What is Listeriosis?
Listeriosis is a serious bacterial disease caused by the Gram-positive, rod shaped bacterium, Listeria monocytogenes. The bacterium is widely distributed in nature and can be found in soil, water and contaminated food. Animals and food products such as vegetables can become contaminated from these sources. Infection with Listeria usually results in gastro-enteritis with symptoms ranging from mild to severe. However, in persons with weak immunity, Listeriosis can lead to meningitis or septicaemia. In pregnant women, Listeriosis may results in preganancy loss (abortion) along with meningitis of their infant.
Who can get Listeriosis?
Anyone can get Listeriosis. However, those at high risk of severe disease are newborns, the elderly, immunocompromised individuals, pregnant women and their unborn babies; and those with underlying conditions such as HIV, diabetes, cancer, chronic liver or kidney disease.
Where does Listeriosis occur in South Africa?
The first documented outbreak of listeriosis was from August 1977 to April 1978 where 14 cases from the Johannesburg area were reported. Sporadic cases occur throughout South Africa. In January to September 2015, seven cases were reported from a tertiary hospital in the Western Cape Province. No common source of exposure was found amongst these cases, although at least five of the seven were shown to be related on laboratory examination.
Listeriosis is usually spread through the ingestion of contaminated food products most frequently with raw or unpasteurised milk and soft cheeses, but also vegetables, processed foods, ready-to-eat meats and smoked fish products. Listeria can survive in normal temperatures associated with refrigeration (4C). The Listeria bacterium can also be transmitted from a pregnant woman to her unborn baby during pregnancy or at the time of birth. Direct contact with the organism can cause skin lesions.
The incubation period varies and can be between 3 70 days (median 3 weeks). Up to 10% of people may be asymptomatic carriers. This figure may be higher in abattoir and laboratory workers who work with Listeria monocytogenes cultures. In the average healthy adult, infection is usually asymptomatic. Symptoms are usually mild and may include fever, myalgia, malaise and sometimes nausea or diarrhoea. In at-risk patients, spread of infection to the nervous system can cause meningitis leading to headaches, confusion, stiff neck, loss of balance or convulsions. Bacteraemia may also occur.
Pregnant women may present with mild flu-like illness associated with headache, fever and myalgia. However, infections during pregnancy can lead to premature births, infection of the newborn with permanent disability, and miscarriage or stillbirth.