent listeriosis?

The following foods are safe and nutritious to eat when pregnant:

• Most foods which have been thoroughly cooked (until piping hot) and eaten straight away.
• Vegetables and fruit which have been well washed.
• All tinned foods.
• Breads and cereals (without added mock creams or custards).
• Dried food (fruit, nuts, lentils, beans etc).
• Pasteurised milk and milk products - yoghurt, cheese etc.

Do not eat the following foods:

• Chilled pre-cooked seafood products, unless eaten hot.
• Pate, pre-cooked chicken, ham and other chilled pre-cooked meat products. Cook any left-over foods or ready-to-eat foods, such as hot dogs, until steaming hot before eating.
• Uncooked seafoods.
• Stored salads and coleslaws, especially from delicatessens or supermarkets.
• Raw (unpasteurised) milk or foods made from raw milk.

Safe ways to handle food at home

• Keep uncooked meats separate from vegetables, and from cooked foods and ready-to-eat foods. Uncooked meats should also be well wrapped or covered.
• Wash hands, knives, and cutting boards thoroughly with hot water and soap after handling uncooked foods.
• Cook left-over foods or ready-to-eat foods, such as hot dogs, until steaming hot before eating.
• Take special care when using a microwave to heat foods all the way through until it is piping hot.
• Wash all fresh food carefully before eating it.

More information

The NZ Food Safety Authority (NZFSA) also produces a booklet, Food safety in pregnancy, available free from the NZFSA website or by phoning 0800 693 721.

You can also talk to your doctor or midwife and contact the Public Health Units at your local Community Health Service.

Written by Anna Mickell RCpN. Reviewed by everybody.