What is listeriosis and how can we protect ourselves against it?

The other African countries listed as being at risk are Angola, Botswana, the Democratic Republic of Congo, Ghana, Lesotho, Madagascar, Malawi, Mauritius, Mozambique, Namibia, Swaziland, Tanzania, Uganda, Zambia and Zimbabwe.

What is listeriosis?

Listeriosis is a series of diseases caused by the bacteria L. monocytogenes, outbreaks of which occur in all countries. There are two main types of listeriosis: a non-invasive form and an invasive form.

Noninvasive listeriosis (febrile listerial gastroenteritis) is a mild form of the disease affecting mainly otherwise healthy people. Symptoms include diarrhoea, fever, headache and myalgia (muscle pain). The incubation period is short (a few days). Outbreaks of this disease have generally involved the ingestion of foods containing high doses of L. monocytogenes.

Invasive listeriosis is a more severe form of the disease and affects certain high risk groups of the population. These include pregnant women, patients undergoing treatment for cancer, AIDS and organ transplants, elderly people and infants. This form of disease is characterized by severe symptoms and a high mortality rate (20%–30%). The symptoms include fever, myalgia (muscle pain), septicemia, meningitis. The incubation period is usually one to two weeks but can vary between a few days and up to 90 days.

The initial diagnosis of listeriosis is made based on clinical symptoms and detection of the bacteria in a smear from blood, cerebrospinal fluid (CSF), meconium of newborns (or the fetus in abortion cases), as well as from faeces, vomitus, foods or animal feed. Various detection methods, including polymerase chain reaction (PCR), are available for diagnosis of listeriosis in humans. During pregnancy, blood and placenta cultures are the most reliable ways to discover if symptoms are due to listeriosis.

Pregnant women are about 20 times more likely to contract listeriosis than other healthy adults. It can result in miscarriage or stillbirth. Newborn may also have low birth weight, septicaemia and meningitis. People with HIV/AIDS are at least 300 times more likely to get ill than those with a normally functioning immune system.

Due to the long incubation period, it is challenging to identify the food which was the actual source of the infection.

What are the symptoms?

The symptoms of listeriosis include fever, muscle aches, and sometimes nausea or diarrhea. If infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can occur. But infected pregnant women may experience only a mild, flu-like illness.

How is listeriosis diagnosed?

Listeriosis is diagnosed based on a medical history and physical exam. Your doctor will ask you questions about your symptoms, foods you have recently eaten, and your work and home environments. A blood test or spinal fluid test may be done to confirm the diagnosis.

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How is it treated?

An otherwise healthy person who is not pregnant typically does not need treatment. Symptoms will usually go away within a few weeks.

If you are pregnant and get listeriosis, antibiotics can often prevent infection of the foetus or newborn. Babies who have listeriosis receive the same antibiotics as adults, although a combination of antibiotics is often used until your doctor is certain the cause is listeriosis.